Microbial fermentation method for production of n-acetyl-d-glucosamine and/or d-glucosamine salt

Abstract

This Invention discloses a method for production of N-Acetyl-D-Glucosamine and/or D-Glucosamine Salt by microbial fermentation. The method is intended to manufacture N-Acetyl-D-Glucosamine and/or D-Glucosamine Salt in higher efficiency and higher yield, by expression of vitreoscilla hemoglobin in microorganism.

Claims

1. A method for production of N-Acetyl-D-Glucosamine and/or D-Glucosamine by microbial fermentation, including: a) Cultivation of a microorganism in the fermentation medium, where the said microorganism is transformed with a modified recombinant nucleic acid molecule encoding modified vitreoscilla hemoglobin (Vhb); wherein the modified nucleotide sequence encoding the said modified vitreoscilla hemoglobin (Vhb) contains a genetic modification to increases the activities of the vitreoscilla hemoglobin (Vhb) of the amino acid sequence of SEQ ID NO: 61; where the said modified vitreoscilla hemoglobin (Vhb) contain substitutions at the following sites of the amino acid sequence SEQ ID No: 61: methionine at site 45 is substituted by leucine, cysteine at site 86 is substituted by glycine, and tyrosine at site 95 is substituted by serine; and b) Collection of N-Acetyl-D-Glucosamine produced from the cultivation step a).

2. The method based on claim 1, wherein the nucleic acid sequence encoding the said vitreoscilla hemoglobin (Vhb) of the amino acid sequence of SEQ ID NO: 61 is SEQ ID NO: 64.

3. The method based on claim 1, wherein the microorganism is transformed with the modified recombinant nucleic acid molecule encoding the modified vitreoscilla hemoglobin (Vhb) using a natural endogenous promoter, or a promoter with a higher expression level than that of the natural endogenous promoter.

4. The method based on claim 1, where the said microorganism contains further genetic modifications: 1. Contain at least one genetic modification that may increase the effects of N-Acetyl-D-Mannosamine Kinase (NanK) in microorganism; 2. Contain at least one genetic modification that may increase the effects of N-Acetyl-D-Mannosamine-6-Phosphate Epimerase in microorganism; 3. Contain at least one genetic modification that may increase the effects of D-Glucosamine-6-Phosphate Deaminase in microorganism, and preferably contain at least one genetic modification that may decrease the effects of Glucosamine-6-Phosphate Synthase; 4. Contain at least one genetic modification that may increase the effects of D-Glucosamine-6-Phosphate Synthase in microorganism, and preferably contain at least one genetic modification that may decrease the effects of D-Glucosamine-6-Phosphate Deaminase; 5. Contain at least one genetic modification that may increase the effects of UDP-N-Acetyl-D-Glucosamine-2-Epimerase (WecB) in microorganism.

5. The method based on claim 1, where the said microorganism contains further genetic modifications: 1. Contain at least genetic modification that may decrease the effects of Mannose transporter EIIM, P/III.sup.man(ManXYZ) in microorganism; 2. Contain at least one genetic modification that may decrease the effects of N-Acetylneuraminate Lyase (NanA) in microorganism; 3. Contain at least one genetic modification that may decrease the effects of N-Acetyl-D-Glucosamine-6-Phosphate Deactylase (NagA) in microorganism; 4. Contain at least one genetic modification that may decrease the effects of N-Acetyl-D-Glucosamine Specific Enzyme II.sup.Nag(NagE) in microorganism; 5. Contain at least one genetic modification that may increase the effects of PhosphoGlucosamine Mutase (GlmM) in microorganism; 6. Contain at least one genetic modification that may increase the effects of bifunctional N-acetyl Glucosamine-1-Phosphate Uridyltransferase (GlmU) in microorganism.

6. The method based on claim 3, the promoter which shows the higher expression level than the natural endogenous promoter is selected from HCE promoter, gap promoter, trc promoter, and T7 promoter.

Description

DESCRIPTIONS FOR ATTACHED FIGURES

(1) FIG. 1, Biosynthesis Strategy and Metabolic Engineering Strategy for N-Acetyl-D-Glucosamine in Escherichia Coli

ACTUAL IMPLEMENTATION MODES

(2) Hereafter this Invention is further described detailedly in combination with the implementation examples. The following examples are just used as ones to clarify and explain this Invention, and cannot be explained as any limitation to the protection range of this Invention. The technology realized, based on the contents of this Invention, are covered in the protection range of this Invention.

(3) Unless otherwise specified, the raw materials and reagents used in the implementation examples are commercially available goods.

(4) The list of various modified microorganisms involved in and/or described by this Invention is provided below.

(5) TABLE-US-00001 Strain No. Genotype Description Remarks AT-001 ATCC 27325, F-IN(rrnD-rrnE)1 lambda-, a Parent strain of engineering prototrophic derivative strain of bacterial, obtained from Escherichia coli K-12 American Type Culture Collection (ATCC) AT-002-01 AT-001, .sup.Δ manXYZ::fKanrf Example 1 AT-002-02 AT-001, .sup.Δ manXYZ Example 1 AT-003-01 AT-002-02, .sup.Δ nanA::fKanrf Example 1 AT-003-02 AT-002-02, .sup.Δ nanA Example 1 AT-004-01 AT-003-02, .sup.Δ nagA::fKanrf Example 1 AT-004-02 AT-003-02, .sup.Δ nagA Example 1 AT-005-01 AT-004-02, .sup.Δ nagE::fKanrf Example 1 AT-005-02 AT-004-02, .sup.Δ nagE Example 1 AT-006-01 AT-004-02, .sup.Δ nagE::pTrc-nanK-fKanrf Example 2a AT-006-02 AT-004-02, .sup.Δ nagE::pTrc-nanK Example 2a AT-007-01 AT-004-02, .sup.Δ nagE::pTrc-nanKM-fKanrf Example 2b AT-007-02 AT-004-02, .sup.Δ nagE::pTrc-nanKM Example 2b AT-052 AT-007-02, vhb/pTrc99A Example 2.c AT-053 AT-007-02, vhbM/pTrc99A Example 2.c AT-030-01 AT-004-02, .sup.Δ nagE::pTrc-nanE-fKanrf Example 3.a AT-030-02 AT-004-02, .sup.Δ nagE::pTrc-nanE Example 3.a AT-031-01 AT-004-02, .sup.Δ nagE::pTrc-nanEM-fKanrf Example 3.b AT-031-02 AT-004-02, .sup.Δ nagE::pTrc-nanEM Example 3.b AT-054 AT-031-02, vhb/pTrc99A Example 3.c AT-055 AT-031-02, vhbM/pTrc99A Example 3.c AT-042-01 AT-004-02, .sup.Δ nagE::pTrc-wecB-fKanrf Example 4.a AT-042-02 AT-004-02, .sup.Δ nagE::pTrc-wecB Example 4.a AT-043-01 AT-004-02, .sup.Δ nagE::pTrc-wecBM-fKanrf Example 4.b AT-043-02 AT-004-02, .sup.Δ nagE::pTrc-wecB Example 4.b AT-056 AT-043-02, vhb/pTrc99A Example 4.c AT-057 AT-043-02, vhbM/pTrc99A Example 4.c AT-048 AT-005-02, .sup.Δ nagB promotor::Trc promoter Example 5.a AT-049 AT-048, .sup.Δ glmS promotor Example 5.a AT-050 AT-005-02, .sup.Δ glmS promotor::Trc promoter Example 5.b AT-051 AT-050, .sup.Δ nagB promotor Example 5.b AT-058 AT-049, vhb/pTrc99A Example 5.c AT-059 AT-049, vhbM/pTrc99A Example 5.c AT-060 AT-051, vhb/pTrc99A Example 5.c AT-061 AT-051, vhbM/pTrc99A Example 5.c AT-009 AT-007-02, .sup.Δ nanE promotor::Trc promoter Example 6 AT-062 AT-009, vhb/pTrc99A Example 6 AT-063 AT-009, vhbM/pTrc99A Example 6 AT-010 AT-007-02, .sup.Δ nagB promotor::Trc promoter Example 7 AT-011 AT-010, .sup.Δ glmS promotor Example 7 AT-012 AT-007-02, .sup.Δ glmS promotor::Trc promoter Example 7 AT-013 AT-012, .sup.Δ nagB promotor Example 7 AT-064 AT-011, vhb/pTrc99A Example 7 AT-065 AT-011, vhbM/pTrc99A Example 7 AT-066 AT-013, vhb/pTrc99A Example 7 AT-067 AT-013, vhbM/pTrc99A Example 7 AT-019 AT-007-02, .sup.Δ wecB promotor::Trc promoter Example 8 AT-068 AT-019, vhb/pTrc99A Example 8 AT-069 AT-019, vhbM/pTrc99A Example 8 AT-032 AT-031-02, .sup.Δ nagB promotor::Trc promoter Example 9 AT-033 AT-032, .sup.Δ glmS promotor Example 9 AT-034 AT-031-02, .sup.Δ glmS promotor::Trc promoter Example 9 AT-035 AT-034, .sup.Δ nagB promotor Example 9 AT-070 AT-033, vhb/pTrc99A Example 9 AT-071 AT-033, vhbM/pTrc99A Example 9 AT-072 AT-035, vhb/pTrc99A Example 9 AT-073 AT-035, vhbM/pTrc99A Example 9 AT-037 AT-031-02, .sup.Δ wecB promotor::Trc promoter Example 10 AT-074 AT-037, vhb/pTrc99A Example 10 AT-075 AT-037, vhbM/pTrc99A Example 10 AT-044 AT-043-02, .sup.Δ nagB promotor::Trc promoter Example 11 AT-045 AT-044, .sup.Δ glmS promotor Example 11 AT-046 AT-043-02, .sup.Δ glmS promotor::Trc promoter Example 11 AT-047 AT-046, .sup.Δ nagB promotor Example 11 AT-076 AT-045-02, vhb/pTrc99A Example 11 AT-077 AT-045-02, vhbM/pTrc99A Example 11 AT-078 AT-047-02, vhb/pTrc99A Example 11 AT-079 AT-047-02, vhbM/pTrc99A Example 11 AT-015 AT-011, .sup.Δ nanE promotor::Trc promoter Example 12 AT-017 AT-013, .sup.Δ nanE promotor::Trc promoter Example 12 AT-027 AT-015, .sup.Δ wecB promotor::Trc promoter Example 12 AT-029 AT-017, .sup.Δ wecB promotor::Trc promoter Example 12 AT-080 AT-027, vhb/pTrc99A Example 12 AT-081 AT-027, vhbM/pTrc99A Example 12 AT-082 AT-035, vhb/pTrc99A Example 12 AT-083 AT-035, vhbM/pTrc99A Example 12

Example 1

(6) This implementation describes construction of a mutant strain of Escherichia coli, for which the relevant metabolic pathways for intake of N-Acetyl-D-Glucosamine is blocked and degradation of beneficial intermediate products are blocked.

(7) The said parent strain of the production strain is AT-001 (Escherichia coli ATCC 27325), belonging to K-12 derivative strain of Escherichia coli, and is obtained from American Type Culture Collection.

(8) Blockage of intake of N-Acetyl-D-Glucosamine into the strain, and of degradation of intermediate products may reduce consumption during metabolism, and increase accumulation of the target product (N-Acetyl-D-Glucosamine).

(9) To construct such mutant host strain, manXYZ, nanA, nagA, and nagE gene sequences in its chromosomal genomes may be deleted completely or partially, to deactivate its function, and thus result in accumulation of N-Acetyl-D-Glucosamine.

(10) Such deletion of gene sequence in the chromosome may be accomplished by Red recombinant technology. Red recombination is an homologous recombination technology, based on Red operon in λ phage, and mediated by RecE/RecT system in Rac phage. By the technology, it may carry out simply and rapidly multiple modifications such as insertion, knockout, and mutation to any large DNA molecules. Simply speaking, for Red recombination technology, pKD46 plasmids with the recombinase-expressing gene are introduced into thalli, then the prepared linear DNA segment for targeting is electrotransformed, positive clones are screened, and finally the resistance gene in the strain is removed.

(11) The specific operational process is described hereafter:

(12) 1. Deletion of manXYZ gene sequence

(13) Mannose transporter EIIM, P/III.sup.man (mannose transporter EIIM, ManXYZ) may be used as a second transporter of N-Acetyl-D-Glucosamine; it may transport hexose such as N-Acetyl-D-Glucosamine into cells, and thus the target product excreted out of cells and accumulated is transported into cells for degradation. Deletion of manXYZ gene sequence may block transportation of extracellular N-Acetyl-D-Glucosamine into cells for degradation.

(14) (1) Preparation of Linear DNA Full-length PCR Segment for Targeting of Red Recombination

(15) 1) fKanrf segment amplified by PCR

(16) fKanrf, i.e. FRT-Kanr-FRT segment means a FRT site base sequence for specific recognition of FLP recombinase, mounted at both ends of kalamycin resistance gene (Kanr).

(17) Primer Design: Forward primer (mfKanf-F) SEQ ID No.1, and reverse primer (mfKanf-R) SEQ ID No.2.

(18) Template: pPic9K.

(19) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(20) fKanrf size: 1.28 kb. Its nucleotide sequence is SEQ ID No.3.

(21) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(22) 2) PCR Amplification of Linear DNA Full-length PCR Segment for Targeting of Red Recombination

(23) Design of Homologous Arm Primer: According to the manXYZ sequence SEQ ID No.4, it is designed to delete the homologous arm forward primer (manXYZKO-F) SEQ ID No.5 and reverse primer (manXYZKO-R) SEQ ID No.6 of the manXYZ sequence.

(24) Template: Amplification of fKanrf PCR Segment.

(25) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(26) Amplification Product: Homologous Arm+fKanrf+Homologous Arm.

(27) The PCR product is separated by agarose gel electrophoresis, and purified and recovered to obtain 100 ng/μL linear DNA full-length PCR segment for targeting of Red recombination.

(28) (2) Red Recombination Operation

(29) First, pKD46 carrier is introduced into the AT-001 strain of Escherichia coli. Then, the prepared linear DNA segment for targeting is electrotransformed, and positive clones are screened. Finally, the resistance gene is removed.

(30) 1) Transformation of pKD46 Plasmid

(31) pKD46 carrier is a plasmid with Red recombinase-expressing gene, which is 3-gene segment expressing Exo, Bet, and Gam; the 3 genes are placed below the arabinose promoter, and may express in a large amount by induction of L-arabinose. It is necessary to transform pKD46 plasmid into Escherichia coli, to achieve purpose to modify the target gene in the chromosome by Red recombination.

(32) {circle around (1)} Preparation of Competence: First, inoculate the bacterial suspension of Escherichia coli ATCC 27325 stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h. then add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min. Finally, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation. Here, preparation of 0.1M CaCl.sub.2: Prepare a 1M CaCl.sub.2 solution with anhydrous CaCl.sub.2, autoclave at a steam pressure of 15 lbf/in2 for 20 min, and dispense 1.5 mL and store at −20° C.; for use, allow to thaw, and then dilute in a ratio of 1:10 to produce a 0.1M CaCl.sub.2 solution.

(33) {circle around (2)} Plasmid Transformation: Transfer 250 μL of spontaneously sedimented thalli, add 5 μL of pKD46 plasmid, and cultivate at −4° C. for 30 min. Then heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h. Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate. Cultivate overnight (for 12-16 h) at 30° C. Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification. Store the positive strain for use.

(34) 2) Electrotransform linear DNA segment for targeting, and screen positive clone

(35) {circle around (2)} Preparation of electrotransformed competence: Inoculate the AT-001 strain of Escherichia coli ATCC 27325, containing pKD46, into a test tube of LB medium containing Ampicillin (Amp), and shake-cultivate overnight at 250 rpm; On the next day, inoculate in a ratio of 1% into LB medium containing Amp, and cultivate at 30° C.; when OD.sub.600 reaches approximately 0.2, add 0.2% L-Arabinose, and induce at 30° C. for 35 min until OD.sub.600 reaches approximately 0.4. Cool on an ice bath. Wash once with ultrapure water, wash twice with 10% glycerin, and finally resuspend with 10% glycerin; the amount of glyerin used is to produce a final concentration of the thalli concentrated by 500-1000 folds.

(36) {circle around (2)} Transformation by electric shock: Take out a 2-mm electrotransformation cup from 70% ethanol, wash with sterilized ultrapure water, and irradiate by UV lamp for 30 min. Precool at 4° C. for 30 min. Transfer 90 μL of finally resuspended cells to a precooled centrifuge tube, add 5 μL (more than 100 ng) of the full-length PCR segement (linear DNA) obtained in Step (1), suction gently by a gun, and maintain on an ice bath for 30 min. Electrotransformation Parameters: 2500V, 200Ω, 25 μF.

(37) {circle around (3)} Resuscitate and screen positive clones: add 1 mL of LB broth medium, and cultivate at 37° C. and 100 rpm for 1 h. Then smear one kanamycin (Kan) plate with every 200 μL, 5 plates in total. Smear evenly and allow to air-dry. Cultivate at 30° C. for 24 h. Pick up clones grown under kanamycin resistance, and carry out PCR identification to screen positive clones.

(38) No. of the obtained strain: AT-002-01 (AT-001, Δ manXYZ::fKanrf).

(39) (3) Removal of the Resistance Gene

(40) To facilitate subsequent work, the resistance gene in the obtained strain (positive clones) may be removed. Removal of the resistance gene may be accomplished by pCP20 plasmid. pCP20 is a plasmid with ampicillin and chloramphenicol resistance genes, and may express FLP recombinase after thermal induction, which may identify specifically FRT sites. The sequence between FRT sites may be deleted by recombination, to retain only one FRT site.

(41) Introduce pCP20 into the above kanamycin-resistant clones, cultivate at 30° C. for 8 h, then increase to 42° C. and cultivate overnight, and thermally induce to express FLP recombinase; the plasmids are lost gradually. Streak the plate of antibiotics-free culture medium by an inoculating loop dipped in the bacterial suspension, pick up grown monoclones and dot on the kanamycin-resistant plate; those that cannot grown are clones of which the kanamycin resistance gene has been removed by FLP recombination. Carry out PCR with identification primer to identify clones losing kanamycin resistance.

(42) No. of the obtained strain: AT-002-02 (AT-001, Δ manXYZ).

(43) 2. Deletion of nanA Gene Sequence

(44) N-Acetylneuraminate Lyase (N-acetylneuraminate lyase, NanA) can degrade N-Acetyl-D-Mannosamine (ManNAc) in microorganism to produce N-Acetyl-D-Neuraminic Acid (Neu5Ac). Deletion of the nanA gene sequence in nanKETA operon may block degradation of N-Acetyl-D-Mannosamine (ManNAc) into N-Acetyl-D-Neuraminic Acid (Neu5Ac).

(45) (1) Preparation of Linear DNA Full-length PCR Segment for Targeting of Red Recombination

(46) Design of Homologous Arm Primer: According to the nanA sequence SEQ ID No.7 in the former segment of nanE-nanK, the homologous arm primers for deletion of nanA sequence are designed: Forward primer (nanAKO-F) SEQ ID No.8 and reverse primer (nanAKO-R) SEQ ID No.9.

(47) Template: Amplification of fKanrf PCR Segment.

(48) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(49) Amplification Product: Homologous Arm+fKanrf+Homologous Arm.

(50) The PCR product is separated by agarose gel electrophoresis, and purified and recovered to obtain 100 ng/μL linear DNA full-length PCR segment for targeting of Red recombination.

(51) (2) Red Recombination Operation

(52) First, pKD46 carrier is introduced into the AT-002-02 strain of Escherichia coli. Then, the prepared linear DNA segment for targeting is electrotransformed, and positive clones are screened. Finally, the resistance gene is removed.

(53) 1) Transformation of pKD46 Plasmid

(54) {circle around (1)} Preparation of Competence: First, inoculate the bacterial suspension of Escherichia coli AT-002-02 (AT-001, Δ manXYZ) stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h. then add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min. Finally, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(55) {circle around (2)} Plasmid Transformation: Transfer 250 μL of spontaneously sedimented thalli, add 5 μL of pKD46 plasmid, and cultivate at −4° C. for 30 min. Then heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h. Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate. Cultivate overnight (for 12-16 h) at 30° C. Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification. Store the positive strain for use.

(56) 2) Electrotransform linear DNA segment for targeting, and screen positive clone

(57) {circle around (1)} Preparation of Electrotransformed Competence: Inoculate the AT-002-02 strain of Escherichia coli, containing pKD46, into a test tube of LB medium containing Ampicillin (Amp), and shake-cultivate at 250 rpm. On the next day, inoculate in a ratio of 1% into LB medium containing Amp, and cultivate at 30° C.; when OD.sub.600 reaches approximately 0.2, add 0.2% L-Arabinose, and induce at 30° C. for 35 min until OD.sub.600 reaches approximately 0.4. Cool on an ice bath. Wash once with ultrapure water, wash twice with 10% glycerin, and finally resuspend with 10% glycerin; the amount of glyerin used is to produce a final concentration of the thalli concentrated by 500-1000 folds.

(58) {circle around (2)} Transformation by electric shock: Take out a 2-mm electrotransformation cup from 70% ethanol, wash with sterilized ultrapure water, and irradiate by UV lamp for 30 min. Precool at 4° C. for 30 min. Transfer 90 μL of finally resuspended cells to a precooled centrifuge tube, add 5 μL (more than 100 ng) of the full-length PCR segement (linear DNA) obtained in Step (1), suction gently by a gun, and maintain on an ice bath for 30 min. Electrotransformation Parameters: 2500V, 200Ω, 25 μF.

(59) {circle around (3)} Resuscitate and screen positive clones: add 1 mL of LB broth medium, and cultivate at 37° C. and 100 rpm for 1 h. Then smear one kanamycin (Kan) plate with every 200 μL, 5 plates in total. Smear evenly and allow to air-dry. Cultivate at 30° C. for 24 h. Pick up clones grown under kanamycin resistance, and carry out PCR identification to screen positive clones.

(60) No. of the obtained strain: AT-003-01 (AT-002-02, A nanA::fKanrf).

(61) (3) Removal of the Resistance Gene

(62) Introduce pCP20 into the above kanamycin-resistant clones, cultivate at 30° C. for 8 h, then increase to 42° C. and cultivate overnight, and thermally induce to express FLP recombinase; the plasmids are lost gradually. Streak the plate of antibiotics-free culture medium by an inoculating loop dipped in the bacterial suspension, pick up grown monoclones and dot on the kanamycin-resistant plate; those that cannot grown are clones of which the kanamycin resistance gene has been removed by FLP recombination. Carry out PCR with identification primer to identify clones losing kanamycin resistance.

(63) No. of the obtained strain: AT-003-02 (AT-002-02, Δ nanA).

(64) 3. Deletion of nagA Gene Sequence

(65) N-Acetyl-D-Glucosamine-6-Phosphate Deacetylase (NagA) can transform N-Acetyl-D-Glucosamine-6-Phosphate (GlcNAc-6-P) in microorganism into D-Glucosamine-6-Phosphate (GlcN-6-P). Deletion of the nagA gene sequence in nag operon (nagE-nagBACD) may blocktransformation of N-Acetyl-D-Glucosamine-6-Phosphate (GlcNAc-6-P) into D-Glucosamine-6-Phosphate (GlcN-6-P).

(66) (1) Preparation of Linear DNA Full-length PCR Segment for Targeting of Red Recombination

(67) Design of Homologous Arm Primers: From NCBI, look up NC_000913, nagA sequence SEQ ID No.10 for N-Acetyl-D-Glucosamine-6-Phosphate Deacetylase, Escherichia coli str. K-12, design the homologous arm primers for deletion of the nagA gene sequence: Forward primer (nagAKO-F) SEQ ID No.11 and reverse primer (nagAKO-R) SEQ ID No.12.

(68) Template: Amplification of fKanrf PCR Segment.

(69) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(70) Amplification Product: Homologous Arm+fKanf+Homologous Arm.

(71) The PCR product is separated by agarose gel electrophoresis, and purified and recovered to obtain 100 ng/μL linear DNA full-length PCR segment for targeting of Red recombination.

(72) (2) Red Recombination Operation

(73) First, pKD46 carrier is introduced into the AT-003-02 strain of Escherichia coli. Then, the prepared linear DNA segment for targeting is electrotransformed, and positive clones are screened. Finally, the resistance gene is removed.

(74) 1) Transformation of pKD46 Plasmid

(75) {circle around (1)} Preparation of Competence: First, inoculate the bacterial suspension of Escherichia coli AT-003-02 (AT-002-02, ΔnanA) stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h. then add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min. Finally, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(76) {circle around (2)} Plasmid Transformation: Transfer 250 μL of spontaneously sedimented thalli, add 5 μL of pKD46 plasmid, and cultivate at −4° C. for 30 min. Then heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h. Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate. Cultivate overnight (for 12-16 h) at 30° C. Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification. Store the positive strain for use.

(77) 2) Electrotransform linear DNA segment for targeting, and screen positive clone

(78) {circle around (1)} Preparation of Electrotransformed Competence: Inoculate the AT-003-02 strain of Escherichia coli, containing pKD46, into a test tube of LB medium containing Ampicillin (Amp), and shake-cultivate at 250 rpm, on the next day, inoculate in a ratio of 1% into LB medium containing Amp, and cultivate at 30° C.; when OD600 reaches approximately 0.2, add 0.2% L-Arabinose, and induce at 30° C. for 35 min until OD600 reaches approximately 0.4. Cool on an ice bath. Wash once with ultrapure water, wash twice with 10% glycerin, and finally resuspend with 10% glycerin; the amount of glyerin used is to produce a final concentration of the thalli concentrated by 500-1000 folds.

(79) {circle around (2)} Transformation by electric shock: Take out a 2-mm electrotransformation cup from 70% ethanol, wash with sterilized ultrapure water, and irradiate by UV lamp for 30 min. Precool at 4° C. for 30 min. Transfer 90 μL of finally resuspended cells to a precooled centrifuge tube, add 5 μL (more than 100 ng) of the full-length PCR segement (linear DNA) obtained in Step (1), suction gently by a gun, and maintain on an ice bath for 30 min. Electrotransformation Parameters: 2500V, 200Ω, 25 μF.

(80) {circle around (3)} Resuscitate and screen positive clones: add 1 mL of LB broth medium, and cultivate at 37° C. and 100 rpm for 1 h. Then smear one kanamycin (Kan) plate with every 200 μL, 5 plates in total. Smear evenly and allow to air-dry. Cultivate at 30° C. for 24 h. Pick up clones grown under kanamycin resistance, and carry out PCR identification to screen positive clones.

(81) No. of the obtained strain: AT-004-01 (AT-003-02, Δ nagA::fKanrf).

(82) (3) Removal of the Resistance Gene

(83) Introduce pCP20 into the above kanamycin-resistant clones, cultivate at 30° C. for 8 h, then increase to 42° C. and cultivate overnight, and thermally induce to express FLP recombinase; the plasmids are lost gradually. Streak the plate of antibiotics-free culture medium by an inoculating loop dipped in the bacterial suspension, pick up grown monoclones and dot on the kanamycin-resistant plate; those that cannot grown are clones of which the kanamycin resistance gene has been removed by FLP recombination. Carry out PCR with identification primer to identify clones losing kanamycin resistance.

(84) No. of the obtained strain: AT-004-02 (AT-003-02, Δ nagA).

(85) 4. Deletion of nagE Gene Sequence

(86) Deletion of the gene sequence nagE for N-Acetyl-D-Glucosamine Specific Enzyme II.sup.Nag (NagE) may block transport of extracellular GlcNAc into cells for degradation.

(87) (1) Preparation of Linear DNA Full-Length PCR Segment for Targeting of Red Recombination

(88) Design of Homologous Arm Primers: From NCBI, look up NC 000913, nagB promoter and nagA gene sequence SEQ ID No.13, Escherichia coli str. K-12, and design the homologous arm primers for deletion of the nagA gene sequence: Forward primer (nagEKO-F1) SEQ ID No.14 and reverse primer (nagEKO-R1) SEQ ID No.15.

(89) Template: Amplification of fKanrf PCR Segment.

(90) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(91) Amplification Product: Homologous Arm+fKanrf+Homologous Arm.

(92) The PCR product is separated by agarose gel electrophoresis, and purified and recovered to obtain 100 ng/μL linear DNA full-length PCR segment for targeting of Red recombination.

(93) (2) Red Recombination Operation

(94) First, pKD46 carrier is introduced into the AT-004-02 strain of Escherichia coli. Then, the prepared linear DNA segment for targeting is electrotransformed, and positive clones are screened. Finally, the resistance gene is removed.

(95) Transformation of pKD46 Plasmid

(96) {circle around (1)} Preparation of Competence: First, inoculate the bacterial suspension of Escherichia coli AT-004-02 (AT-003-02, Δ nagA) stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h. then add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min. Finally, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(97) {circle around (2)} Plasmid Transformation: Transfer 250 μL of spontaneously sedimented thalli, add 5 μL of pKD46 plasmid, and cultivate at −4° C. for 30 min. Then heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h. Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate. Cultivate overnight (for 12-16 h) at 30° C. Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification. Store the positive strain for use.

(98) 2) Electrotransform linear DNA segment for targeting, and screen positive clone

(99) {circle around (1)} Preparation of Electrotransformed Competence: Inoculate the AT-004-02 strain of Escherichia coli, containing pKD46, into a test tube of LB medium containing Ampicillin (Amp), and shake-cultivate at 250 rpm, on the next day, inoculate in a ratio of 1% into LB medium containing Amp, and cultivate at 30° C.; when OD600 reaches approximately 0.2, add 0.2% L-Arabinose, and induce at 30° C. for 35 min until OD600 reaches approximately 0.4. Cool on an ice bath. Wash once with ultrapure water, wash twice with 10% glycerin, and finally resuspend with 10% glycerin; the amount of glyerin used is to produce a final concentration of the thalli concentrated by 500-1000 folds.

(100) {circle around (2)} Transformation by electric shock: Take out a 2-mm electrotransformation cup from 70% ethanol, wash with sterilized ultrapure water, and irradiate by UV lamp for 30 min. Precool at 4° C. for 30 min. Transfer 90 μL of finally resuspended cells to a precooled centrifuge tube, add 5 μL (more than 100 ng) of the full-length PCR segement (linear DNA) obtained in Step (1), suction gently by a gun, and maintain on an ice bath for 30 min. Electrotransformation Parameters: 2500V, 200Ω, 25 μF.

(101) {circle around (3)} Resuscitate and screen positive clones: add 1 mL of LB broth medium, and cultivate at 37° C. and 100 rpm for 1 h. Then smear one kanamycin (Kan) plate with every 200 μL, 5 plates in total. Smear evenly and allow to air-dry. Cultivate at 30° C. for 24 h. Pick up clones grown under kanamycin resistance, and carry out PCR identification to screen positive clones.

(102) No. of the obtained strain: AT-005-01 (AT-004-02, Δ nagE::fKanrf).

(103) (3) Removal of the Resistance Gene

(104) Introduce pCP20 into the above kanamycin-resistant clones, cultivate at 30° C. for 8 h, then increase to 42° C. and cultivate overnight, and thermally induce to express FLP recombinase; the plasmids are lost gradually. Streak the plate of antibiotics-free culture medium by an inoculating loop dipped in the bacterial suspension, pick up grown monoclones and dot on the kanamycin-resistant plate; those that cannot grown are clones of which the kanamycin resistance gene has been removed by FLP recombination. Carry out PCR with identification primer to identify clones losing kanamycin resistance.

(105) No. of the obtained strain: AT-005-02 (AT-004-02, Δ nagE).

Example 2.a

(106) This example describes gene nanK cloning of N-Acetyl-D-Mannosamine Kinase (NanK), and transformed nanK/pTrc99A plasmids in Escherichia coli, as well as integration of ptrc-nanK gene cassette into the chromosome of Escherichia coli.

(107) 1. nanK Gene Cloning, Transformation of nanK/pTrc99A plasmid in Escherichia coli, and its Influence on the Output of N-Acetyl-D-Glucosamine

(108) Amplification of the gene nanK of Escherichia coli NanK (N-acetylmannosamine kinase, N-Acetyl-D-Mannosamine Kinase), that is controlled by Trc promoter to transform the strain for overexpression of the enzyme, may strengthen phosphorylation of ManNAc (N-Acetyl-D-mannosamine, N-Acetyl-D-Mannosamine or N-Acetyl-D-Mannosamine) into ManNAc-6-P (N-Acetyl-D-mannosamine-6-P, N-Acetyl-D-Mannosamine-6-Phosphate).

(109) 1) nanK Gene Cloning of Escherichia coli

(110) From NCBI, look up U00096, to obtain the nucleotide sequence SEQ ID No.16 of the nanK gene of Escherichia coli, which amino acid sequence is SEQ ID No.17.

(111) Primer Design: Forward primer (nanK-F) SEQ ID No.18 and reverse primer (nanK-R) SEQ ID No.19.

(112) Template: Escherichia coli AT-001.

(113) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(114) Amplification Product Size: 0.9 kb.

(115) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(116) Ligate the obtained PCR amplification segment with pUC57-T carrier, and carry out sequencing for identification, to obtain nanK/pUC57.

(117) 2) Construction and Transformation of Plasmid in which nanK gene is controlled by Trc promoter

(118) {circle around (1)} Plasmid Construction: Amplify plasmid nanK/pUC57, digest enzymatically nanK/pUC57 and carrier pTrc99A with Nco I and Hind III, separate by agarose gel electrophoresis, purify to recover nanK segment and pTrc99A segment, ligate overnight with T4 DNA ligase at 16° C., and carry out identification to obtain nanK/pTrc99A plasmid.

(119) {circle around (2)} Preparation of Competence: First, inoculate the bacterial suspension of AT-005-02 stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h. then add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min. Finally, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(120) {circle around (3)} Plasmid Transformation: Transfer 250 μL of spontaneously sedimented thalli, add 5 μL of nanK/pTrc99A plasmid, and cultivate at −4° C. for 30 min. Then heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h. Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate. Cultivate overnight (for 12-16 h) at 30° C. Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification. Store the positive strain for use. Obtain Recombinant Strain nanK/pTrc99A (AT-005-02)

(121) 3) Influence of nanK/pTrc99A plasmid transformation on the output of N-Acetyl-D-Glucosamine

(122) Carry out a shake-flask fermentation trial with the recombinant strain and nanK/pTrc99A (AT-005-02) reference strain. Transfer the monoclonal strain freshly cultivated in culture medium of the LB plate, inoculate into a test tube (13×150 mm) containing 3 mL of the LB broth culture medium, and shake-cultivate at 30° C. and 225 rpm for 8 h. Components of LB Broth Medium: 5 g/L yeast powder, 10 g/L peptone, and 10 g/L NaCl. Then transfer the seed culture solution, inoculate in 3% into a 250-mL shake-flask containing 50 mL of the fermentation culture solution (M9 culture solution). The initial OD.sub.600 is approximately 0.5; shake-cultivate at 37° C. and 225 rpm. The fermentation cycle is 72 h. At 24 h and 48 h, adjust to pH 7.0 with 10M NaOH. According to glucose consumption in the fermentation broth, add 65% glucose solution to maintain a glucose concentration of 20 g/L. After completion of fermentation, transfer 1 mL of the fermentation broth and centrifugate. Measure the content of N-Acetyl-D-Glucosamine by HPLC method.

(123) {circle around (1)} HPLC Method to Measure the Content of N-Acetyl-D-Glucosamine

(124) Buffer: Add 3.5 g of dipotassium hydrogen phosphate to 1-L volumetric flask, add water to dissolve, add 0.25 mL of ammonia water, then dilute with water and mix well, adjust to pH 7.5, and add wate to volume.

(125) Mobile Phase: Acetonitrile: Buffer (75:25).

(126) Diluent: Acetonitrile and water (50:50).

(127) Standard Solution: Dissolve 1.0 mg/Ml USP N-Acetyl-D-Glucosamine Reference Substance (RS) in the diluent.

(128) Sample Solution: Dissolve 1.0 mg/mL N-Acetyl-D-Glucosamine sample in the diluent.

(129) Liquid Phase Conditions: Model: LC

(130) Detector: UV 195 nm

(131) Chromatographic Column: 4.6-mm×15-cm; 3-μm packing L8 Flow Rate: 1.5 mL/min Column Temperature: 35° C.

(132) Injection Volume: 10 μL

(133) {circle around (2)} Preparation of M9 Culture Solution

(134) First prepare 5×M9 culture medium: To approximately 800 mL of double distilled water (ddH.sub.2O), add 64 g of Na.sub.2HPO.sub.4.Math.7H.sub.2O, 15 g of KH.sub.2PO.sub.4, 2.5 g of NaCl, and 5.0 g of NH.sub.4Cl, and after dissolution, add water to 1000 mL. Sterilize at 121° C. for 30 min. Then prepare 1M MgSO.sub.4, 1M CaCl.sub.2, and 20% glucose, respectively, and sterilize them separately. Then prepare M9 culture solution according to Table 1, while 1000× microelement solution is prepared according to Table 2.

(135) TABLE-US-00002 TABLE 1 Components of M9 Culture Solution Amount used Ingredients (mL/L) 5 × M9 200 1M MgSO.sub.4 2 1M CaCl.sub.2 0.1 20% Glucose 20 1000 × Microelement Solution 1 ddH.sub.2O to 1000 pH 6.9

(136) TABLE-US-00003 TABLE 2 Components of 1000 × Microelement Solution Amount used Ingredients (g/L) CoCl.sub.2•6H.sub.2O 0.01 CuSO.sub.4•5H.sub.2O 0.01 MnSO.sub.4•H.sub.2O 0.033 FeSO.sub.4•7H.sub.2O 0.50 ZnSO.sub.4•7H.sub.2O 0.38 H.sub.3BO.sub.3 0.01 NaMoO.sub.4•2H.sub.2O 0.01 pH 3

(137) {circle around (3)} Influence of nanK/pTrc99A plasmid transformation on the output of N-Acetyl-D-Glucosamine from shake-flask fermentation

(138) See Table 3 for the output from shake-flask fermentation. The results show that:

(139) The output by the reference strain AT-005-02 is very low and is not detected, while the output from overexpression by nanK gene of nanK/pTrc99A (AT-005-02), controlled by Trc promoter, is increased obviously.

(140) TABLE-US-00004 TABLE 3 Output from Shake-flask Fermentation by the Recombinant nanK/pTrc99A (AT-005-02) Output of N-Acetyl-D-Glucosamine species (g/L) AT-005-02 (AT-004-02, .sup.Δ nagE) (Reference) Not detected NanK/pTrc99A (AT-005-02) 2.9 ± 0.4

(141) 2. Integration of pTrc-nanK Gene Cassette into the Chromosome of Escherichia coli

(142) Using the nagE gene site as integration site of pTrc-nanK gene cassette into the chromosome. To achieve integration of pTrc-nanKgene cassette into the chromosome of Escherichia coli, first amplify the nanK segment (i.e. pTrc-nanK) with Trc promoter, as well as the kanamycin resistance gene segment with FLP recognition site (FRT site) at its both ends: FRT-Kanr-FRT (fKanrf), and splice them. Then design homologous primers for deletion of the nagE gene sequence, and using the spliced segment of pTrc-nanK and fKanrf as template, amplify the linear DNA full-length segment for targeting of Red recombination.

(143) The specific operating process is provided below:

(144) (1) PCR Amplification of pTrc-nanK Segment

(145) Template: nanK/pTrc99A.

(146) Primer Design: Forward primer (Trcff-F) SEQ ID No.20, and reverse primer (Trcff-R) SEQ ID No.21.

(147) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(148) Produce Size: 1.05 kb.

(149) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(150) (2) fKanrf Segment Amplified by PCR

(151) Primer Design: Forward primer (mfKanf-F) SEQ ID No.1, and reverse primer (mfKanf-R) SEQ ID No.2.

(152) Template: pPic9K.

(153) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(154) fKanrf size: 1.28 kb. Its nucleotide sequence is SEQ ID No.3.

(155) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(156) (3) Amplification of fKanrf Spliced with pTrc-nanK

(157) Primer Design: Forward primer (fKanf-F) SEQ ID No.22, and reverse primer (fKanf-R) SEQ ID No.23.

(158) Template: fKanrf.

(159) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(160) fKanrf size from secondary amplificatino: 1.3 kb.

(161) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(162) (4) Preparation of Linear DNA Full-Length PCR Segment for Targeting of Red Recombination

(163) Design of Homologous Arm Primers: Design again homologous arm primers for deletion of the nagE gene sequence: Forward primer (nagEKO-F2) SEQ ID No.24, and reverse primer (nagEKO-R2) SEQ ID No.25.

(164) Template: Mix pTrc-nanK PCR segment, and fKanrf PCR segment from secondary amplification in the ratio of 1:1.

(165) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(166) Amplification Product: Homologous Arm+pTrc-nanK-fKanrf+Homologous Arm

(167) The PCR product is separated by agarose gel electrophoresis, and purified and recovered to obtain 100 ng/μL linear DNA full-length PCR segment for targeting of Red recombination.

(168) (5) Red Recombination Operation

(169) First, pKD46 carrier is introduced into the AT-004-02 strain of Escherichia coli. Then, the prepared linear DNA segment for targeting is electrotransformed, and positive clones are screened. Finally, the resistance gene is removed.

(170) 1) Transformation of pKD46 Plasmid

(171) {circle around (1)} Preparation of Competence: First, inoculate the bacterial suspension of Escherichia coli AT-004-02 stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h. then add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min. Finally, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(172) {circle around (2)} Plasmid Transformation: Transfer 250 μL of spontaneously sedimented thalli, add 5 μL of pKD46 plasmid, and cultivate at −4° C. for 30 min. Then heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h. Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate. Cultivate overnight (for 12-16 h) at 30° C. Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification. Store the positive strain for use.

(173) 2) Electrotransform linear DNA segment for targeting, and screen positive clone

(174) {circle around (1)} Preparation of Electrotransformed Competence: Inoculate the AT-004-02 strain of Escherichia coli, containing pKD46, into a test tube of LB medium containing Ampicillin (Amp), and shake-cultivate at 250 rpm, on the next day, inoculate in a ratio of 1% into LB medium containing Amp, and cultivate at 30° C.; when OD600 reaches approximately 0.2, add 0.2% L-Arabinose, and induce at 30° C. for 35 min until OD600 reaches approximately 0.4. Cool on an ice bath. Wash once with ultrapure water, wash twice with 10% glycerin, and finally resuspend with 10% glycerin; the amount of glyerin used is to produce a final concentration of the thalli concentrated by 500-1000 folds.

(175) {circle around (2)} Transformation by electric shock: Take out a 2-mm electrotransformation cup from 70% ethanol, wash with sterilized ultrapure water, and irradiate by UV lamp for 30 min. Precool at 4° C. for 30 min. Transfer 90 μL of finally resuspended cells to a precooled centrifuge tube, add 5 μL (more than 100 ng) of the full-length PCR segement (linear DNA) obtained in Step (4), suction gently by a gun, and maintain on an ice bath for 30 min. Electrotransformation Parameters: 2500V, 200Ω, 25 μF.

(176) {circle around (3)} Resuscitate and screen positive clones: add 1 mL of LB broth medium, and cultivate at 37° C. and 100 rpm for 1 h. Then smear one kanamycin (Kan) plate with every 200 μL, 5 plates in total. Smear evenly and allow to air-dry. Cultivate at 30° C. for 24 h. Pick up clones grown under kanamycin resistance, and carry out PCR identification to screen positive clones.

(177) No. of the obtained strain: AT-006-01 (AT-004-02, Δ nagE::pTrc-nanK-fKanrf).

(178) (6) Removal of the Resistance Gene

(179) Introduce pCP20 into the above kanamycin-resistant clones, cultivate at 30° C. for 8 h, then increase to 42° C. and cultivate overnight, and thermally induce to express FLP recombinase; the plasmids are lost gradually. Streak the plate of antibiotics-free culture medium by an inoculating loop dipped in the bacterial suspension, pick up grown monoclones and dot on the kanamycin-resistant plate; those that cannot grown are clones of which the kanamycin resistance gene has been removed by FLP recombination. Carry out PCR with identification primer to identify clones losing kanamycin resistance.

(180) No. of the obtained strain: AT-006-02 (AT-004-02, Δ nagE::pTrc-nanK).

(181) 3. Influence of pTrc-nanK gene cassette integration on the output of N-Acetyl-D-Glucosamine

(182) Carry out a shake-flask fermentation trial with the recombinant strain AT-006-02 of which the nagE gene site in the chromosome is integrated with pTrc-nanK gene cassette, and the reference strain. Transfer the monoclonal strain freshly cultivated in culture medium of the LB plate, inoculate into a test tube (13×150 mm) containing 3 Ml of the LB broth culture medium, and shake-cultivate at 30° C. and 225 rpm for 8 h. Then transfer the seed culture solution, inoculate in 3% into a 250-Ml shake-flask containing 50 Ml of the fermentation culture solution (M9 culture solution). The initial OD600 is approximately 0.5; shake-cultivate at 37° C. and 225 rpm. The fermentation cycle is 72 h. At 24 h and 48 h, adjust to Ph 7.0 with 10M NaOH. According to glucose consumption in the fermentation broth, add 65% glucose solution to maintain a glucose concentration of 20 g/L. After completion of fermentation, transfer 1 Ml of the fermentation broth and centrifugate. Measure the content of N-Acetyl-D-Glucosamine by HPLC method.

(183) See Table 4 for the output from shake-flask fermentation. The results show that: The outputs by the reference strains AT-001 and AT-005-02 are very low and are not detected, while the output by the recombinant strain integrated with pTrc-nanK gene cassette is increased obviously, and is also increased significantly than that by the recombinant strain nanK/pTrc99A (AT-005-02) not integrated with the gene cassette.

(184) TABLE-US-00005 TABLE 4 Output from Shake-flask Fermentation by the Recombinant Strain integrated with pTrc-nanK Gene Cassette Output of N-Acetyl-D-Glucosamine Species (g/L) AT-001 (Reference) Not detected AT-005-02 (AT-004-02, .sup.Δ nagE) (Reference) Not detected nanK/pTrc99A (AT-005-02) 2.8 ± 0.5 AT-006-02 (AT-004-02, .sup.Δ nagE::pTrc-nanK) 4.2 ± 0.5

Example 2.b

(185) This implementation example describes screening for a gene mutant of N-Acetyl-D-MannosamineKinase (NanK); the said gene encodes N-Acetyl-D-Mannosamine Kinase (NanK) with increased activities.

(186) To further increase synthetic quantity of N-Acetyl-D-Glucosamine by the production strain, screen a gene mutant encoding N-Acetyl-D-Mannosamine Kinase (NanK) with increased activities. To achieve the purpose, amplify the cloned gene by error-prone PCR technology; used for amplified DNA polymerase, amplify the said gene under conditions leading to high-frequency mismatch, so as to obtain a high-frequency mutation in PCR products.

(187) The specific operating process is provided below:

(188) 2. Amplification of the Gene nanK of N-Acetyl-D-Mannosamine Kinase in Escherichia coli by Error-prone PCR

(189) By means of Taq DNA polymerase without the property of 3′-5′ proofreading function, control the frequency of random mutation under high magnesium ion concentration (8 mmol/L) and different Dntp concentrations (where, the concentration of Datp and Dgtp is 1.5 mmol/L; and the concentration of Dttp and Dctp is 3.0 mmol/L), introduce random mutations into the target gene, and construct a mutant library; the template concentration A260 value is 1000 ng/Ml, the enzyme concentration is 5 U/Ml, and the primer concentration is 100 Mm.

(190) Error-prone PCR reaction system (50 Ml): 10×PCR reaction buffer 5 μl, Dntp (2.5 Mm) 5 Ml, MgCl.sub.2 (25 Mm) 5 Ml, Forward primer (nanK-F, SEQ ID No.18) 1 Ml, reverse primer (nanK-R, SEQ ID No.19) 1 Ml, DNA template (nanK/Puc57) 0.1 Ml, Taq DNA polymerase 0.5 Ml, and ddH.sub.2O 32.4 Ml.

(191) PCR procedure: Predegenerate at 96° C. for 4 min; degenerate at 94° C. for 1 min, anneal at 56° C. for 1 min, extend at 75° C. for 2 min, and repeat for 45 cycles; finally extend at 75° C. for 15 min, recover PCR product (product size: 0.9 kb) by gel recovery method; transfer 5 Ml of the product and carry out 1% agarose gel electrophoresis test; the product is store at −20° C. for use.

(192) 2. Construction of the gene mutant library of N-Acetyl-D-Mannosamine Kinase

(193) Digest the above PCR product by two enzymes of restriction endonuclease Nco I and Hind III, carry out a ligation reaction with pTrc99A digested by Nco I and Hind III, then transform Escherichia coli AT-005-02 with the mixture of the ligated products to obtain a large amount of cloned transformants, and construct a mutant library of transformed thalli.

(194) 3. Screening for Mutants with High Enzyme Activities

(195) Using the wild type NanK/pTrc99A (AT-005-02) as reference, pick up randomly 300 mutant clones from the mutant library of transformed thalli, inoculate into 5 Ml of LB medium containing 50 μg/Ml Ampicillin (Amp), shake-cultivate at 37° C. and 150 rpm for 18 h, and then centrifugate at 10000 rpm for 5 mim and collect thalli. Discard the supernatant, then resuspend at 4° C. in 1 Ml of PBS solution (Ph 7.5, 10 mmol/L), carry out ultrasonicate at a voltage of 300 V for 10 min (ultrasonicate for 3 s and pause for 6 s), centrifugate, transfer the supernatant as crude extract of enzyme, and carry out a method for determination of enzyme activity.

(196) Determination of N-Acetyl-D-Mannosamine Kinase (NanK) Activity: Based on the phosphorylated amount of N-Acetyl-D-Mannosamine (ManNAc); that is to say, using the reduced amount of N-Acetyl-D-Mannosamine as test marker. Definition of Enzyme Activity Unit: Under the enzymatic reaction conditions, the enzyme amount reduced by the reducing sugar, equivalent to 1 μmol N-Acetyl-D-Mannosamine per minute, is defined as one enzyme activity unit (IU). The specific procedure is provided as follows: Transfer 5 mL of the reaction system as the system for determination of enzyme activity, which contains 500 mmol/L N-Acetyl-D-Mannosamine, 5 mmol/L glucose, 100 mmol/L Tris-HCl (pH8.0), and 100 μL of crude enzyme solution. Carry out the reaction for determination of enzyme activity on a water bath at 37° C., maintain for 4 h, and then place the enzymatic hydrolysate at 70° C. for 10 min to stop the reaction. Centrifugate at 3000 rpm for 10 min, and transfer the supernatant. Measure the content of N-Acetyl-D-Mannosamine by HPLC method.

(197) The results show that: The enzyme activity of the mutant strain with maximum activity is 77.5 IU/mL, and the enzyme activity of the reference control is 16.3 IU/mL. Transform NanK by error-prone PCR, to obtain a mutant strain with enzyme activity increased by 5 folds. Pick up the mutant strain with maximum enzyme activity and extract plasmids for sequencing. The results show that: The gene sequence of the mutant of N-Acetyl-D-Mannosamine Kinase is shown as SEQ ID No.26, and the corresponding amino acid is shown as SEQ ID No.27. By sequence alignment with the gene sequence of wild the type N-Acetyl-D-Mannosamine Kinase, 4 base point mutations occur in total: 107A/G, 309T/G, 669G/C, and 783A/G; There occur 3 missense mutations of amino acids, of which the mutation points are: Q36R (lysine at Site 36 is relaced by arginine), 1103M (isoleucine at Site 103 is replaced by methionine), and R223S (arginine at Site 223 is replaced by serine) The mutant gene is named as nanKM.

(198) 4. Integration of pTrc-nanK Gene Cassette into the nagE Gene Site in the Chromosome of Escherichia coli

(199) Using the nagE gene site as integration site of pTrc-nanKM gene cassette into the chromosome. To achieve integration of pTrc-nanKM gene cassette into the chromosome of Escherichia coli, first amplify the nanK segment (i.e. pTrc-nanKM) of Trc promoter, as well as the kanamycin resistance gene segment with FLP recognition site (FRT site) at its both ends: FRT-Kanr-FRT (fKanrf), and splice them. Then design homologous primers for deletion of the nagE gene sequence, and using the spliced segment of pTrc-nanKM and fKanrf as template, amplify the linear DNA full-length segment for targeting of Red recombination.

(200) The specific operating process is provided below:

(201) (1) PCR Amplification of pTrc-nanKM Segment

(202) Template: nanKM/pTrc99A.

(203) Primer Design: Forward primer (Trcff-F) SEQ ID No.20, and reverse primer (Trcff-R) SEQ ID No.21.

(204) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(205) Produce Size: 1.05 kb.

(206) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(207) (2) fKanrf segment amplified by PCR

(208) Primer Design: Forward primer (mfKanf-F) SEQ ID No.1, and reverse primer (mfKanf-R) SEQ ID No.2.

(209) Template: pPic9K.

(210) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(211) fKanrf size: 1.28 kb. Its nucleotide sequence is SEQ ID No.3.

(212) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(213) (3) Amplification of fKanrf spliced with pTrc-nanKM

(214) Primer Design: Forward primer (fKanf-F) SEQ ID No.22, and reverse primer (fKanf-R) SEQ ID No.23.

(215) Template: fKanrf.

(216) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(217) fKanrf size from secondary amplificatino: 1.3 kb.

(218) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(219) (4) Preparation of Linear DNA Full-length PCR Segment for Targeting of Red Recombination

(220) Design of Homologous Arm Primers: Design again homologous arm primers for deletion of the nagE gene sequence: Forward primer (nagEKO-F2) SEQ ID No.24, and reverse primer (nagEKO-R2) SEQ ID No.25.

(221) Template: Mix pTrc-nanKM PCR segment, and fKanrf PCR segment from secondary amplification in the ratio of 1:1.

(222) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(223) Amplification Product: Homologous Arm+pTrc-nanKM-fKanrf+Homologous Arm

(224) The PCR product is separated by agarose gel electrophoresis, and purified and recovered to obtain 100 ng/μL linear DNA full-length PCR segment for targeting of Red recombination.

(225) (5) Red Recombination Operation

(226) First, pKD46 carrier is introduced into the AT-004-02 strain of Escherichia coli. Then, the prepared linear DNA segment for targeting is electrotransformed, and positive clones are screened. Finally, the resistance gene is removed.

(227) 1) Transformation of pKD46 Plasmid

(228) {circle around (1)} Preparation of Competence: First, inoculate the bacterial suspension of Escherichia coli AT-004-02 stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h. Then add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min. Finally, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(229) {circle around (2)} Plasmid Transformation: Transfer 250 μL of spontaneously sedimented thalli, add 5 μL of pKD46 plasmid, and cultivate at −4° C. for 30 min. Then heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h. Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate. Cultivate overnight (for 12-16 h) at 30° C. Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification. Store the positive strain for use.

(230) 2) Electrotransform linear DNA segment for targeting, and screen positive clone

(231) {circle around (1)} Preparation of Electrotransformed Competence: Inoculate the AT-004-02 strain of Escherichia coli, containing pKD46, into a test tube of LB medium containing Ampicillin (Amp), and shake-cultivate at 250 rpm, on the next day, inoculate in a ratio of 1% into LB medium containing Amp, and cultivate at 30° C.; when OD600 reaches approximately 0.2, add 0.2% L-Arabinose, and induce at 30° C. for 35 min until OD600 reaches approximately 0.4. Cool on an ice bath. Wash once with ultrapure water, wash twice with 10% glycerin, and finally resuspend with 10% glycerin; the amount of glyerin used is to produce a final concentration of the thalli concentrated by 500-1000 folds.

(232) {circle around (2)} Transformation by electric shock: Take out a 2-mm electrotransformation cup from 70% ethanol, wash with sterilized ultrapure water, and irradiate by UV lamp for 30 min. Precool at 4° C. for 30 min. Transfer 90 μL of finally resuspended cells to a precooled centrifuge tube, add 5 μL (more than 100 ng) of the full-length PCR segement (linear DNA) obtained in Step (4), suction gently by a gun, and maintain on an ice bath for 30 min. Electrotransformation Parameters: 2500V, 200Ω, 25 μF.

(233) {circle around (3)} Resuscitate and screen positive clones: add 1 mL of LB broth medium, and cultivate at 37° C. and 100 rpm for 1 h. Then smear one kanamycin (Kan) plate with every 200 μL, 5 plates in total. Smear evenly and allow to air-dry. Cultivate at 30° C. for 24 h. Pick up clones grown under kanamycin resistance, and carry out PCR identification to screen positive clones.

(234) No. of the obtained strain: AT-007-01(AT-004-02, Δ nagE::pTrc-nanKM-fKanrf).

(235) (6) Removal of the Resistance Gene

(236) Introduce pCP20 into the above kanamycin-resistant clones, cultivate at 30° C. for 8 h, then increase to 42° C. and cultivate overnight, and thermally induce to express FLP recombinase; the plasmids are lost gradually. Streak the plate of antibiotics-free culture medium by an inoculating loop dipped in the bacterial suspension, pick up grown monoclones and dot on the kanamycin-resistant plate; those that cannot grown are clones of which the kanamycin resistance gene has been removed by FLP recombination. Carry out PCR with identification primer to identify clones losing kanamycin resistance.

(237) No. of the obtained strain: AT-007-02 (AT-004-02, Δ nagE::pTrc-nanKM).

(238) 5. Influence of pTrc-nanKM gene cassette integration on the output of N-Acetyl-D-Glucosamine

(239) Carry out a shake-flask fermentation trial with the recombinant strain AT-007-02 of which the nagE gene site in the chromosome is integrated with pTrc-nanKM gene cassette, and the reference strain. Transfer the monoclonal strain freshly cultivated in culture medium of the LB plate, inoculate into a test tube (13×150 mm) containing 3 mL of the LB broth culture medium, and shake-cultivate at 30° C. and 225 rpm for 8 h. Then transfer the seed culture solution, inoculate in 3% into a 250-mL shake-flask containing 50 mL of the fermentation culture solution (M9 culture solution). The initial OD600 is approximately 0.5; shake-cultivate at 37° C. and 225 rpm. The fermentation cycle is 72 h. At 24 h and 48 h, adjust to pH 7.0 with 10M NaOH. According to glucose consumption in the fermentation broth, add 65% glucose solution to maintain a glucose concentration of 20 g/L. After completion of fermentation, transfer 1 mL of the fermentation broth and centrifugate. Measure the content of N-Acetyl-D-Glucosamine by HPLC method.

(240) See Table 5 for the output from shake-flask fermentation. The results show that: The output by the reference strain AT-005-02 is very low and is not detected, while the output by the recombinant strain AT-007-02 integrated with pTrc-nanKM gene cassette is increased obviously, and is also increased significantly than that by the unmutant reference strain (AT-006-02).

(241) TABLE-US-00006 TABLE 5 Output from Shake-flask Fermentation by the Recombinant Strain integrated with pTrc-nanKM Gene Cassette Output of N-Acetyl-D-Glucosamine species (g/L) AT-005-02 (AT-004-02, .sup.Δ nagE) (Reference) Not detected AT-006-02 (AT-004-02, .sup.Δ nagE::pTrc-nanK)  4.5 ± 0.4 AT-007-02 (AT-004-02, .sup.Δ nagE::pTrc-NanKM) 11.2 ± 1.2

(242) The above results show that: The output of N-Acetyl-D-Glucosamine may be increased obviously by overexpression of N-Acetyl-D-Mannosamine Kinase; moreover, the output of N-Acetyl-D-Glucosamine may also be greatly by the mutant screened by error-prone PCR technology, due to increased activities of the obtained mutant of the enzyme.

Example 2.c

(243) This implementation example describes Escherichia coli strains integrated with pTrc-nanKM gene cassette, and the gene vhb thereof and its mutant for expression of vitreoscilla hemoglobin (Vhb) as well as influence on the output of N-Acetyl-D-Glucosamine.

(244) Amplify the gene vhb for vitreoscilla hemoglobin (Vhb), insert into pTrc99A, so that vhb is controlled by Trc promoter to transform the strains, or screen a mutant of the gene vhb for vitreoscilla hemoglobin (Vhb) and insert into pTrc99A to transform the strains, to increase the microorganism's utilization ability for dissolved oxygen and increase the fermentation production the output of N-Acetyl-Glucosamine.

(245) 1. Escherichia coli strains integrated with pTrc-nanKM gene cassette, and the gene vhb for expression of vitreoscilla hemoglobin (Vhb)

(246) (1) Amplify the vhb Gene and Insert into pTrc99A

(247) The nucleotide sequence the gene encoding vitreoscilla hemoglobin (Vhb) is SEQ ID No.60, and the amino acid sequence is SEQ ID No.61. Based on the preference cocon bases of Escherichia coli, optimize and synthesize the gene for vitreoscilla hemoglobin (Vhb), and load into pUC57 carrier. Obtain a carrier named as: pVS/pUC57.

(248) Primer Design: Forward primer (vhb-F) SEQ ID No.62, and reverse primer (vhb-R) SEQ ID No.63.

(249) Template: pVS/pUC57.

(250) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(251) Amplification Product Size: 441 bp.

(252) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(253) Digest enzymatically the obtained PCR amplification segment and carrier pTrc99A with Nco I and Hind III, separate by agarose gel electrophoresis, purify and recover vhb segment and pTrc99A segment, ligate overnight with T4 DNA ligase at 16° C., and carry out identification to obtain vhb/pTrc99A plasmid.

(254) (2) Transform Escherichia coli strains integrated with pTrc-NanKM gene gassette by vhb/pTrc99A

(255) 1) Preparation of Competence

(256) {circle around (1)} Inoculate the bacterial suspension of AT-007-02 stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h.

(257) {circle around (2)} Add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min.

(258) {circle around (3)} Centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(259) 2) Plasmid Transformation

(260) {circle around (1)} Transfer 250 μL of spontaneously sedimentated thalli, add 5 μL of vhb/pTrc99A plasmid, and cultivate at −4° C. for 30 min.

(261) {circle around (2)} Heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h.

(262) {circle around (3)} Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate.

(263) {circle around (4)} Cultivate overnight (for 12-16 h) at 30° C.

(264) {circle around (5)} Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification.

(265) {circle around (6)} Positive clones are stored for use.

(266) No. of the obtained strain: AT-052 (AT-007-02, vhb/pTrc99A).

(267) 2. Escherichia coli strains integrated with pTrc-nanKM gene cassette, and the gene vhb mutant for expression of vitreoscilla hemoglobin (Vhb)

(268) To further increase synthetic quantity of N-Acetyl-D-Glucosamine by the production strain, screen a gene mutant encoding vitreoscilla hemoglobin (Vhb) with increased activities. To achieve the purpose, amplify the cloned gene by error-prone PCR technology; used for amplified DNA polymerase, amplify the said gene under conditions leading to high-frequency mismatch, so as to obtain a high-frequency mutation in PCR products.

(269) The specific operating process is provided below:

(270) (1) Error-prone PCR amplification of the gene vhb for vitreoscilla hemoglobin (Vhb) in Escherichia coli

(271) By means of Taq DNA polymerase without the property of 3′-5′ proofreading function, control the frequency of random mutation under high magnesium ion concentration (8 mmol/L) and different dNTP concentrations (where, the concentration of dATP and dGTP is 1.5 mmol/L; and the concentration of dTTP and dCTP is 3.0 mmol/L), introduce random mutations into the target gene, and construct a mutant library; the template concentration A260 value is 1000 ng/mL, the enzyme concentration is 5 U/μL, and the primer concentration is 100 μM.

(272) Error-prone PCR reaction system (50 μL): 10×PCR reaction buffer 5 μl, dNTP (2.5 mM) 5 μL, MgCl.sub.2 (25 mM) 5 μL, Forward primer (vhb-F, SEQ ID No.62) 1 μL, reverse primer (vhb-R, SEQ ID No.63) 1 μL, DNA template (nanK/pUC57) 0.1 μL, Taq DNA polymerase 0.5 μL, and ddH.sub.2O 32.4 μL.

(273) PCR procedure: Predegenerate at 96° C. for 4 min; degenerate at 94° C. for 1 min, anneal at 56° C. for 1 min, extend at 75° C. for 2 min, and repeat for 45 cycles; finally extend at 75° C. for 15 min, recover PCR product (product size: 0.44 kb) by gel recovery method; transfer 5 μL of the product and carry out 1% agarose gel electrophoresis test; the product is store at −20° C. for use.

(274) (2) Construction of the gene mutant library for vitreoscilla hemoglobin (Vhb) Digest the above PCR product by two enzymes of restriction endonuclease Nco I and Hind III, carry out a ligation reaction with pTrc99A digested by Nco I and Hind III, then transform Escherichia coli AT-005-02 with the mixture of the ligated products to obtain a large amount of cloned transformants, and construct a mutant library of transformed thalli.

(275) (3) Screening for mutants with higher activities

(276) Using the wild type vhb/pTrc99A (AT-005-02) as reference, pick up randomly 420 mutant clones from the mutant library of transformed thalli, inoculate into 5 mL of LB medium containing 50 μg/mL Ampicillin (Amp), shake-cultivate at 37° C. and 150 rpm for 18 h, and then centrifugate at 10000 rpm for 5 min and collect thalli. Discard the supernatant, then resuspend at 4° C. in 1 mL of PBS solution (pH 7.5, 10 mmol/L), carry out ultrasonicate at a voltage of 300 V for 10 min (ultrasonicate for 3 s and pause for 6 s), centrifugate, transfer the supernatant as crude extract, and carry out a method for determination of activity.

(277) Determination of vitreoscilla hemoglobin activities: Carry out the 1 CO-differential chromatography for determination of vitreoscilla hemoglobin activities. As the conjugate of CO and vitreoscilla hemoglobin may produce a strong absorption peak at the wavelength of 420 nm, and form a typical characteristic curve of Vhb, so the activities of Vhb may be reflected by test results of the absorption peak intensity. Test Method: Based on the feed-batch fermentation trial of different batches of the above different types of recombinant Escherichia coli under limited oxygen cultivation and low oxygen (dissolved oxygen <=20%) conditions, transfer 6 mL each of the culture solution, and centrifugate and collect thalli. Wash the precipitate once with saline solution (100 mmol/L Tris-HCl, 50 mmol/L NaCl, pH7.5), then resuspend in 3 mL of the buffer, ultrasonicate, and centrifugate at 4° C. and 10 000 rpm for 15 min. Transfer the supernatant, dilute by 2 folds with 3 mL of the buffer, and add Sodium Hydrosulfite (Na2S2O4) to a final concentration of 2.5 mg/mL, and then introduce CO gas into the solution. After 3 min later, scan by the ultraviolet-visible spectrometer at the wave band of 400-500 nm, and determine vitreoscilla hemoglobin activities from the maximum absorption peak (Abs) of the ultraviolet spectrum.

(278) Screen to obtain one mutant strain with the maximum activities. Pick up the strain and extract plasmid, and carry out sequencing. The results show that: The mutant gene sequence of vitreoscilla hemoglobin is shown as SEQ ID No.64, and the corresponding amino acid sequence is shown as SEQ ID No.65. By sequence alignment with the gene sequence of the wild type N-Acetyl-D-Mannosamine Kinase, 3 base point mutations occur in total: 133A/C, 256T/G, and 284A/C. There occur 3 missense mutations of amino acids, of which the mutation points are: M45L (methionine at Site 45 is replaced by leucine), C86G (cysteine at Site 86 is replaced by glycine), and Y95S (tyrosine at Site 95 is replaced by serine). The mutant gene is named as vhbM.

(279) (4) Transform Escherichia coli strains integrated with pTrc-NanKM gene gassette by vhbM/pTrc99A

(280) 1) Preparation of Competence

(281) {circle around (1)} Inoculate the bacterial suspension of AT-007-02 stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h.

(282) {circle around (2)} Add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min.

(283) {circle around (3)} Centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(284) 2) Plasmid Transformation

(285) {circle around (1)} Transfer 250 μL of spontaneously sedimentated thalli, add 5 μL of vhbM/pTrc99A plasmid, and cultivate at −4° C. for 30 min.

(286) {circle around (2)} Heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h.

(287) {circle around (3)} Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate.

(288) {circle around (4)} Cultivate overnight (for 12-16 h) at 30° C.

(289) {circle around (5)} Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification.

(290) {circle around (6)} Positive clones are stored for use.

(291) No. of the obtained strain: AT-053 (AT-007-02, vhbM/pTrc99A).

(292) 2. Escherichia coli strains integrated with pTrc-nanKM gene cassette, and the gene vhb thereof and its mutants for expression of vitreoscilla hemoglobin (Vhb) as well as influence on the output of N-Acetyl-D-Glucosamine

(293) Carry out a shake-flask fermentation trial with the strains integrated with pTrc-nanKM gene cassette, and the mutant strains AT-052 and AT-053 with the gene vhb for expression of vitreoscilla hemoglobin (Vhb). Transfer the monoclonal strain freshly cultivated in culture medium of the LB plate, inoculate into a test tube (13×150 mm) containing 3 mL of the LB broth culture medium, and shake-cultivate at 30° C. and 225 rpm for 8 h. Then transfer the seed culture solution, inoculate in 3% into a 250-mL shake-flask containing 50 mL of M9 culture solution. The initial OD.sub.600 is approximately 0.5; shake-cultivate at 37° C. and 225 rpm. The fermentation cycle is 72 h. At 24 h and 48 h, adjust to pH 7.0 with 10M NaOH. According to glucose consumption in the fermentation broth, add 65% glucose solution to maintain a glucose concentration of 20 g/L. After completion of fermentation, transfer 1 mL of the fermentation broth and centrifugate. Measure the content of N-Acetyl-D-Glucosamine by HPLC method.

(294) See Table 6 for the output from shake-flask fermentation by recombinant strains. The results show that: The output may be increased obviously from expression of vhb by the recombinant strains both with transformed vhb/pTrc99A and with transformed vhbM/pTrc99A plasmid; moreover, the output is increased more significant by the recombinant strain with transformed vhbM/pTrc99A plasmid.

(295) TABLE-US-00007 TABLE 6 Output from Shake-flask Fermentation by the Recombinant Strains for Expression of vhb and vhbM Output of N-Acetyl-D-Glucosamine Species (g/L) AT-007-02 (Reference) 11.4 ± 1.2 AT-052 (AT-007-02, vhb/pTrc99A) 16.5 ± 1.1 AT-053 (AT-007-02, vhbM/pTrc99A) 20.7 ± 1.5

Example 3.a

(296) This example describes gene nanE cloning of N-Acetyl-D-Mannosamine-6-P Epimerase (NanE), and transformed nanK/pTrc99A plasmids in Escherichia coli, as well as integration of ptrc-nanE gene cassette into the chromosome of Escherichia coli.

(297) 1. nanE Gene Cloning, Transformation of nanE/pTrc99A plasmid in Escherichia coli, and its Influence on the Output of N-Acetyl-D-Glucosamine

(298) Amplify the gene nanE of Escherichia coli NanE (N-Acetyl-D-Mannosamine-6-P Epimerase), insert into pTrc so that nanE is controlled by Trc promoter to transform the strains for overexpression, to strengthen transformation of N-Acetyl-D-Mannosamine-6-Phosphate (ManNAc-6-P) into N-Acetyl-D-Glucosamine-6-Phosphate (GlcNAc-6-P).

(299) 1) nanE Gene Cloning of Escherichia coli

(300) From NCBI, look up U00096, to obtain the nucleotide sequence SEQ ID No.28 of the nanE gene of Escherichia coli, which amino acid sequence is SEQ ID No.29.

(301) Primer Design: Forward primer (nanE-F) SEQ ID No.30, and reverse primer (nanE-R) SEQ ID No.31.

(302) Template: AT-001 (Escherichia coli ATCC 27325) Genome.

(303) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3 Extend at 72° C. for 10 min.

(304) Amplification Product Size: 690 kb.

(305) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(306) Ligate the obtained PCR amplification segment with pUC57-T carrier, and carry out sequencing for identification to obtain nanE/pUC57.

(307) 2) Construction and Transformation of Plasmid in which nanE gene is controlled by Trc promoter

(308) {circle around (1)} Plasmid Construction: Amplify plasmid nanE/pUC57, digest enzymatically nanE/pUC57 and carrier pTrc99A with Nco I and Hind III, separate by agarose gel electrophoresis, purify to recover nanE segment and pTrc99A segment, ligate overnight with T4 DNA ligase at 16° C., and carry out identification to obtain nanE/pTrc99A plasmid.

(309) {circle around (2)} Preparation of Competence: First, inoculate the bacterial suspension of AT-005-02 stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h. then add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min. Finally, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(310) {circle around (3)} Plasmid Transformation: Transfer 250 μL of spontaneously sedimented thalli, add 5 μL of nanE/pTrc99A plasmid, and cultivate at −4° C. for 30 min. Then heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h. Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate. Cultivate overnight (for 12-16 h) at 30° C. Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification. Store the positive strain for use. Obtain Recombinant Strain nanE/pTrc99A (AT-005-02)

(311) 3) Influence of nanE/pTrc99A plasmid transformation on the output of N-Acetyl-D-Glucosamine

(312) Carry out a shake-flask fermentation trial with the recombinant strain nanE/pTrc99A (AT-005-02) and the reference strain. Transfer the monoclonal strain freshly cultivated in culture medium of the LB plate, inoculate into a test tube (13×150 mm) containing 3 mL of the LB broth culture medium, and shake-cultivate at 30° C. and 225 rpm for 8 h. Components of LB Broth Medium: 5 g/L yeast powder, 10 g/L peptone, and 10 g/L NaCl. Then transfer the seed culture solution, inoculate in 3% into a 250-mL shake-flask containing 50 mL of the fermentation culture solution (M9 culture solution). The initial OD.sub.600 is approximately 0.5; shake-cultivate at 37° C. and 225 rpm. The fermentation cycle is 72 h. At 24 h and 48 h, adjust to pH 7.0 with 10M NaOH. According to glucose consumption in the fermentation broth, add 65% glucose solution to maintain a glucose concentration of 20 g/L. After completion of fermentation, transfer 1 mL of the fermentation broth and centrifugate. Measure the content of N-Acetyl-D-Glucosamine by HPLC method.

(313) See Table 7 for the output from shake-flask fermentation. The results show that: The output by the reference strain AT-005-02 is very low and is not detected, while the output from overexpression by nanE gene of nanE/pTrc99A (AT-005-02), controlled by Trc promoter, is increased obviously.

(314) TABLE-US-00008 TABLE 7 Output from Shake-flask Fermentation by the Recombinant Strain nanE/pTrc99A (AT-005-02) Output of N-Acetyl-D-Glucosamine species (g/L) AT-005-02 (AT-004-02, .sup.Δ nagE) (Reference) Not detected nanE/pTrc99A (AT-005-02) 1.4 ± 0.4

(315) 2. Integration of pTrc-nanE Gene Cassette into the Chromosome of Escherichia coli

(316) Using the nagE gene site as integration site of pTrc-nanE gene cassette into the chromosome. To achieve integration of pTrc-nanE gene cassette into the chromosome of Escherichia coli, first amplify the nanE segment (i.e. pTrc-nanE) with Trc promoter, as well as the kanamycin resistance gene segment with FLP recognition site (FRT site) at its both ends: FRT-Kanr-FRT (fKanrf), and splice them. Then design homologous primers for deletion of the nagE gene sequence, and using the spliced segment of pTrc-nanE and fKanrf as template, amplify the linear DNA full-length segment for targeting of Red recombination.

(317) The specific operating process is provided below:

(318) (1) PCR Amplification of pTrc-nanE Segment

(319) Template: nanE/pTrc99A.

(320) Primer Design: Forward primer (Trcff-F) SEQ ID No.20, and reverse primer (Trcff-R) SEQ ID No.21.

(321) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(322) Product Size: 0.86 kb.

(323) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(324) (2) fKanrf segment amplified by PCR

(325) Primer Design: Forward primer (mfKanf-F) SEQ ID No.1, and reverse primer (mfKanf-R) SEQ ID No.2.

(326) Template: pPic9K.

(327) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(328) fKanrf size: 1.28 kb. Its nucleotide sequence is SEQ ID No.3.

(329) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(330) (3) Amplification of fKanrf spliced with pTrc-nanE

(331) Primer Design: Forward primer (fKanf-F) SEQ ID No.22, and reverse primer (fKanf-R) SEQ ID No.23.

(332) Template: fKanrf.

(333) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(334) fKanrf size from secondary amplificatino: 1.3 kb.

(335) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(336) (4) Preparation of Linear DNA Full-length PCR Segment for Targeting of Red Recombination

(337) Design of Homologous Arm Primers: Design again homologous arm primers for deletion of the nagE gene sequence: Forward primer (nagEKO-F2) SEQ ID No.24, and reverse primer (nagEKO-R2) SEQ ID No.25.

(338) Template: Mix pTrc-nanE PCR segment, and fKanrf PCR segment from secondary amplification in the ratio of 1:1.

(339) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(340) Amplification Product: Homologous Arm+pTrc-nanE-fKanrf+Homologous Arm

(341) The PCR product is separated by agarose gel electrophoresis, and purified and recovered to obtain 100 ng/μL linear DNA full-length PCR segment for targeting of Red recombination.

(342) (5) Red Recombination Operation

(343) First, pKD46 carrier is introduced into the AT-004-02 strain of Escherichia coli. Then, the prepared linear DNA segment for targeting is electrotransformed, and positive clones are screened. Finally, the resistance gene is removed.

(344) 1) Transformation of pKD46 Plasmid

(345) {circle around (1)} Preparation of Competence: First, inoculate the bacterial suspension of Escherichia coli AT-004-02 stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h. then add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min. Finally, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(346) {circle around (2)} Plasmid Transformation: Transfer 250 μL of spontaneously sedimented thalli, add 5 μL of pKD46 plasmid, and cultivate at −4° C. for 30 min. Then heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h. Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate. Cultivate overnight (for 12-16 h) at 30° C. Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification. Store the positive strain for use.

(347) 2.) Electrotransform linear DNA segment for targeting, and screen positive clone

(348) {circle around (1)} Preparation of Electrotransformed Competence: Inoculate the AT-004-02 strain of Escherichia coli, containing pKD46, into a test tube of LB medium containing Ampicillin (Amp), and shake-cultivate at 250 rpm, on the next day, inoculate in a ratio of 1% into LB medium containing Amp, and cultivate at 30° C.; when OD600 reaches approximately 0.2, add 0.2% L-Arabinose, and induce at 30° C. for 35 min until OD600 reaches approximately 0.4. Cool on an ice bath. Wash once with ultrapure water, wash twice with 10% glycerin, and finally resuspend with 10% glycerin; the amount of glyerin used is to produce a final concentration of the thalli concentrated by 500-1000 folds.

(349) {circle around (2)} Transformation by electric shock: Take out a 2-mm electrotransformation cup from 70% ethanol, wash with sterilized ultrapure water, and irradiate by UV lamp for 30 min. Precool at 4° C. for 30 min. Transfer 90 μL of finally resuspended cells to a precooled centrifuge tube, add 5 μL (more than 100 ng) of the full-length PCR segement (linear DNA) obtained in Step (4), suction gently by a gun, and maintain on an ice bath for 30 min. Electrotransformation Parameters: 2500V, 200Ω, 25 μF.

(350) {circle around (3)} Resuscitate and screen positive clones: add 1 mL of LB broth medium, and cultivate at 37° C. and 100 rpm for 1 h. Then smear one kanamycin (Kan) plate with every 200 μL, 5 plates in total. Smear evenly and allow to air-dry. Cultivate at 30° C. for 24 h. Pick up clones grown under kanamycin resistance, and carry out PCR identification to screen positive clones.

(351) No. of the obtained strain: AT-030-01 (AT-004-02, Δ nagE::pTrc-nanE-fKanrf).

(352) (6) Removal of the Resistance Gene

(353) Introduce pCP20 into the above kanamycin-resistant clones, cultivate at 30° C. for 8 h, then increase to 42° C. and cultivate overnight, and thermally induce to express FLP recombinase; the plasmids are lost gradually. Streak the plate of antibiotics-free culture medium by an inoculating loop dipped in the bacterial suspension, pick up grown monoclones and dot on the kanamycin-resistant plate; those that cannot grown are clones of which the kanamycin resistance gene has been removed by FLP recombination. Carry out PCR with identification primer to identify clones losing kanamycin resistance.

(354) No. of the obtained strain: AT-030-02 (AT-004-02, Δ nagE::pTrc-nanE).

(355) 3. Influence of the integration of pTrc-nanE gene cassette on the output of N-Acetyl-D-Glucosamine

(356) Carry out a shake-flask fermentation trial with the recombinant strain AT-030-02 of which the nagE gene site in the chromosome is integrated with pTrc-nanE gene cassette, and the reference strain. Transfer the monoclonal strain freshly cultivated in culture medium of the LB plate, inoculate into a test tube (13×150 mm) containing 3 mL of the LB broth culture medium, and shake-cultivate at 30° C. and 225 rpm for 8 h. Then transfer the seed culture solution, inoculate in 3% into a 250-mL shake-flask containing 50 mL of the fermentation culture solution (M9 culture solution). The initial OD.sub.600 is approximately 0.5; shake-cultivate at 37° C. and 225 rpm. The fermentation cycle is 72 h. At 24 h and 48 h, adjust to pH 7.0 with 10M NaOH. According to glucose consumption in the fermentation broth, add 65% glucose solution to maintain a glucose concentration of 20 g/L. After completion of fermentation, transfer 1 mL of the fermentation broth and centrifugate. Measure the content of N-Acetyl-D-Glucosamine by HPLC method.

(357) See Table 8 for the output from shake-flask fermentation. The results show that: The outputs by the reference strains AT-001 and AT-005-02 are very low and are not detected, while the output by the recombinant strain integrated with pTrc-nanE gene cassette is increased obviously, and is also increased significantly than that by the recombinant strain nanE/pTrc99A (AT-005-02) not integrated with the gene cassette.

(358) TABLE-US-00009 TABLE 8 Output from Shake-flask Fermentation by the Recombinant Strain integrated with pTrc-nanE Gene Cassette Output of N-Acetyl-D-Glucosamine Species (g/L) AT-001 (Reference) Not detected AT-005-02 (AT-004-02, .sup.Δ nagE) (Reference) Not detected nanE/pTrc99A (AT-005-02) 1.2 ± 0.3 AT-030-02 (AT-004-02, .sup.Δ nagE::pTrc-nanE) 2.5 ± 0.5

Example 3.b

(359) This implementation example describes screening for a gene mutant of N-Acetyl-D-Mannosamine-6-P Epimerase (NanE); the said gene encodes N-Acetyl-D-Mannosamine-6-P Epimerase (NanE) with increased activities.

(360) To further increase synthetic quantity of N-Acetyl-D-Glucosamine by the production strain, screen a gene mutant encoding N-Acetyl-D-Mannosamine-6-P Epimerase with increased activities. To achieve the purpose, amplify the cloned gene by error-prone PCR technology; used for amplified DNA polymerase, amplify the said gene under conditions leading to high-frequency mismatch, so as to obtain a high-frequency mutation in PCR products.

(361) The specific operating process is provided below:

(362) 1. Amplification of the Gene nanE of N-Acetyl-D-Mannosamine-6-P Epimerase in Escherichia coli by Error-prone PCR

(363) By means of Taq DNA polymerase without the property of 3′-5′ proofreading function, control the frequency of random mutation under high magnesium ion concentration (8 mmol/L) and different dNTP concentrations (where, the concentration of dATP and dGTP is 1.5 mmol/L; and the concentration of dTTP and dCTP is 3.0 mmol/L), introduce random mutations into the target gene, and construct a mutant library; the template concentration A260 value is 1000 ng/mL, the enzyme concentration is 5 U/μL, and the primer concentration is 100 μM.

(364) Error-prone PCR reaction system (50 μL): 10×PCR reaction buffer 5 μl, dNTP (2.5 mM) 5 μL, MgCl.sub.2 (2.5 mM) 5 μL, Forward primer (nanE-F, SEQ ID No.30) 1 μL, reverse primer (nanE-R, SEQ ID No.31) 1 μL, DNA template (nanE/pUC57) 0.1 μL, Taq DNA polymerase 0.5 μL, and ddH.sub.2O 32.4 μL.

(365) PCR procedure: Predegenerate at 96° C. for 4 min; degenerate at 94° C. for 1 min, anneal at 56° C. for 1 min, extend at 75° C. for 2 min, and repeat for 45 cycles; finally extend at 75° C. for 15 min, recover PCR product (product size: 0.7 kb) by gel recovery method; transfer 5 μL of the product and carry out 1% agarose gel electrophoresis test; the product is store at −20° C. for use.

(366) 2. Construction of the gene mutant library of N-Acetyl-D-Mannosamine-6-P Epimerase

(367) Digest the above PCR product by two enzymes of restriction endonuclease Nco I and Hind III, carry out a ligation reaction with pTrc99A digested by Nco I and Hind III, then transform Escherichia coli AT-005-02 with the mixture of the ligated products to obtain a large amount of cloned transformants, and construct a mutant library of transformed thalli.

(368) 3. Screening for Mutants with High Enzyme Activities

(369) Using the wild type NanE/pTrc99A (AT-005-02) as reference, pick up randomly 350 mutant clones from the mutant library of transformed thalli, inoculate into 5 m of LB medium containing 50 μg/mL Ampicillin (Amp), shake-cultivate at 37° C. and 150 rpm for 18 h, and then centrifugate at 10000 rpm for 5 mim and collect thalli. Discard the supernatant, then resuspend at 4° C. in 1 mL of PBS solution (pH 7.5, 10 mmol/L), carry out ultrasonicate at a voltage of 300 V for 10 min (ultrasonicate for 3 s and pause for 6 s), centrifugate, transfer the supernatant as crude extract of enzyme, and carry out a method for determination of enzyme activity.

(370) Determination of N-Acetyl-D-Mannosamine-6-P Epimerase Activity: Based on the amount of N-Acetyl-D-Mannosamine-6-Phosphate (ManNAc-6-P) transformed into N-Acetyl-D-Glucosamine-6-Phosphate (GlcNAc-6-P); that is to say, using the reduced amount of N-Acetyl-D-Mannosamine-6-Phosphate as test marker. Definition of Enzyme Activity Unit: Under the enzymatic reaction conditions, the enzyme amount reduced, equivalent to 1 μmol N-Acetyl-D-Mannosamine-6-Phosphate per minute, is defined as one enzyme activity unit (IU). The specific procedure is provided as follows: First, prepare isotope-labelled ManNAc-6-P as substrate. Prepare a reaction solution in a total volume of 225 uL, containing ManNAc Kinase (NanK) crude solution (containing 1-5 mg protein), 20 mM ATP disodium, 60 mM Tris-HCl, pH8.1, 20 mM MgCl.sub.2, 5 mM ManNAc, and 50 nCi [.sup.14C]ManNAc. Incubate at 37° C. for 30 min. Add 350 uL of alcohol to stop the reaction. The product is eluted and lyophilized with water. Secondly, prepare a reaction solution in a total volume of 26.5 uL as the determination system for enzyme activity, containing 1 mM isotope-labelled ManNAc-6-P, 37 mM Tris-HCl, pH 8.0, and 19 mM MgCl.sub.2. Incubate at 37° C. for 30 min, heat the reaction solution to boil for 3 min, then add 0.1 volume of alkaline phosphatase buffer to adjust pH and 20 U of alkaline phosphatase. Incubate at 37° C. for 1 h, draw a sample and add on a dry chromatography paper, and presoak with 1% sodium tetraborate. The used solvent system is a mixture of ethyl acetate:isopropanol:pyridine:water (50:22:14:14). Separate radioactive compounds by paper chromatography. Measure the radioactive intensity by a liquid scintillation counter, and calculate the activity units of N-Acetyl-D-Mannosamine-6-P Epimerase, based on the amount of ManNAc-6-P transformed into GlcNAc-6-P.

(371) The results show that: The enzyme activity of the mutant strain with maximum activity is 72 IU/mL, and the enzyme activity of the reference control is 9.5 IU/mL. Transform NanE by error-prone PCR, to obtain a mutant strain with enzyme activity increased greatly. Pick up the mutant strain with maximum enzyme activity and extract plasmids for sequencing. The results show that: The mutant gene sequence of N-Acetyl-D-Mannosamine-6-P Epimerase is shown as SEQ ID No.56, and the corresponding amino acid sequence is shown as SEQ ID No.57. Through gene sequence alignment with the wild type of N-Acetyl-D-Mannosamine-6-P Epimerase, 3 base point mutations occur in total: 198C/T, 397T/C, and 559T/C. There occur 2 missense mutations of amino acids, of which the mutation points are: Q133R (cysteine at Site 133 is replaced by arginine), and Y187H (tyrosine at Site 187 is replaced by histidine). The mutant gene is named as nanEM.

(372) 4. Integration of pTrc-nanEM Gene Cassette into the nagE Gene Site in the Chromosome of Escherichia coli

(373) Using the nagE gene site as integration site of pTrc-nanEM gene cassette into the chromosome. To achieve integration of pTrc-nanEM gene cassette into the chromosome of Escherichia coli, first amplify the nanEM segment (i.e. pTrc-nanEM) of Trc promoter, as well as the kanamycin resistence gene segment with FLP recognition site (FRT site) at its both ends: FRT-Kanr-FRT (fKanrf), and splice them. Then design homologous primers for deletion of the nagE gene sequence, and using the spliced segment of pTrc-nanEM and fKanrf as template, amplify the linear DNA full-length segment for targeting of Red recombination.

(374) The specific operating process is provided below:

(375) (1) PCR Amplification of pTrc-nanEM Segment Template: nanEM/pTrc99A.

(376) Primer Design: Forward primer (Trcff-F) SEQ ID No.20, and reverse primer (Trcff-R) SEQ ID No.21.

(377) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(378) Product Size: 0.86 kb.

(379) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(380) (2) fKanrf segment amplified by PCR

(381) Primer Design: Forward primer (mfKanf-F) SEQ ID No.1, and reverse primer (mfKanf-R) SEQ ID No.2.

(382) Template: pPic9K.

(383) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(384) fKanrf size: 1.28 kb. Its nucleotide sequence is SEQ ID No.3.

(385) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(386) (3) Amplification of fKanrf spliced with pTrc-nanEM

(387) Primer Design: Forward primer (fKanf-F) SEQ ID No.22, and reverse primer (fKanf-R) SEQ ID No.23.

(388) Template: fKanrf.

(389) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(390) fKanrf size from secondary amplificatino: 1.3 kb.

(391) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(392) (4) Preparation of Linear DNA Full-length PCR Segment for Targeting of Red Recombination

(393) Design of Homologous Arm Primers: Design again homologous arm primers for deletion of the nagE gene sequence: Forward primer (nagEKO-F2) SEQ ID No.24, and reverse primer (nagEKO-R2) SEQ ID No.25.

(394) Template: Mix pTrc-nanEM PCR segment, and fKanrf PCR segment from secondary amplification in the ratio of 1:1.PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(395) Amplification Product: Homologous Arm+pTrc-nanEM-fKanrf+Homologous Arm

(396) The PCR product is separated by agarose gel electrophoresis, and purified and recovered to obtain 100 ng/μL linear DNA full-length PCR segment for targeting of Red recombination.

(397) (5) Red Recombination Operation

(398) First, pKD46 carrier is introduced into the AT-004-02 strain of Escherichia coli. Then, the prepared linear DNA segment for targeting is electrotransformed, and positive clones are screened. Finally, the resistance gene is removed.

(399) 1) Transformation of pKD46 Plasmid

(400) {circle around (1)} Preparation of Competence: First, inoculate the bacterial suspension of Escherichia coli AT-004-02 stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h. Then add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min. Finally, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(401) {circle around (2)} Plasmid Transformation: Transfer 250 μL of spontaneously sedimented thalli, add μL of pKD46 plasmid, and cultivate at −4° C. for 30 min. Then heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h. Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate. Cultivate overnight (for 12-16 h) at 30° C. Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification. Store the positive strain for use.

(402) 2) Electrotransform linear DNA segment for targeting, and screen positive clone

(403) {circle around (1)} Preparation of Electrotransformed Competence: Inoculate the AT-004-02 strain of Escherichia coli, containing pKD46, into a test tube of LB medium containing Ampicillin (Amp), and shake-cultivate at 250 rpm, on the next day, inoculate in a ratio of 1% into LB medium containing Amp, and cultivate at 30° C.; when OD600 reaches approximately 0.2, add 0.2% L-Arabinose, and induce at 30° C. for 35 min until OD600 reaches approximately 0.4. Cool on an ice bath. Wash once with ultrapure water, wash twice with 10% glycerin, and finally resuspend with 10% glycerin; the amount of glyerin used is to produce a final concentration of the thalli concentrated by 500-1000 folds.

(404) {circle around (2)} Transformation by electric shock: Take out a 2-mm electrotransformation cup from 70% ethanol, wash with sterilized ultrapure water, and irradiate by UV lamp for 30 min. Precool at 4° C. for 30 min. Transfer 90 μL of finally resuspended cells to a precooled centrifuge tube, add 5 μL (more than 100 ng) of the full-length PCR segement (linear DNA) obtained in Step (4), suction gently by a gun, and maintain on an ice bath for 30 min. Electrotransformation Parameters: 2500V, 200Ω, 25 μF.

(405) {circle around (3)} Resuscitate and screen positive clones: add 1 mL of LB broth medium, and cultivate at 37° C. and 100 rpm for 1 h. Then smear one kanamycin (Kan) plate with every 200 μL, 5 plates in total. Smear evenly and allow to air-dry. Cultivate at 30° C. for 24 h. Pick up clones grown under kanamycin resistance, and carry out PCR identification to screen positive clones.

(406) No. of the obtained strain: AT-031-01 (AT-004-02, Δ nagE::pTrc-nanEM-fKanrf).

(407) (6) Removal of the Resistance Gene

(408) Introduce pCP20 into the above kanamycin-resistant clones, cultivate at 30° C. for 8 h, then increase to 42° C. and cultivate overnight, and thermally induce to express FLP recombinase; the plasmids are lost gradually. Streak the plate of antibiotics-free culture medium by an inoculating loop dipped in the bacterial suspension, pick up grown monoclones and dot on the kanamycin-resistant plate; those that cannot grown are clones of which the kanamycin resistance gene has been removed by FLP recombination. Carry out PCR with identification primer to identify clones losing kanamycin resistance.

(409) No. of the obtained strain: AT-031-02 (AT-004-02, Δ nagE::pTrc-nanEM).

(410) 5. Influence of the integration of pTrc-nanEM gene cassette on the output of N-Acetyl-D-Glucosamine

(411) Carry out a shake-flask fermentation trial with the recombinant strain AT-031-02 of which the nagE gene site in the chromosome is integrated with pTrc-nanEM gene cassette, and the reference strain. Transfer the monoclonal strain freshly cultivated in culture medium of the LB plate, inoculate into a test tube (13×150 mm) containing 3 mL of the LB broth culture medium, and shake-cultivate at 30° C. and 225 rpm for 8 h. Then transfer the seed culture solution, inoculate in 3% into a 250-mL shake-flask containing 50 mL of the fermentation culture solution (M9 culture solution). The initial OD600 is approximately 0.5; shake-cultivate at 37° C. and 225 rpm. The fermentation cycle is 72 h. At 24 h and 48 h, adjust to pH 7.0 with 10M NaOH. According to glucose consumption in the fermentation broth, add 65% glucose solution to maintain a glucose concentration of 20 g/L. After completion of fermentation, transfer 1 mL of the fermentation broth and centrifugate. Measure the content of N-Acetyl-D-Glucosamine by HPLC method.

(412) See Table 9 for the output from shake-flask fermentation. The results show that: The output by the reference strain AT-005-02 is very low and is not detected, while the output by the recombinant strain AT-031-02 integrated with pTrc-nanEM gene cassette is increased obviously, and is also increased significantly than that by the unmutant reference strain AT-030-02.

(413) TABLE-US-00010 TABLE 9 Output from Shake-flask Fermentation by the Recombinant Strain integrated with pTrc-nanEM Gene Cassette Output of N-Acetyl-D-Glucosamine species (g/L) AT-005-02 (AT-004-02, .sup.Δ nagE) (Reference) Not detected AT-030-02 (AT-004-02, .sup.Δ nagE::pTrc-nanE) 2.6 ± 0.5 AT-031-02 (AT-004-02, .sup.Δ nagE::pTrc-nanEM) 5.9 ± 0.8

(414) The above results show that: The output of N-Acetyl-D-Glucosamine may be 5 increased obviously by overexpression of N-Acetyl-D-Mannosamine-6-P Epimerase; moreover, the output of N-Acetyl-D-Glucosamine may also be greatly by the mutant screened by error-prone PCR technology, due to increased activities of the obtained mutant of the epimerase.

Example 3.c

(415) This implementation example describes Escherichia coli strains integrated with pTrc-nanEM gene cassette, and the gene vhb thereof and its mutant for expression of vitreoscilla hemoglobin (Vhb) as well as influence on the output of N-Acetyl-D-Glucosamine.

(416) Amplify the gene vhb for vitreoscilla hemoglobin (Vhb), insert into pTrc99A, so that vhb is controlled by Trc promoter to transform the strains, or screen a mutant of the gene vhb for vitreoscilla hemoglobin (Vhb) and insert into pTrc99A to transform the strains, to increase the microorganism's utilization ability for dissolved oxygen and increase the fermentation production the output of N-Acetyl-Glucosamine.

(417) 1. Escherichia coli strains integrated with pTrc-nanEM gene cassette, and the gene vhb for expression of vitreoscilla hemoglobin (Vhb)

(418) (1) Amplify the vhb Gene and Insert into pTrc99A

(419) The nucleotide sequence the gene encoding vitreoscilla hemoglobin (Vhb) is SEQ ID No. 60, and the amino acid sequence is SEQ ID No.61. Based on the preference cocon bases of Escherichia coli, optimize and synthesize the gene for vitreoscilla hemoglobin (Vhb), and load into pUC57 carrier. Obtain a carrier named as: vhb/pUC57.

(420) Primer Design: Forward primer (vhb-F) SEQ ID No.62, and reverse primer (vhb-R) SEQ ID No.63.

(421) Template: vhb/pUC57.

(422) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(423) Amplification Product Size: 441 bp.

(424) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(425) Digest enzymatically the obtained PCR amplification segment and carrier pTrc99A with Nco I and Hind III, separate by agarose gel electrophoresis, purify and recover vhb segment and pTrc99A segment, ligate overnight with T4 DNA ligase at 16° C., and carry out identification to obtain vhb/pTrc99A plasmid.

(426) (2) Transform Escherichia coli strains integrated with pTrc-NanEM gene gassette by vhb/pTrc99A 1) Preparation of Competence

(427) {circle around (1)} Inoculate the bacterial suspension of AT-031-02 stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h.

(428) {circle around (2)} Add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min.

(429) {circle around (3)} Centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(430) 2) Plasmid Transformation

(431) {circle around (1)} Transfer 250 μL of spontaneously sedimentated thalli, add 5 μL of vhb/pTrc99A plasmid, and cultivate at −4° C. for 30 min.

(432) {circle around (2)} Heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h.

(433) {circle around (3)} Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate.

(434) {circle around (4)} Cultivate overnight (for 12-16 h) at 30° C.

(435) {circle around (5)} Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification.

(436) {circle around (6)} Positive clones are stored for use.

(437) No. of the obtained strain: AT-054 (AT-031-02, vhb/pTrc99A).

(438) 2. Escherichia coli strains integrated with pTrc-nanEM gene cassette, and the gene vhb mutant for expression of vitreoscilla hemoglobin (Vhb)

(439) 1) Preparation of Competence

(440) {circle around (1)} Inoculate the bacterial suspension of AT-031-02 stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h.

(441) {circle around (2)} Add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min.

(442) {circle around (3)} Centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(443) 2) Plasmid Transformation

(444) {circle around (1)} Transfer 250 μL of spontaneously sedimentated thalli, add 5 μL of vhbM/pTrc99A plasmid, and cultivate at −4° C. for 30 min.

(445) {circle around (2)} Heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h.

(446) {circle around (3)} Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate.

(447) {circle around (4)} Cultivate overnight (for 12-16 h) at 30° C.

(448) {circle around (5)} Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification.

(449) {circle around (6)} Positive clones are stored for use.

(450) No. of the obtained strain: AT-055 (AT-031-02, vhbM/pTrc99A).

(451) 2. Escherichia coli strains integrated with pTrc-nanEM gene cassette, and the gene vhb thereof and its mutants for expression of vitreoscilla hemoglobin (Vhb) as well as influence on the output of N-Acetyl-D-Glucosamine

(452) Carry out a shake-flask fermentation trial with the strains integrated with pTrc-nanEM gene cassette, and the mutant strains AT-052 and AT-053 with the gene vhb for expression of vitreoscilla hemoglobin. Transfer the monoclonal strain freshly cultivated in culture medium of the LB plate, inoculate into a test tube (13×150 mm) containing 3 mL of the LB broth culture medium, and shake-cultivate at 30° C. for 8 h. Then transfer the seed culture solution, inoculate in 3% into a 250-mL shake-flask containing 50 mL of M9 culture solution. The initial OD.sub.600 is approximately 0.5; shake-cultivate at 37° C. and 225 rpm. The fermentation cycle is 72 h. At 24 h and 48 h, adjust to pH 7.0 with 10M NaOH. According to glucose consumption in the fermentation broth, add 65% glucose solution to maintain a glucose concentration of 20 g/L. After completion of fermentation, transfer 1 mL of the fermentation broth and centrifugate. Measure the content of N-Acetyl-D-Glucosamine by HPLC method.

(453) See Table 10 for the output from shake-flask fermentation by recombinant strains. The results show that: The output may be increased obviously from expression of vhb by the recombinant strains both with transformed vhb/pTrc99A and with transformed vhbM/pTrc99A plasmid; moreover, the output is increased more significant by the recombinant strain with transformed vhbM/pTrc99A plasmid.

(454) TABLE-US-00011 TABLE 10 Output from Shake-flask Fermentation by the Recombinant Strains for Expression of vhb and vhbM Output of N-Acetyl-D-Glucosamine Species (g/L) AT-031-02 (Reference)  6.0 ± 0.8 AT-054 (AT-031-02, vhb/pTrc99A) 17.1 ± 1.2 AT-055 (AT-031-02, vhbM/pTrc99A) 20.7 ± 1.3

Example 4.a

(455) This example describes gene wecB cloning of UDP-N-Acetyl-D-Glucosamine-2-Epimerase (WecB), and transformed wecB/pTrc99A plasmids in Escherichia coli, as well as integration of ptrc-wecB gene cassette into the chromosome of Escherichia coli.

(456) 1. wecB Gene Cloning, Transformation of wecB/pTrc99A Plasmidin Escherichia coli, and its Influence on the Output of N-Acetyl-D-Glucosamine

(457) The gene wecB of UDP-N-AcetylGlucosamine-2-Epimerase (WecB) is controlled by Trc promoter to transform strains for overexpression of the enzyme, to strengthen production of ManNAc (N-Acetyl-D-mannosamine, N-Acetyl-D-Mannosamine or N-Acetyl-D-Mannosamine) from UDP-GlcNAc (UDP-N-Acetyl Glucosamine, UDP-N-Acetyl-D-Glucosamine).

(458) 2. wecB Gene Cloning of Escherichia coli

(459) According to NCBI, look up the nucleotide sequence SEQ ID No.49 of the wecB gene of Escherichia coli, and its amino acid sequence is SEQ ID No.50.

(460) Primer Design: Forward primer (TrcwecB-F) SEQ ID No.51, and reverse prime (TrcwecB-R) SEQ ID No.52.

(461) Template: AT-001 (Escherichia coli ATCC 27325) Genome.

(462) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(463) Amplification Product Size: 1.13 kb.

(464) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(465) Ligate the obtained PCR amplification segment with pUC57-T carrier, and carry out sequencing for identification, to obtain wecB/pUC57.

(466) 2) Construction and Transformation of Plasmid in which wecB gene is controlled by Trc promoter

(467) {circle around (1)} Plasmid Construction: Amplify plasmid wecB/pUC57, digest enzymatically wecB/pUC57 and carrier pTrc99A with Nco I and Hind III, separate by agarose gel electrophoresis, purify to recover wecB segment and pTrc99A segment, ligate overnight with T4 DNA ligase at 16° C., and carry out identification to obtain wecB/pTrc99A plasmid.

(468) {circle around (2)} Preparation of Competence: First, inoculate the bacterial suspension of AT-005-02 stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h. then add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min. Finally, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(469) {circle around (3)} Plasmid Transformation: Transfer 250 μL of spontaneously sedimentated thalli, add 5 μL of wecB/pTrc99A plasmid, and cultivate at −4° C. for 30 min. Then heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h. Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate. Cultivate overnight (for 12-16 h) at 30° C. Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification. Store the positive strain for use. Obtain Recombinant Strain wecB/pTrc99A (AT-005-02)

(470) 3. Influence of wecB/pTrc99A plasmid transformation on the output of N-Acetyl-D-Glucosamine

(471) Carry out a shake-flask fermentation trial with the recombinant strain wecB/pTrc99A (AT-005-02) and the reference strain. Transfer the monoclonal strain freshly cultivated in culture medium of the LB plate, inoculate into a test tube (13×150 mm) containing 3 mL of the LB broth culture medium, and shake-cultivate at 30° C. and 225 rpm for 8 h. Components of LB Broth Medium: 5 g/L yeast powder, 10 g/L peptone, and 10 g/L NaCl. Then transfer the seed culture solution, inoculate in 3% into a 250-mL shake-flask containing 50 mL of the fermentation culture solution (M9 culture solution). The initial OD.sub.600 is approximately 0.5; shake-cultivate at 37° C. and 225 rpm. The fermentation cycle is 72 h. At 24 h and 48 h, adjust to pH 7.0 with 10M NaOH. According to glucose consumption in the fermentation broth, add 65% glucose solution to maintain a glucose concentration of 20 g/L. After completion of fermentation, transfer 1 mL of the fermentation broth and centrifugate. Measure the content of N-Acetyl-D-Glucosamine by HPLC method.

(472) See Table 11 for the output from shake-flask fermentation. The results show that: The output by the reference strain AT-005-02 is very low and is not detected, while the output from overexpression by wecB gene of wecB/pTrc99A (AT-005-02), controlled by Trc promoter, is increased obviously.

(473) TABLE-US-00012 TABLE 11 Output from Shake-flask Fermentation by the Recombinant Strain wecB/pTrc99A (AT-005-02) Output of N-Acetyl-D-Glucosamine species (g/L) AT-005-02 (AT-004-02, .sup.Δ nagE) (Reference) Not detected wecB/pTrc99A (AT-005-02) 4.2 ± 0.4

(474) 2. Integration of pTrc-wecB Gene Cassette into the Chromosome of Escherichia coli

(475) Using the nagE gene site as integration site of pTrc-wecB gene cassette into the chromosome. To achieve integration of pTrc-wecB gene cassette into the chromosome of Escherichia coli, first amplify the wecB segment (i.e. pTrc-wecB) of Trc promoter, as well as the kanamycin resistance gene segment with FLP recognition site (FRT site) at its both ends: FRT-Kanr-FRT (fKanrf), and splice them. Then design homologous primers for deletion of the nagE gene sequence, and using the spliced segment of pTrc-wecB and fKanrf as template, amplify the linear DNA full-length segment for targeting of Red recombination.

(476) The specific operating process is provided below:

(477) (1) PCR Amplification of pTrc-wecB Segment Template: wecB/pTrc99A.

(478) Primer Design: Forward primer (Trcff-F) SEQ ID No.20, and reverse primer (Trcff-R) SEQ ID No.21.

(479) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(480) Product Size: 1.3 kb.

(481) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(482) (2) fKanrf segment amplified by PCR

(483) Primer Design: Forward primer (mfKanf-F) SEQ ID No.1, and reverse primer (mfKanf-R) SEQ ID No.2.

(484) Template: pPic9K.

(485) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(486) fKanrf size: 1.28 kb. Its nucleotide sequence is SEQ ID No.3.

(487) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(488) (3) Amplification of fKanrf spliced with pTrc-wecB

(489) Primer Design: Forward primer (fKanf-F) SEQ ID No.22, and reverse primer (fKanf-R) SEQ ID No.23.

(490) Template: fKanrf.

(491) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(492) fKanrf size from secondary amplificatino: 1.3 kb.

(493) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(494) (4) Preparation of Linear DNA Full-length PCR Segment for Targeting of Red Recombination

(495) Design of Homologous Arm Primers: Design again homologous arm primers for deletion of the nagE gene sequence: Forward primer (nagEKO-F2) SEQ ID No.24, and reverse primer (nagEKO-R2) SEQ ID No.25.

(496) Template: Mix pTrc-wecB PCR segment, and fKanrf PCR segment from secondary amplification in the ratio of 1:1.

(497) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(498) Amplification Product: Homologous Arm+pTrc-wecB-fKanrf+Homologous Arm

(499) The PCR product is separated by agarose gel electrophoresis, and purified and recovered to obtain 100 ng/μL linear DNA full-length PCR segment for targeting of Red recombination.

(500) (5) Red Recombination Operation

(501) First, pKD46 carrier is introduced into the AT-004-02 strain of Escherichia coli. Then, the prepared linear DNA segment for targeting is electrotransformed, and positive clones are screened. Finally, the resistance gene is removed.

(502) 1) Transformation of pKD46 Plasmid

(503) {circle around (1)} Preparation of Competence: First, inoculate the bacterial suspension of Escherichia coli AT-004-02 stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h. then add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min. Finally, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(504) {circle around (2)} Plasmid Transformation: Transfer 250 μL of spontaneously sedimented thalli, add 5 μL of pKD46 plasmid, and cultivate at −4° C. for 30 min. Then heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h. Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate. Cultivate overnight (for 12-16 h) at 30° C. Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification. Store the positive strain for use.

(505) 2) Electrotransform linear DNA segment for targeting, and screen positive clone

(506) {circle around (1)} Preparation of Electrotransformed Competence: Inoculate the AT-004-02 strain of Escherichia coli, containing pKD46, into a test tube of LB medium containing Ampicillin (Amp), and shake-cultivate at 250 rpm, on the next day, inoculate in a ratio of 1% into LB medium containing Amp, and cultivate at 30° C.; when OD600 reaches approximately 0.2, add 0.2% L-Arabinose, and induce at 30° C. for 35 min until OD600 reaches approximately 0.4. Cool on an ice bath. Wash once with ultrapure water, wash twice with 10% glycerin, and finally resuspend with 10% glycerin; the amount of glyerin used is to produce a final concentration of the thalli concentrated by 500-1000 folds.

(507) {circle around (2)} Transformation by electric shock: Take out a 2-mm electrotransformation cup from 70% ethanol, wash with sterilized ultrapure water, and irradiate by UV lamp for 30 min. Precool at 4° C. for 30 min. Transfer 90 μL of finally resuspended cells to a precooled centrifuge tube, add 5 μL (more than 100 ng) of the full-length PCR segement (linear DNA) obtained in Step (4), suction gently by a gun, and maintain on an ice bath for 30 min. Electrotransformation Parameters: 2500V, 200Ω, 25 μF.

(508) {circle around (3)} Resuscitate and screen positive clones: add 1 mL of LB broth medium, and cultivate at 37° C. and 100 rpm for 1 h. Then smear one kanamycin (Kan) plate with every 200 μL, 5 plates in total. Smear evenly and allow to air-dry. Cultivate at 30° C. for 24 h. Pick up clones grown under kanamycin resistance, and carry out PCR identification to screen positive clones.

(509) No. of the obtained strain: AT-042-01 (AT-004-02, Δ nagE::pTrc-wecB-fKanrf).

(510) (6) Removal of the Resistance Gene

(511) Introduce pCP20 into the above kanamycin-resistant clones, cultivate at 30° C. for 8 h, then increase to 42° C. and cultivate overnight, and thermally induce to express FLP recombinase; the plasmids are lost gradually. Streak the plate of antibiotics-free culture medium by an inoculating loop dipped in the bacterial suspension, pick up grown monoclones and dot on the kanamycin-resistant plate; those that cannot grown are clones of which the kanamycin resistance gene has been removed by FLP recombination. Carry out PCR with identification primer to identify clones losing kanamycin resistance.

(512) No. of the obtained strain: AT-042-02 (AT-004-02, Δ nagE::pTrc-wecB).

(513) 3. Influence of the integration of pTrc-wecB gene cassette on the output of N-Acetyl-D-Glucosamine

(514) Carry out a shake-flask fermentation trial with the recombinant strain AT-042-02 of which the nagE gene site in the chromosome is integrated with pTrc-wecB gene cassette, and the reference strain. Transfer the monoclonal strain freshly cultivated in culture medium of the LB plate, inoculate into a test tube (13×150 mm) containing 3 mL of the LB broth culture medium, and shake-cultivate at 30° C. and 225 rpm for 8 h. Then transfer the seed culture solution, inoculate in 3% into a 250-mL shake-flask containing 50 mL of the fermentation culture solution (M9 culture solution). The initial OD.sub.600 is approximately 0.5; shake-cultivate at 37° C. and 225 rpm. The fermentation cycle is 72 h. At 24 h and 48 h, adjust to pH 7.0 with 10M NaOH. According to glucose consumption in the fermentation broth, add 65% glucose solution to maintain a glucose concentration of 20 g/L. After completion of fermentation, transfer 1 mL of the fermentation broth and centrifugate. Measure the content of N-Acetyl-D-Glucosamine by HPLC method.

(515) See Table 12 for the output from shake-flask fermentation. The results show that: The outputs by the reference strains AT-001 and AT-005-02 are very low and are not detected, while the output by the recombinant strain integrated with pTrc-wecB gene cassette is increased obviously, and is also increased significantly than that by the recombinant strain wecB/pTrc99A (AT-005-02) not integrated with the gene cassette.

(516) TABLE-US-00013 TABLE 12 Output from Shake-flask Fermentation by the Recombinant Strain integrated with pTrc-wecB Gene Cassette Output of N-Acetyl-D-Glucosamine species (g/L) AT-001 (Reference) Not detected AT-005-02 (AT-004-02, .sup.Δ nagE) (Reference) Not detected wecB/pTrc99A (AT-005-02) 4.1 ± 0.5 AT-042-02 (AT-004-02, .sup.Δ nagE::pTrc-wecB) 7.0 ± 0.8

Example 4.b

(517) This implementation example describes screening for a gene mutant of UDP-N-AcetylGlucosamine-2-Epimerase (WecB); the said gene encodes UDP-N-AcetylGlucosamine-2-Epimerase (WecB) with increased activities.

(518) To further increase synthetic quantity of N-Acetyl-D-Glucosamine by the production strain, screen a gene mutant ncoding UDP-N-AcetylGlucosamine-2-Epimerase with increased activities. To achieve the purpose, amplify the cloned gene by error-prone PCR technology; used for amplified DNA polymerase, amplify the said gene under conditions leading to high-frequency mismatch, so as to obtain a high-frequency mutation in PCR products.

(519) The specific operating process is provided below:

(520) 1. Amplification of UDP-N-AcetylGlucosamine-2-Epimerase gene wecB by Error-prone PCR.

(521) By means of Taq DNA polymerase without the property of 3′-5′ proofreading function, control the frequency of random mutation under high magnesium ion concentration (8 mmol/L) and different dNTP concentrations (where, the concentration of dATP and dGTP is 1.5 mmol/L; and the concentration of dTTP and dCTP is 3.0 mmol/L), introduce random mutations into the target gene, and construct a mutant library; the template concentration A260 value is 1000 ng/mL, the enzyme concentration is 5 U/μL, and the primer concentration is 100 μM.

(522) Error-prone PCR reaction system (50 μL): 10×PCR reaction buffer 5 μl, dNTP (2.5 mM) 5 μL, MgCl.sub.2 (25 mM) 5 μL, Forward primer (TrcwecB-F, SEQ ID No.51) μL, reverse primer (TrcwecB-R, SEQ ID No.52) 1 μL, DNA template (wecB/pUC57) 0.1 μL, Taq DNA polymerase 0.5 μL, and ddH.sub.2O 32.4 μL.

(523) PCR procedure: Predegenerate at 96° C. for 4 min; degenerate at 94° C. for 1 min, anneal at 56° C. for 1 min, extend at 75° C. for 2 min, and repeat for 45 cycles; finally extend at 75° C. for 15 min, recover PCR product (product size: 1.13 kb) by gel recovery method; transfer 5 μL of the product and carry out 1% agarose gel electrophoresis test; the product is store at −20° C. for use.

(524) 2. Construction of the gene mutant library of UDP-N-Acetyl Glucosamine-2-Epimerase

(525) Digest the above PCR product by two enzymes of restriction endonuclease Nco I and Hind III, carry out a ligation reaction with pTrc99A digested by Nco I and Hind III, then transform Escherichia coli AT-005-02 with the mixture of the ligated products to obtain a large amount of cloned transformants, and construct a mutant library of transformed thalli.

(526) 3. Screening for Mutants with High Enzyme Activities

(527) Using the wild type WecB/pTrc99A (AT-005-02) as reference, pick up randomly 640 mutant clones from the mutant library of transformed thalli, inoculate into 5 mL of LB medium containing 50 μg/mL Ampicillin (Amp), shake-cultivate at 37° C. and 150 rpm for 18 h, and then centrifugate at 10000 rpm for 5 mim and collect thalli. Discard the supernatant, then resuspend at 4° C. in 1 mL of PBS solution (pH 7.5, 10 mmol/L), carry out ultrasonicate at a voltage of 300 V for 10 min (ultrasonicate for 3 s and pause for 6 s), centrifugate, transfer the supernatant as crude extract of enzyme, and carry out a method for determination of enzyme activity.

(528) Determination of UDP-N-AcetylGlucosamine-2-Epimerase Activity: Based on the amount of UDP-N-Acetyl-D-Glucosamine transformed into N-Acetyl-D-Mannosamine. That is to say, the reduced amount of UDP-N-Acetyl-D-Glucosamine is used as test marker. Definition of Enzyme Activity Unit: Under the enzymatic reaction conditions, the enzyme amount reduced, equivalent to 1 μmol UDP-N-Acetyl-D-Glucosamine per minute, is defined as one enzyme activity unit (IU). The specific procedure is provided as follows: Transfer 20 mL of the reaction system as the system for determination of enzyme activity, which contains 45 mmol/L phosphate buffer (pH7.5), 10 mM MgC12 and 100 nCi of UDPGlcNAc, and 5 mg crude enzyme solution. Carry out the enzyme activity reaction by incubating on a water bath at 37° C. for 30 min. Add alcohol to stop the reaction. Separate radioactive compounds by paper chromatography. Measure the radioactive intensity by a liquid scintillation counter. The solvent system used is a mixture of n-propanol:1 M sodium acetate, pH 5.0:water (7:1:2). Calculate the activity units of UDP-N-AcetylGlucosamine-2-Epimerase, based on the amount of UDPGlcNAc transformed into ManNAc.

(529) The results show that: The enzyme activity of the mutant strain with maximum activity is 653 IU/mL, and the enzyme activity of the reference control is 21.0 IU/mL. Transform WecB by error-prone PCR, to obtain a mutant strain with enzyme activity increased greatly. Pick up the mutant strain with maximum enzyme activity and extract plasmids for sequencing. The results show that: The mutant gene sequence of UDP-N-AcetylGlucosamine-2-Epimerase is shown as SEQ ID No.58, and the corresponding amino acid sequence is shown as SEQ ID No.59. Compared with gene sequence of the wild type UDP-N-AcetylGlucosamine-2-Epimerase, 5 base point mutations occur in total: 101G/C, 433C/G, 677G/T, 734T/G, and 1038T/C; There occur 4 missense mutations of amino acids, of which the mutation points are: C34S (cysteine at Site 34 is replaced by serine), H145D (histidine at Site 145 is replaced by aspartate), C226F (cysteine at Site 226 is replaced by phenylalanine), and V245G (valine at Site 245 is replaced by glycine). The mutant gene is named as wecBM.

(530) 4. Integration of pTrc-wecBM Gene Cassette into the nagE Gene Site in the Chromosome of Escherichia coli

(531) Using the nagE gene site as integration site of pTrc-wecBM gene cassette into the chromosome. To achieve integration of pTrc-wecBM gene cassette into the chromosome of Escherichia coli, first amplify the wecBM segment (i.e. pTrc-wecBM) of Trc promoter, as well as the kanamycin resistence gene segment with FLP 10 recognition site (FRT site) at its both ends: FRT-Kanr-FRT (fKanrf), and splice them. Then design homologous primers for deletion of the nagE gene sequence, and using the spliced segment of pTrc-wecBM and fKanrf as template, amplify the linear DNA full-length segment for targeting of Red recombination.

(532) The specific operating process is provided below:

(533) (1) PCR Amplification of pTrc-wecBM Segment Template: wecBM/pTrc99A.

(534) Primer Design: Forward primer (Trcff-F) SEQ ID No.20, and reverse primer (Trcff-R) SEQ ID No.21.

(535) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(536) Product Size: 1.3 kb.

(537) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(538) (2) fKanrf segment amplified by PCR

(539) Primer Design: Forward primer (mfKanf-F) SEQ ID No.1, and reverse primer (mfKanf-R) SEQ ID No.2.

(540) Template: pPic9K.

(541) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(542) fKanrf size: 1.28 kb. Its nucleotide sequence is SEQ ID No.3.

(543) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(544) (3) Amplification of fKanrf spliced with pTrc-wecBM

(545) Primer Design: Forward primer (fKanf-F) SEQ ID No.22, and reverse primer (fKanf-R) SEQ ID No.23.

(546) Template: fKanrf.

(547) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(548) fKanrf size from secondary amplificatino: 1.3 kb.

(549) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(550) (4) Preparation of Linear DNA Full-length PCR Segment for Targeting of Red Recombination

(551) Design of Homologous Arm Primers: Design again homologous arm primers for deletion of the nagE gene sequence: Forward primer (nagEKO-F2) SEQ ID No.24, and reverse primer (nagEKO-R2) SEQ ID No.25.

(552) Template: Mix pTrc-wecBM PCR segment, and fKanrf PCR segment from secondary amplification in the ratio of 1:1.

(553) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(554) Amplification Product: Homologous Arm+pTrc-wecBM-fKanrf+Homologous Arm

(555) The PCR product is separated by agarose gel electrophoresis, and purified and recovered to obtain 100 ng/μL linear DNA full-length PCR segment for targeting of Red recombination.

(556) (5) Red Recombination Operation

(557) First, pKD46 carrier is introduced into the AT-004-02 strain of Escherichia coli. Then, the prepared linear DNA segment for targeting is electrotransformed, and positive clones are screened. Finally, the resistance gene is removed.

(558) 1) Transformation of pKD46 Plasmid

(559) {circle around (1)} Preparation of Competence: First, inoculate the bacterial suspension of Escherichia coli AT-004-02 stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h. Then add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min. Finally, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(560) {circle around (2)} Plasmid Transformation: Transfer 250 μL of spontaneously sedimented thalli, add 5 μL of pKD46 plasmid, and cultivate at −4° C. for 30 min. Then heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h. Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate. Cultivate overnight (for 12-16 h) at 30° C. Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification. Store the positive strain for use.

(561) 2) Electrotransform linear DNA segment for targeting, and screen positive clone

(562) {circle around (1)} Preparation of Electrotransformed Competence: Inoculate the AT-004-02 strain of Escherichia coli, containing pKD46, into a test tube of LB medium containing Ampicillin (Amp), and shake-cultivate at 250 rpm, on the next day, inoculate in a ratio of 1% into LB medium containing Amp, and cultivate at 30° C.; when OD600 reaches approximately 0.2, add 0.2% L-Arabinose, and induce at 30° C. for 35 min until OD600 reaches approximately 0.4. Cool on an ice bath. Wash once with ultrapure water, wash twice with 10% glycerin, and finally resuspend with 10% glycerin; the amount of glyerin used is to produce a final concentration of the thalli concentrated by 500-1000 folds.

(563) {circle around (2)} Transformation by electric shock: Take out a 2-mm electrotransformation cup from 70% ethanol, wash with sterilized ultrapure water, and irradiate by UV lamp for 30 min. Precool at 4° C. for 30 min. Transfer 90 μL of finally resuspended cells to a precooled centrifuge tube, add 5 μL (more than 100 ng) of the full-length PCR segement (linear DNA) obtained in Step (4), suction gently by a gun, and maintain on an ice bath for 30 min. Electrotransformation Parameters: 2500V, 200Ω, 25 μF.

(564) {circle around (3)} Resuscitate and screen positive clones: add 1 mL of LB broth medium, and cultivate at 37° C. and 100 rpm for 1 h. Then smear one kanamycin (Kan) plate with every 200 μL, 5 plates in total. Smear evenly and allow to air-dry. Cultivate at 30° C. for 24 h. Pick up clones grown under kanamycin resistance, and carry out PCR identification to screen positive clones. No. of the obtained strain: AT-043-01 (AT-004-02, Δ nagE::pTrc-wecBM-fKanrf).

(565) (6) Removal of the Resistance Gene

(566) Introduce pCP20 into the above kanamycin-resistant clones, cultivate at 30° C. for 8 h, then increase to 42° C. and cultivate overnight, and thermally induce to express FLP recombinase; the plasmids are lost gradually. Streak the plate of antibiotics-free culture medium by an inoculating loop dipped in the bacterial suspension, pick up grown monoclones and dot on the kanamycin-resistant plate; those that cannot grown are clones of which the kanamycin resistance gene has been removed by FLP recombination. Carry out PCR with identification primer to identify clones losing kanamycin resistance.

(567) No. of the obtained strain: AT-043-02 (AT-004-02, Δ nagE::pTrc-wecBM).

(568) (5) Influence of the integration of pTrc-wecBM gene cassette on the output of N-Acetyl-D-Glucosamine

(569) Carry out a shake-flask fermentation trial with the recombinant strain AT-043-02 of which the nagE gene site in the chromosome is integrated with pTrc-wecBM gene cassette, and the reference strain. Transfer the monoclonal strain freshly cultivated in culture medium of the LB plate, inoculate into a test tube (13×150 mm) containing 3 mL of the LB broth culture medium, and shake-cultivate at 30° C. and 225 rpm for 8 h. Then transfer the seed culture solution, inoculate in 3% into a 250-mL shake-flask containing 50 mL of the fermentation culture solution (M9 culture solution). The initial OD600 is approximately 0.5; shake-cultivate at 37° C. and 225 rpm. The fermentation cycle is 72 h. At 24 h and 48 h, adjust to pH 7.0 with 10M NaOH. According to glucose consumption in the fermentation broth, add 65% glucose solution to maintain a glucose concentration of 20 g/L. After completion of fermentation, transfer 1 mL of the fermentation broth and centrifugate. Measure the content of N-Acetyl-D-Glucosamine by HPLC method.

(570) See Table 13 for the output from shake-flask fermentation. The results show that: The output by the reference strain AT-005-02 is very low and is not detected, while the output by the recombinant strain AT-043-02 integrated with pTrc-wecBM gene cassette is increased obviously, and is also increased significantly than that by the unmutant reference strain AT-042-02.

(571) TABLE-US-00014 TABLE 13 Output from Shake-flask Fermentation by the Recombinant Strain integrated with pTrc-wecBM Gene Cassette Output of N-Acetyl-D-Glucosamine species (g/L) AT-005-02 (AT-004-02, .sup.Δ nagE) (Reference) Not detected AT-042-02 (AT-004-02, .sup.Δ nagE::pTrc-wecB)  7.1 ± 0.8 AT-043-02 (AT-004-02, .sup.Δ nagE::pTrc-wecBM) 10.9 ± 0.9

(572) The above results show that: The output of N-Acetyl-D-Glucosamine may be increased obviously by overexpression of UDP-N-AcetylGlucosamine-2-Epimerase; moreover, the output of N-Acetyl-D-Glucosamine may also be greatly by the mutant screened by error-prone PCR technology, due to increased activities of the obtained mutant of the epimerase.

Example 4.c

(573) This implementation example describes Escherichia coli strains integrated with wecBM gene cassette, and the gene vhb thereof and its mutant for expression of vitreoscilla hemoglobin (Vhb) as well as influence on the output of N-Acetyl-D-Glucosamine.

(574) Amplify the gene vhb for vitreoscilla hemoglobin (Vhb), insert into pTrc99A, so that vhb is controlled by Trc promoter to transform the strains, or screen a mutant of the gene vhb for vitreoscilla hemoglobin (Vhb) and insert into pTrc99A to transform the strains, to increase the microorganism's utilization ability for dissolved oxygen and increase the fermentation production the output of N-Acetyl-Glucosamine.

(575) 1. Escherichia coli strains integrated with pTrc-wecBM gene cassette, and the gene vhb for expression of vitreoscilla hemoglobin (Vhb)

(576) (1) Amplify the vhb Gene and Insert into pTrc99A

(577) The nucleotide sequence the gene encoding vitreoscilla hemoglobin (Vhb) is SEQ ID No.60, and the amino acid sequence is SEQ ID No.61. Based on the preference cocon bases of Escherichia coli, optimize and synthesize the gene for vitreoscilla hemoglobin (Vhb), and load into pUC57 carrier. Obtain a carrier named as: vhb/pUC57.

(578) Primer Design: Forward primer (vhb-F) SEQ ID No.62, and reverse primer (vhb-R) SEQ ID No.63.

(579) Template: vhb/pUC57.

(580) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(581) Amplification Product Size: 441 bp.

(582) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(583) Digest enzymatically the obtained PCR amplification segment and carrier pTrc99A with Nco I and Hind III, separate by agarose gel electrophoresis, purify and recover vhb segment and pTrc99A segment, ligate overnight with T4 DNA ligase at 16° C., and carry out identification to obtain vhb/pTrc99A plasmid.

(584) (2) Transform Escherichia coli strains integrated with pTrc-wecBM gene cassette by vhb/pTrc99A

(585) 1) Preparation of Competence

(586) {circle around (1)} Inoculate the bacterial suspension of AT-043-02 stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h.

(587) {circle around (2)} Add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min.

(588) {circle around (3)} Centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(589) 2) Plasmid Transformation

(590) {circle around (1)} Transfer 250 μL of spontaneously sedimentated thalli, add 5 μL of vhb/pTrc99A plasmid, and cultivate at −4° C. for 30 min.

(591) {circle around (2)} Heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h.

(592) {circle around (3)} Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate.

(593) {circle around (4)} Cultivate overnight (for 12-16 h) at 30° C.

(594) {circle around (5)} Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification.

(595) {circle around (6)} Positive clones are stored for use.

(596) No. of the obtained strain: AT-056 (AT-043-02, vhb/pTrc99A).

(597) 2. Escherichia coli strains integrated with pTrc-wecBM gene cassette, and the gene vhb mutant for expression of vitreoscilla hemoglobin (Vhb)

(598) 1) Preparation of Competence

(599) {circle around (1)} Inoculate the bacterial suspension of AT-043-02 stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h.

(600) {circle around (2)} Add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min.

(601) {circle around (3)} Centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(602) 2) Plasmid Transformation

(603) {circle around (1)} Transfer 250 μL of spontaneously sedimentated thalli, add 5 μL of vhbM/pTrc99A plasmid, and cultivate at −4° C. for 30 min.

(604) {circle around (2)} Heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h.

(605) {circle around (3)} Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate.

(606) {circle around (4)} Cultivate overnight (for 12-16 h) at 30° C.

(607) {circle around (5)} Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification.

(608) {circle around (6)} Positive clones are stored for use.

(609) No. of the obtained strain: AT-057 (AT-043-02, vhbM/pTrc99A).

(610) 2. Escherichia coli strains integrated with pTrc-wecBM gene cassette, and the gene vhb thereof and its mutants for expression of vitreoscilla hemoglobin (Vhb) as well as influence on the output of N-Acetyl-D-Glucosamine

(611) Carry out a shake-flask fermentation trial with the strains integrated with pTrc-wecBM gene cassette, and the mutant strains AT-056 and AT-057 with the gene vhb for expression of vitreoscilla hemoglobin. Transfer the monoclonal strain freshly cultivated in culture medium of the LB plate, inoculate into a test tube (13×150 mm) containing 3 mL of the LB broth culture medium, and shake-cultivate at 30° C. and 225 rpm for 8 h. Then transfer the seed culture solution, inoculate in 3% into a 250-mL shake-flask containing 50 mL of M9 culture solution. The initial OD.sub.600 is approximately 0.5; shake-cultivate at 37° C. and 225 rpm. The fermentation cycle is 72 h. At 24 h and 48 h, adjust to pH 7.0 with 10M NaOH. According to glucose consumption in the fermentation broth, add 65% glucose solution to maintain a glucose concentration of 20 g/L. After completion of fermentation, transfer 1 mL of the fermentation broth and centrifugate. Measure the content of N-Acetyl-D-Glucosamine by HPLC method.

(612) See Table 14 for the output from shake-flask fermentation by recombinant strains. The results show that: The output may be increased obviously from expression of vhb by the recombinant strains both with transformed vhb/pTrc99A and with transformed vhbM/pTrc99A plasmid; moreover, the output is increased more significant by the recombinant strain with transformed vhbM/pTrc99A plasmid.

(613) TABLE-US-00015 TABLE 14 Output from Shake-flask Fermentation by the Recombinant Strains Integrated with pTrc-wecBM Gene Cassette for Expression of vhb and vhbM Output of N-Acetyl-D-Glucosamine species (g/L) AT-043-02 (AT-004-02, .sup.Δ nagE::pTrc-wecBM) 10.8 ± 0.9 (reference) AT-056 (AT-043-02, vhb/pTrc99A) 17.3 ± 1.4 AT-057 (AT-043-02, vhbM/pTrc99A) 21.4 ± 1.4

Example 5.a

(614) This implementation example describes influences of the strains on the output of N-Acetyl-D-Glucosamine, of which the natural endogenous promoter of the nagB gene is replaced by Trc promoter, or the natural endogenous promoter of the glmS gene is further deleted.

(615) 1. The natural endogenous promoter of the nagB gene is replaced by Trc promoter

(616) The gene promoter of D-Glucosamine-6-Phosphate Deaminase (NagB) in nag regulon (nagE-nagBACD) is replaced by Trc promoter. The reaction catalyzed by D-Glucosamine-6-Phosphate Deaminase (NagB) is reversible; overexpression of nagB may accelerate the forward catalytic reaction by NagB, to achieve the purpose of increasing D-Glucosamine-6-Phosphate (GlcN-6-P).

(617) First, amplify Trc promoter segment and fKanrf segment, and splice together. Then design homologous primers, and amplify linear DNA full-length segment for targeting of Red recombination.

(618) (1) Amplification of Trc promoter sequence

(619) According to public information, look up Trc promoter sequence: SEQ ID No.32.

(620) Primer Design: Forward primer (KanTrcRed-F) SEQ ID No.33, and reverse primer (KanTrcRed-R) SEQ ID No.34. Template: pTrc99A

(621) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(622) Product Size: 166 bp.

(623) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(624) (2) Amplify the kanamycin resistance gene with recognition sites (FRT sites) for FLP recombinase at its both ends: fKanrf

(625) Primer Design: Forward primer (mfKanf-F) SEQ ID No.1, and reverse primer (mfKanf-R) SEQ ID No.2.

(626) Template: pPic9K.

(627) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(628) fKanrf size: 1.28 kb. Its nucleotide sequence is SEQ ID No.3.

(629) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(630) (3) Amplification of fKanrf spliced with Trc promoter

(631) Primer Design: Forward primer (fKanfRed-F1) SEQ ID No.35, and reverse primer (fKanfRed-R1) SEQ ID No.36.

(632) Template: fKanrf.

(633) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(634) fKanrf size from secondary amplificatino: 1.3 kb.

(635) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(636) (4) Preparation of Linear DNA Full-length PCR Segment for Targeting of Red Recombination

(637) Design of Homologous Arm Primers: From NCBI, look up NC_000913, nagB promoter sequence and nagA gene sequence SEQ ID No.13 of Escherichia coli str. K-12, and design the homologous arm primers for deletion of nagB promoter: Forward primer (nagBKO-F1) SEQ ID No.40 and reverse primer (nagBKO-R1) SEQ ID No.41.

(638) Template: Mix Trc promoter PCR segment and fKanrf PCR segment from secondary amplification in the ratio of 1:1.

(639) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(640) Amplification Product: Homologous Arm+fKanrf+Trc Promoter+Homologous Arm.

(641) The PCR product is separated by agarose gel electrophoresis, and purified and recovered to obtain 100 ng/μL linear DNA full-length PCR segment for targeting of Red recombination.

(642) (5) Red Recombination Operation

(643) First, pKD46 carrier is introduced into the AT-005-02 strain of Escherichia coli. Then, the prepared linear DNA segment for targeting is electrotransformed, and positive clones are screened. Finally, the resistance gene is removed.

(644) No. of the obtained strain: AT-048(AT-005-02, nagB promotor::Trc promoter).

(645) 2. Deletion of the natural endogenous promoter of the glmS gene

(646) Deletion of the gene promoter of Glucosamine-6-Phosphate Synthase (glmS). Glucosamine-6-Phosphate Synthase (GlmS), also called as L-Glutamine-D-fructose-6-phosphate aminotransferase, can catalyze amination of Glucose-6-Phosphate (Glc-6-P) into D-Glucosamine-6-Phosphate (GlcN-6-P), but has a severe problem for product inhibition. When the promoter sequence is deleted so that the enzyme cannot be expressed, it may solve product inhibition of GlcN-6-P.

(647) First, amplify fKanrf segment; then design homologous primers, and amplify linear DNA full-length segment for targeting of Red recombination.

(648) (1) Amplify the kanamycin resistance gene with recognition sites (FRT sites) for FLP recombinase at its both ends: fKanrf

(649) Primer Design: Forward primer (mfKanf-F) SEQ ID No.1, and reverse primer (mfKanf-R) SEQ ID No.2.

(650) Template: pPic9K.

(651) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(652) fKanrf size: 1.28 kb. Its nucleotide sequence is SEQ ID No.3.

(653) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(654) (2) Preparation of Linear DNA Full-length PCR Segment for Targeting of Red Recombination

(655) Design of Homologous Primers: From NCBI, look up NC_000913, the gene promoter sequence SEQ ID No.42 of Glucosamine-6-Phosphate Synthase (GlmS) of Escherichia coli str. K-12, and design the homologous arm primers for deletion of glmS gene promoter: Forward primer (ProglmsKO-F) SEQ ID No.43 and reverse primer (ProglmsKO-R) SEQ ID No. 44.

(656) Template: fKanrf PCR Segment.

(657) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(658) Amplification Product: Homologous Arm+fKanf+Homologous Arm.

(659) The PCR product is separated by agarose gel electrophoresis, and purified and recovered to obtain 100 ng/μL linear DNA full-length PCR segment for targeting of Red recombination.

(660) (3) Red Recombination Operation

(661) First, pKD46 carrier is introduced into the AT-048 strain of Escherichia coli. Then, the prepared linear DNA segment for targeting is electrotransformed, and positive clones are screened. Finally, the resistance gene is removed.

(662) No. of the obtained strain: AT-049(AT-048, Δ glmS promotor).

(663) 3. Influence of the strains of which nagB promoter replaced by a promoter with higher expression level, or glmS promoter is further deleted, on the output of N-Acetyl-D-Glucosamine

(664) Carry out a shake-flask fermentation trial with the strain of which nagB promoter is replaced by a promoter with higher expression level, and the recombinant strain of which glmS promoter is further deleted. Transfer the monoclonal strain freshly cultivated in culture medium of the LB plate, inoculate into a test tube (13×150 mm) containing 3 mL of the LB broth culture medium, and shake-cultivate at 30° C. and 225 rpm for 8 h. Then transfer the seed culture solution, inoculate in 3% into a 250-mL shake-flask containing 50 mL of the fermentation culture solution (M9 culture solution). The initial OD600 is approximately 0.5; shake-cultivate at 37° C. and 225 rpm. The fermentation cycle is 72 h. At 24 h and 48 h, adjust to pH 7.0 with 10M NaOH. According to glucose consumption in the fermentation broth, add 65% glucose solution to maintain a glucose concentration of 20 g/L. After completion of fermentation, transfer 1 mL of the fermentation broth and centrifugate. Measure the content of N-Acetyl-D-Glucosamine by HPLC method.

(665) See Table 15 for the output from shake-flask fermentation. The results show that: The output of N-Acetyl-D-Glucosamine is obviously increased by the recombinant strains of which nagB promoter is replaced by Trc promoter, or glmS promoter is further deleted.

(666) TABLE-US-00016 TABLE 15 Output from Shake-flask Fermentation by Recombinant Strains of which nagB promoter is replaced or glmS promoter is further deleted Output of N-Acetyl-D-Glucosamine species (g/L) AT-001 (Reference) Not detected AT-005-02 (Reference) Not detected AT-048(AT-005-02, .sup.Δ nagB promotor::Trc 3.3 ± 0.4 promoter) AT-049(AT-048, .sup.Δ glmS promotor) 8.7 ± 0.9

Example 5.b

(667) This implementation example describes influences of the strains on the output of N-Acetyl-D-Glucosamine, of which the natural endogenous promoter of the glmS gene is replaced by Trc promoter, and the natural endogenous promoter of the nagB gene is further deleted.

(668) 1. The natural endogenous promoter of the glmS gene is replaced by Trc promoter

(669) The gene promoter sequence of L-Glutamine-D-Fructose-6-Phosphate Aminotransferase is replaced by Trc promoter sequence. L-Glutamine-6-Phosphate Aminotransferase, also called as Glucosamine-6-Phosphate Synthase (GlmS); replacement of its promoter sequence is replaced by Trc promoter sequence may overexpress glmS, and accelerate GlmS catalytic function, to achieve the purpose of increasing D-Glucosamine-6-Phosphate (GlcN-6-P).

(670) First, amplify Trc promoter sequence segment and fKanrf segment, and splice together. Then design homologous primers, and amplify linear DNA full-length segment for targeting of Red recombination.

(671) (1) Amplification of Linear DNA Full-length PCR Segment for Targeting of Red Recombination

(672) Design of homologous arm primers: According to the glmS gene promoter sequence SEQ ID No.42, design homologous arm primers with the promoter replaced by Trc promoter: Forward primer (ProglmspTrc-F) SEQ ID No.45, and reverse primer (ProglmspTrc-R) SEQ ID No.46. Template: Mix Trc promoter PCR segment and fKanrf PCR segment from secondary amplification in the ratio of 1:1.

(673) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(674) Amplification Product: Homologous Arm+fKanrf+Trc Promoter+Homologous Arm.

(675) The PCR product is separated by agarose gel electrophoresis, and purified and recovered to obtain 100 ng/μL linear DNA full-length PCR segment for targeting of Red recombination.

(676) (2) Red Recombination Operation

(677) First, pKD46 carrier is introduced into the AT-005-02 strain of Escherichia coli. Then, the prepared linear DNA segment for targeting is electrotransformed, and positive clones are screened. Finally, the resistance gene is removed.

(678) No. of the obtained strain: AT-050 (AT-005-02, glmS promotor::Trc promoter).

(679) 2. Deletion of the natural endogenous promotor of NagB gene

(680) Deletion of the gene promoter sequence of D-Glucosamine-6-Phosphate Deaminase (NagB) in the nag regulon (nagE-nagBACD), so that nagB loses its function, may eliminate the reverse catalytic function of NagB and reduce production of Glc-6-P from GlcN-6-P.

(681) First, amplify fKanrf segment; then design homologous primers, and prepare linear DNA full-length segment for targeting of Red recombination.

(682) (1) Preparation of Linear DNA Full-length PCR Segment for Targeting of Red Recombination

(683) Design of Homologous Arm Primers: According to nagB promoter sequence and nagA gene sequence SEQ ID No.13, design the homologous arm primers for deletion of nagB promoter sequence: Forward primer (nagBKO-F2) SEQ ID No.47 and reverse primer (nagBKO-R2) SEQ ID No.48. Template: fKanrf PCR Segment PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3:

(684) Extend at 72° C. for 10 min.

(685) Amplification Product: Homologous Arm+fKanrf+Homologous Arm.

(686) The PCR product is separated by agarose gel electrophoresis, and purified and recovered to obtain 100 ng/μL linear DNA full-length PCR segment for targeting of Red recombination.

(687) (2) Red Recombination Operation

(688) First, pKD46 carrier is introduced into the AT-050 strain of Escherichia coli. Then, the prepared linear DNA segment for targeting is electrotransformed, and positive clones are screened. Finally, the resistance gene is removed.

(689) No. of the obtained strain: AT-051 (AT-050, Δ nagB promotor).

(690) 3. Influence of the strains of which glmS promoter replaced by a promoter with higher expression level, or is further deleted, on the output of N-Acetyl-D-Glucosamine

(691) Carry out a shake-flask fermentation trial with the strain of which glmS promoter is replaced by a promoter with higher expression level, and the recombinant strain of which nagB promoter is further deleted.

(692) Transfer the monoclonal strain freshly cultivated in culture medium of the LB plate, inoculate into a test tube (13×150 mm) containing 3 mL of the LB broth culture medium, and shake-cultivate at 30° C. and 225 rpm for 8 h. Then transfer the seed culture solution, inoculate in 3% into a 250-mL shake-flask containing 50 mL of the fermentation culture solution (M9 culture solution). The initial OD600 is approximately 0.5; shake-cultivate at 37° C. and 225 rpm. The fermentation cycle is 72 h. At 24 h and 48 h, adjust to pH 7.0 with 10M NaOH. According to glucose consumption in the fermentation broth, add 65% glucose solution to maintain a glucose concentration of 20 g/L. After completion of fermentation, transfer 1 mL of the fermentation broth and centrifugate. Measure the content of N-Acetyl-D-Glucosamine by HPLC method.

(693) See Table 16 for the output from shake-flask fermentation. The results show that: The output of N-Acetyl-D-Glucosamine is not obviously increased by the recombinant strains of which glmS promoter is replaced by Trc promoter, and is not detected. However, the output of N-Acetyl-D-Glucosamine is increased obviously when nagB is meanwhile deleted, than that by the reference strain.

(694) TABLE-US-00017 TABLE 16 Output from Shake-flask Fermentation by Recombinant Strains of which glmS promoter is replaced or nagB promoter is further deleted Output of N-Acetyl-D-Glucosamine species (g/L) AT-001 (Reference) Not detected AT-005-02 (Reference) Not detected AT-050 (AT-005-02, .sup.Δ glmS promotor::Trc Not detected promoter) AT-051 (AT-050, .sup.Δ nagB promotor) 5.6 ± 0.6

Example 5.c

(695) This implementation example describes Escherichia coli strains integrated of which the natural endogenous promoter of glmS gene and nagB gene is replaced and/or deleted, and the gene vhb thereof and its mutant for expression of vitreoscilla hemoglobin (Vhb) as well as influence on the output of N-Acetyl-D-Glucosamine.

(696) Amplify the gene vhb for vitreoscilla hemoglobin (Vhb), insert into pTrc99A, so that vhb is controlled by Trc promoter to transform the strains, or screen a mutant of the gene vhb for vitreoscilla hemoglobin (Vhb) and insert into pTrc99A to transform the strains, to increase the microorganism's utilization ability for dissolved oxygen and increase the fermentation production the output of N-Acetyl-Glucosamine.

(697) 1. Escherichia coli strains of which the nagB promoter is replaced by a promoter with higher expression level and the glmS promoter is further deleted, and vhb and its mutants for expression of vitreoscilla hemoglobin (Vhb)

(698) (1) Amplify the vhb Gene and Insert into pTrc99A

(699) The nucleotide sequence the gene encoding vitreoscilla hemoglobin (Vhb) is SEQ ID No.60, and the amino acid sequence is SEQ ID No.61. Based on the preference cocon bases of Escherichia coli, optimize and synthesize the gene for vitreoscilla hemoglobin (Vhb), and load into pUC57 carrier. Obtain a carrier named as: vhb/pUC57.

(700) Primer Design: Forward primer (vhb-F) SEQ ID No.62, and reverse primer (vhb-R) SEQ ID No.63.

(701) Template: vhb/pUC57.

(702) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(703) Amplification Product Size: 441 bp.

(704) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(705) Digest enzymatically the obtained PCR amplification segment and carrier pTrc99A with Nco I and Hind III, separate by agarose gel electrophoresis, purify and recover vhb segment and pTrc99A segment, ligate overnight with T4 DNA ligase at 16° C., and carry out identification to obtain vhb/pTrc99A plasmid.

(706) (2) Escherichia coli strains of which the nagB promoter is transformed with vhb/pTrc99A and vhbM/pTrc99A to produce a promoter with higher expression level, and the glmS promoter is further deleted

(707) 1) Preparation of Competence

(708) {circle around (1)} Inoculate the bacterial suspension of AT-049 stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h.

(709) {circle around (2)} Add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min.

(710) {circle around (3)} Centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(711) 2) Plasmid Transformation

(712) {circle around (1)} Transfer 250 μL of spontaneously sedimentated thalli, add 5 μL of vhb/pTrc99A and vhbM/pTrc99A plasmids, respectively, and cultivate at −4° C. for 30 min.

(713) {circle around (2)} Heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h.

(714) {circle around (3)} Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate.

(715) {circle around (4)} Cultivate overnight (for 12-16 h) at 30° C.

(716) {circle around (5)} Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification.

(717) {circle around (6)} Positive clones are stored for use.

(718) No. of the obtained strains: AT-058 (AT-049, vhb/pTrc99A), and AT-059 (AT-049, vhbM/pTrc99A).

(719) 2. Escherichia coli strains of which the natural endogenous promoter of the glmS gene is replaced by Trc promoter, and the natural endogenous promoter of the nagB gene is deleted, and the gene vhb mutants for expression of vitreoscilla hemoglobin

(720) 1) Preparation of Competence

(721) {circle around (1)} Inoculate the bacterial suspension of AT-051 stored at −20° C. into 10 mL of LB broth medium in a ratio of 1:50-100, and shake-cultivate at 37° C. and 225 rpm for 2-3 h.

(722) {circle around (2)} Add the culture solution to a 10-mL centrifuge tube, centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL 0.1M CaCl.sub.2 on an ice bath for 5 min.

(723) {circle around (3)} Centrifugate at 4000 g×5 min, discard the supernatant, and suspend with 5 mL of 0.1M CaCl.sub.2 on an ice bath. Allow to stand at −4° C. for 12 h for spontaneous sedimentation.

(724) 2) Plasmid Transformation

(725) {circle around (1)} Transfer 250 μL of spontaneously sedimentated thalli, add 5 μL of vhb/pTrc99A and vhbM/pTrc99A plasmids, respectively, and cultivate at −4° C. for 30 min.

(726) {circle around (2)} Heat on a water bath at 42° C. for 1.5 min, add 0.7 mL of SOC medium, and shake at 30° C. for 2 h.

(727) {circle around (3)} Transfer 0.2 mL of the bacterial suspension, and smear on a penicillin plate.

(728) {circle around (4)} Cultivate overnight (for 12-16 h) at 30° C.

(729) {circle around (5)} Pick up monoclone, add 5 mL of LB broth medium and cultivate, and withdraw plasmid for identification.

(730) {circle around (6)} Positive clones are stored for use.

(731) No. of the obtained strains: AT-060 (AT-051, vhb/pTrc99A), and AT-061 (AT-051, vhbM/pTrc99A).

(732) 2. Escherichia coli strains integrated of which the natural endogenous promoter of glmS gene and nagB gene is replaced and/or deleted, and the gene vhb thereof and its mutant for expression of vitreoscilla hemoglobin (Vhb) as well as influence on the output of N-Acetyl-D-Glucosamine

(733) Carry out a shake-flask fermentation trial with the strains of which the natural endogenous promoter of glmS gene and nagB gene is replaced and/or deleted, and the strains AT-058, AT-059, AT-060, and AT-061 with the gene vhb thereof and its mutant for expression of vitreoscilla hemoglobin (Vhb). Transfer the monoclonal strain freshly cultivated in culture medium of the LB plate, inoculate into a test tube (13×150 mm) containing 3 mL of the LB broth culture medium, and shake-cultivate at 30° C. and 225 rpm for 8 h. Then transfer the seed culture solution, inoculate in 3% into a 250-mL shake-flask containing 50 mL of M9 culture solution. The initial OD.sub.600 is approximately 0.5; shake-cultivate at 37° C. and 225 rpm. The fermentation cycle is 72 h. At 24 h and 48 h, adjust to pH 7.0 with 10M NaOH. According to glucose consumption in the fermentation broth, add 65% glucose solution to maintain a glucose concentration of 20 g/L. After completion of fermentation, transfer 1 mL of the fermentation broth and centrifugate. Measure the content of N-Acetyl-D-Glucosamine by HPLC method.

(734) See Table 17 for the output from shake-flask fermentation by recombinant strains. The results show that: The output may be increased obviously from expression of vhb by the recombinant strains both with transformed vhb/pTrc99A and with transformed vhbM/pTrc99A plasmid; moreover, the output is increased more significant by the recombinant strain with transformed vhbM/pTrc99A plasmid.

(735) TABLE-US-00018 TABLE 17 Output from Shake-flask Fermentation by the Recombinant Strains for Expression of vhb and vhbM Output of N-Acetyl-D-Glucosamine species (g/L) AT-049(AT-048, ΔglmS promotor)  8.6 ± 0.9 AT-058 (AT-049, vhb/pTrc99A) 10.5 ± 1.0 AT-059 (AT-049, vhbM/pTrc99A) 13.5 ± 1.1 AT-051 (AT-050, ΔnagB promotor)  5.7 ± 0.5 AT-060 (AT-051, vhb/pTrc99A)  8.4 ± 0.6 AT-061 (AT-051, vhbM/pTrc99A) 11.7 ± 1.0

Example 6

(736) This implementation example describes Escherichia coli strains integrated with pTrc-nanKM gene cassette, of which the natural endogenous promoter of the nanE gene is replaced by Trc promoter, and the gene vhb thereof and its mutant for expression of vitreoscilla hemoglobin (Vhb) as well as influence on the output of N-Acetyl-D-Glucosamine.

(737) 1. The natural endogenous promoter with nanE gene of Escherichia coli strains integrated with pTrc-nanKM cassette is replaced with Trc promoter

(738) First, amplify Trc promoter sequence segment and fKanrf segment, and splice together. Then design homologous primers, and amplify linear DNA full-length segment for targeting of Red recombination.

(739) (1) Amplification of Trc promoter sequence

(740) According to public information, look up Trc promoter sequence: SEQ ID No.32.

(741) Primer Design: Forward primer (KanTrcRed-F) SEQ ID No.33, and reverse primer (KanTrcRed-R) SEQ ID No.34.

(742) Template: pTrc99A

(743) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(744) Product Size: 166 bp.

(745) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(746) (2) Amplify the kanamycin resistance gene with recognition sites (FRT sites) for FLP recombinase at its both ends: fKanrf

(747) Primer Design: Forward primer (mfKanf-F) SEQ ID No.1, and reverse primer (mfKanf-R) SEQ ID No.2.

(748) Template: pPic9K.

(749) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(750) fKanrf size: 1.28 kb. Its nucleotide sequence is SEQ ID No.3.

(751) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(752) (3) Amplification of fKanrf spliced with Trc promotor

(753) Primer Design: Forward primer (fKanfRed-F1) SEQ ID No.35, and reverse primer (fKanfRed-R1) SEQ ID No.36.

(754) Template: fKanrf.

(755) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(756) fKanrf size from secondary amplificatino: 1.3 kb.

(757) The PCR product is separated by 1% agarose gel electrophoresis, and purified to recover the segment.

(758) (4) Preparation of Linear DNA Full-length PCR Segment for Targeting of Red Recombination

(759) Design homologous primers: Based on promoter sequence SEQ ID No.37 of the nanE gene. Design primers to be replaced with Trc promoter: Forward primer (ProNanEpTrc-F) SEQ ID No.38, and reverse primer (ProNanEpTrc-R) SEQ ID No.39.

(760) Template: Mix Trc promoter PCR segment and fKanrf PCR segment from secondary amplification in the ratio of 1:1.

(761) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(762) Amplification Product: Homologous Arm+fKanrf+Trc Promoter+Homologous Arm.

(763) The PCR product is separated by agarose gel electrophoresis, and purified and recovered to obtain 100 ng/μL linear DNA full-length PCR segment for targeting of Red recombination.

(764) (5) Red Recombination Operation

(765) First, pKD46 carrier is introduced into the AT-007-02 strain of Escherichia coli. Then, the prepared linear DNA segment for targeting is electrotransformed, and positive clones are screened. Finally, the resistance gene is removed.

(766) No. of the obtained strain: AT-009 (AT-007-02, ΔnanE promotor::Trc promoter).

(767) 2. Escherichia coli strains integrated with pTrc-nanEM gene cassette, of which the natural endogenous promoter of the nanE gene is replaced by Trc promoter, and the gene vhb thereof and its mutant for expression of vitreoscilla hemoglobin (Vhb)

(768) First, prepare competence of recombinant Escherichia coli strain AT-009; then, transform vhb/pTrc99A and vhbM/pTrc99A plasmids into AT-009 by CaCl.sub.2 transformation method, pick up monoclones and cultivate, and pipet plasmid to identify positive clones. No. of the obtained strains: AT-062 (AT-009, vhb/pTrc99A), and AT-063 (AT-009, vhbM/pTrc99A).

(769) Carry out a shake-flask fermentation trial with the strains AT-062 and AT-063 with the gene vhb and its mutant for expression of vitreoscilla hemoglobin. See Table 18 for the output from shake-flask fermentation by recombinant strains. The results show that: The output may be increased obviously from expression of vhb by the recombinant strains both with transformed vhb/pTrc99A and with transformed vhbM/pTrc99A plasmid; moreover, the output is increased more significant by the recombinant strain with transformed vhbM/pTrc99A plasmid.

(770) TABLE-US-00019 TABLE 18 Output from Shake-flask Fermentation by the Recombinant Strain Output of N-Acetyl-D-Glucosamine species (g/L) AT-009 (AT-007-02, .sup.Δ nanE promoter::Trc 19.9 ± 1.5 promoter) (reference) AT-062 (AT-009, vhb/pTrc99A) 23.9 ± 1.4 AT-063 (AT-009, vhbM/pTrc99A) 26.8 ± 1.3

Example 7

(771) This implementation example describes Escherichia coli strains integrated with pTrc-nanKM and influences of those on the output of N-Acetyl-D-Glucosamine, of which the natural endogenous promoter of the gene glmS of Glucosamine-6-Phosphate Synthase (GlmS) and/or the nagB gene of D-Glucosamine-6-Phosphate Deaminase (NagB) is replaced and/or deleted, and the gene vhb and its mutants for expression of vitreoscilla hemoglobin (Vhb).

(772) In Escherichia coli strains integrated with pTrc-nanKM cassette, the natural endogenous promoter of the nanB gene is replaced by Trc promoter to produce AT-010 (AT-007-02, Δ nagB promotor::Trc promoter), and the natural endogenous promoter of the glmS gene is further deleted to produce AT-011 (AT-010, glmS promotor); In Escherichia coli strains integrated with pTrc-nanKM cassette, the natural endogenous promoter of the glmS gene is replaced by Trc promoter to produce AT-012 (AT-007-02, Δ nagB promotor::Trc promoter), and the natural endogenous promoter of the nagB gene is further deleted to produce AT-013 (AT-012, Δ nagB promotor).

(773) Prepare competence of recombinant Escherichia coli strain AT-11 and AT-013; then, transform vhb/pTrc99A and vhbM/pTrc99A plasmids into AT-011 and AT-013 by CaCl.sub.2 transformation method, pick up monoclones and cultivate, and pipet plasmid to identify positive clones.

(774) No. of the obtained strains: AT-064 (AT-011, vhb/pTrc99A), AT-065 (AT-011, vhbM/pTrc99A), AT-066 (AT-013, vhb/pTrc99A), and AT-067 (AT-013, vhbM/pTrc99A).

(775) Carry out a shake-flask fermentation trial with the strains AT-064, AT-065, AT-066, and AT-067 with the gene vhb and its mutant for expression of vitreoscilla hemoglobin. See Table 19 for the output from shake-flask fermentation by recombinant strains. The results show that: The output may be increased obviously from expression of vhb by the recombinant strains both with transformed vhb/pTrc99A and with transformed vhbM/pTrc99A plasmid; moreover, the output is increased more significant by the recombinant strain with transformed vhbM/pTrc99A plasmid.

(776) TABLE-US-00020 TABLE 19 Output from Shake-flask Fermentation by the Recombinant Strain Output of N-Acetyl-D-Glucosamine Species (g/L) AT-011 (AT-010, .sup.Δ glmS promotor) (reference) 21.6 ± 1.4 AT-064 (AT-011, vhb/pTrc99A) 24.8 ± 1.4 AT-065 (AT-011, vhbM/pTrc99A) 28.6 ± 1.5 AT-013 (AT-012, .sup.Δ nagB promotor) (reference) 21.3 ± 1.6 AT-066 (AT-013, vhb/pTrc99A) 24.6 ± 1.4 AT-067 (AT-013, vhbM/pTrc99A) 27.9 ± 1.3

Example 8

(777) This implementation example describes Escherichia coli strains integrated with pTrc-nanKM gene cassette, of which the natural endogenous promoter of the wecB gene is replaced by Trc promoter, and the gene vhb thereof and its mutant for expression of vitreoscilla hemoglobin (Vhb) as well as influence on the output of N-Acetyl-D-Glucosamine.

(778) 1. The natural endogenous promoter of the wecB gene of Escherichia coli strains integrated with pTrc-nanKM cassette is replaced by Trc promoter

(779) First, amplify Trc promoter sequence segment and fKanrf segment, and splice together. Then design homologous primers, and amplify linear DNA full-length segment for targeting of Red recombination.

(780) (1) Preparation of Linear DNA Full-length PCR Segment for Targeting of Red Recombination

(781) Design of Homologous Arm Primers: According to NCBI, look up NC_000913 to obtain the nucleotide sequence SEQ ID No.53 of the gene promoter of Escherichia coli UDP-N-AcetylGlucosamine-2-Epimerase (WecB), design homologous arm primers with the promoter replaced by Trc promoter: Forward primer (ProwecBpTrc-F) SEQ ID No.54, and reverse primer (Pro wecBpTrc-R) SEQ ID No.55.

(782) Template: Mix Trc promoter PCR segment and fKanrf PCR segment from secondary amplification in the ratio of 1:1.

(783) PCR reaction conditions: Step 1: Degenerate at 94° C. for 1 min; Step 2: Incubate at 94° C. for 30 s, at 55° C. for 30 s, and at 72° C. for 40 s, and carry out 30 cycles; Step 3: Extend at 72° C. for 10 min.

(784) Amplification Product: Homologous Arm+fKanrf+Trc Promoter+Homologous Arm. The PCR product is separated by agarose gel electrophoresis, and purified and recovered to obtain 100 ng/μL linear DNA full-length PCR segment for targeting of Red recombination.

(785) (2) Red Recombination Operation

(786) First, pKD46 carrier is introduced into the AT-007-02 strain of Escherichia coli. Then, the prepared linear DNA segment for targeting is electrotransformed, and positive clones are screened. Finally, the resistance gene is removed.

(787) No. of the obtained strain: AT-019(AT-007-02, Δ wecB promotor::Trc promoter).

(788) 2. Escherichia coli strains integrated with pTrc-nanEM gene cassette, of which the natural endogenous promoter of the wecB gene is replaced by Trc promoter, and the gene vhb thereof and its mutant for expression of vitreoscilla hemoglobin (Vhb)

(789) First, prepare competence of recombinant Escherichia coli strain AT-019; then, transform vhb/pTrc99A and vhbM/pTrc99A plasmids into AT-019 by CaCl.sub.2 transformation method, pick up monoclones and cultivate, and pipet plasmid to identify positive clones.

(790) No. of the obtained strains: AT-068 (AT-019, vhb/pTrc99A), and AT-069 (AT-019, vhbM/pTrc99A).

(791) Carry out a shake-flask fermentation trial with the strains AT-068 and AT-069 with the gene vhb and its mutant for expression of vitreoscilla hemoglobin. See Table 20 for the output from shake-flask fermentation by recombinant strains. The results show that: The output may be increased obviously from expression of vhb by the recombinant strains both with transformed vhb/pTrc99A and with transformed vhbM/pTrc99A plasmid; moreover, the output is increased more significant by the recombinant strain with transformed vhbM/pTrc99A plasmid.

(792) TABLE-US-00021 TABLE 20 Output from Shake-flask Fermentation by the Recombinant Strain Output of N-Acetyl-D-Glucosamine species (g/L) AT-019 (AT-007-02, .sup.Δ wecB promotor::Trc 23.0 ± 1.8 promoter) (reference) AT-068 (AT-019, vhb/pTrc99A) 27.2 ± 1.9 AT-069 (AT-019, vhbM/pTrc99A) 31.5 ± 2.0

Example 9

(793) This implementation example describes Escherichia coli strains integrated with pTrc-nanEM and influences of those on the output of N-Acetyl-D-Glucosamine, of which the natural endogenous promoter of the gene glmS of Glucosamine-6-Phosphate Synthase (GlmS) and/or the nagB gene of D-Glucosamine-6-Phosphate Deaminase (NagB) is replaced and/or deleted, and the gene vhb and its mutants for expression of vitreoscilla hemoglobin (Vhb).

(794) In Escherichia coli strains integrated with pTrc-nanEM cassette, the natural endogenous promoter of the nanB gene is replaced by Trc promoter to produce AT-032 (AT-031-02, Δ nagB promotor::Trc promoter), and the natural endogenous promoter of the glmS gene is further deleted to produce AT-033 (AT-032, Δ glmS promotor); In Escherichia coli strains integrated with pTrc-nanEM cassette, the natural endogenous promoter of the glmS gene is replaced by Trc promoter to produce AT-034 (AT-031-02, Δ nagB promotor::Trc promoter), and the natural endogenous promoter of the nagB gene is further deleted to produce AT-035 (AT-034, Δ nagB promotor).

(795) Prepare competence of recombinant Escherichia coli strain AT-033 and AT-035; then, transform vhb/pTrc99A and vhbM/pTrc99A plasmids into AT-033 and AT-035 by CaCl.sub.2 transformation method, pick up monoclones and cultivate, and pipet plasmid to identify positive clones.

(796) No. of the obtained strains: AT-070 (AT-033, vhb/pTrc99A), AT-071 (AT-033, vhbM/pTrc99A), AT-072 (AT-035, vhb/pTrc99A), and AT-073 (AT-035, vhbM/pTrc99A).

(797) Carry out a shake-flask fermentation trial with the strains AT-070, AT-071, AT-072, and AT-073 with the gene vhb and its mutant for expression of vitreoscilla hemoglobin. See Table 21 for the output from shake-flask fermentation by recombinant strains. The results show that: The output may be increased obviously from expression of vhb by the recombinant strains both with transformed vhb/pTrc99A and with transformed vhbM/pTrc99A plasmid; moreover, the output is increased more significant by the recombinant strain with transformed vhbM/pTrc99A plasmid.

(798) TABLE-US-00022 TABLE 21 Output from Shake-flask Fermentation by the Recombinant Strain Output of N-Acetyl-D-Glucosamine species (g/L) AT-033 (AT-032, .sup.Δ glmS promotor) (reference) 12.2 ± 1.2 AT-070 (AT-033, vhb/pTrc99A) 15.0 ± 1.2 AT-071 (AT-033, vhbM/pTrc99A) 18.1 ± 1.3 AT-035 (AT-034, .sup.Δ nagB promotor) (reference)  9.8 ± 0.8 AT-072 (AT-035, vhb/pTrc99A) 13.1 ± 1.2 AT-073 (AT-035, vhbM/pTrc99A) 16.7 ± 1.3

Example 10

(799) This implementation example describes Escherichia coli strains integrated with pTrc-nanEM gene cassette, of which the natural endogenous promoter of the wecB gene is replaced by Trc promoter, and the gene vhb thereof and its mutant for expression of vitreoscilla hemoglobin (Vhb) as well as influence on the output of N-Acetyl-D-Glucosamine.

(800) The natural endogenous promoter of the wecB gene of Escherichia coli strains integrated with pTrc-nanKM cassette is replaced by Trc promoter to produce AT-037 (AT-031-02, Δ wecB promotor::Trc promoter).

(801) Prepare competence of recombinant Escherichia coli strain AT-037; then, transform vhb/pTrc99A and vhbM/pTrc99A plasmids into AT-037 by CaCl.sub.2 transformation method, pick up monoclones and cultivate, and pipet plasmid to identify positive clones.

(802) No. of the obtained strains: AT-074 (AT-037, vhb/pTrc99A), and AT-075 (AT-037, vhbM/pTrc99A).

(803) Carry out a shake-flask fermentation trial with the strains AT-074 and AT-075 with the gene vhb and its mutant for expression of vitreoscilla hemoglobin. See Table 22 for the output from shake-flask fermentation by recombinant strains. The results show that: The output may be increased obviously from expression of vhb by the recombinant strains both with transformed vhb/pTrc99A and with transformed vhbM/pTrc99A plasmid; moreover, the output is increased more significant by the recombinant strain with transformed vhbM/pTrc99A plasmid.

(804) TABLE-US-00023 TABLE 22 Output from Shake-flask Fermentation by the Recombinant Strain Output of N-Acetyl-D-Glucosamine species (g/L) AT-037 (AT-031-02, .sup.Δ wecB promotor::Trc 13.4 ± 1.2 promoter) (reference) AT-074 (AT-037, vhb/pTrc99A) 16.2 ± 1.2 AT-075 (AT-037, vhbM/pTrc99A) 19.9 ± 1.3

Example 11

(805) This implementation example describes Escherichia coli strains integrated with pTrc-nanBM and influences of those on the output of N-Acetyl-D-Glucosamine, of which the natural endogenous promoter of the gene glmS of Glucosamine-6-Phosphate Synthase (GlmS) and/or the nagB gene of D-Glucosamine-6-Phosphate Deaminase (NagB) is replaced and/or deleted, and the gene vhb and its mutants for expression of vitreoscilla hemoglobin (Vhb).

(806) In Escherichia coli strains integrated with pTrc-nanBM cassette, the natural endogenous promoter of the nanB gene is replaced by Trc promoter to produce AT-044 (AT-043-02, Δ nagB promotor::Trc promoter), and the natural endogenous promoter of the glmS gene is further deleted to produce AT-045 (AT-044, Δ glmS promotor); In Escherichia coli strains integrated with pTrc-nanBM cassette, the natural endogenous promoter of the glmS gene is replaced by Trc promoter to produce AT-046 (AT-043-02, Δ nagB promotor::Trc promoter), and the natural endogenous promoter of the nagB gene is further deleted to produce AT-047 (AT-046, Δ nagB promotor).

(807) Prepare competence of recombinant Escherichia coli strain AT-045 and AT-047; then, transform vhb/pTrc99A and vhbM/pTrc99A plasmids into AT-045 and AT-047 by CaCl.sub.2 transformation method, pick up monoclones and cultivate, and pipet plasmid to identify positive clones.

(808) No. of the obtained strains: AT-076, AT-077, AT-078 (AT-047, vhb/pTrc99A), and AT-079.

(809) Carry out a shake-flask fermentation trial with the strains AT-076, AT-077, AT-078, and AT-079 with the gene vhb and its mutant for expression of vitreoscilla hemoglobin. See Table 23 for the output from shake-flask fermentation by recombinant strains. The results show that: The output may be increased obviously from expression of vhb by the recombinant strains both with transformed vhb/pTrc99A and with transformed vhbM/pTrc99A plasmid; moreover, the output is increased more significant by the recombinant strain with transformed vhbM/pTrc99A plasmid.

(810) TABLE-US-00024 TABLE 23 Output from Shake-flask Fermentation by the Recombinant Strain Output of N-Acetyl-D-Glucosamine species (g/L) AT-045 (AT-044, .sup.Δ glmS promotor) (reference) 19.2 ± 1.2 AT-076 (AT-045, vhb/pTrc99A) 23.0 ± 1.3 AT-077 (AT-045, vhbM/pTrc99A) 28.1 ± 1.5 AT-047 (AT-046, .sup.Δ nagB promotor) (reference) 15.5 ± 1.2 AT-078 (AT-047, vhb/pTrc99A) 20.6 ± 1.3 AT-079 (AT-047, vhbM/pTrc99A) 25.6 ± 1.4

Example 12

(811) This implementation example describes Escherichia coli strains integrated with pTrc-nanKM gene cassette, of which the natural endogenous promoter of the nanE gene is replaced by Trc promoter, the natural endogenous promoter of the wecB gene and NagB gene is replaced and/or deleted, the natural endogenous promoter of the wecB gene is replaced by Trc promoter, and the gene vhb thereof and its mutant for expression of vitreoscilla hemoglobin (Vhb) as well as influence on the output of N-Acetyl-D-Glucosamine.

(812) In Escherichia coli strains integrated with pTrc-nanKM cassette, of which the natural endogenous promoter of the nagB gene is replaced by Trc promoter and meanwhile the natural endogenous promoter of the glmS gene is deleted, the natural endogenous promoter of the nanE gene is replaced by Trc promoter to produce AT-015 (AT-011,Δ nanE promotor::Trc promoter), and the natural endogenous promoter of the wecB gene is further replaced by Trc promoter to produce AT-027 (AT-015, Δ wecB promotor::Trc promoter); In Escherichia coli strains integrated with pTrc-nanKM cassette, of which the natural endogenous promoter of the glmS gene is replaced by Trc promoter and meanwhile the natural endogenous promoter of the nagB gene is deleted, the natural endogenous promoter of the nanE gene is replaced by Trc promoter to produce AT-017 (AT-013, Δ nanE promotor::Trc promoter), and the natural endogenous promoter of the wecB gene is further replaced by Trc promoter to produce AT-029 (AT-017, Δ wecB promotor::Trc promoter);

(813) Prepare competence of recombinant Escherichia coli strain AT-027 and AT-029; then, transform vhb/pTrc99A and vhbM/pTrc99A plasmids into AT-027 and AT-029 by CaCl.sub.2 transformation method, pick up monoclones and cultivate, and pipet plasmid to identify positive clones.

(814) No. of the obtained strains: AT-080 (AT-027, vhb/pTrc99A), AT-081 (AT-027, vhbM/pTrc99A), AT-082 (AT-029, vhb/pTrc99A), and AT-083 (AT-029, vhbM/pTrc99A).

(815) Carry out a shake-flask fermentation trial with the strains AT-080, AT-081, AT-082, and AT-083 with the gene vhb and its mutant for expression of vitreoscilla hemoglobin. See Table 24 for the output from shake-flask fermentation by recombinant strains. The results show that: The output may be increased obviously from expression of vhb by the recombinant strains both with transformed vhb/pTrc99A and with transformed vhbM/pTrc99A plasmid; moreover, the output is increased more significant by the recombinant strain with transformed vhbM/pTrc99A plasmid.

(816) TABLE-US-00025 TABLE 24 Output from Shake-flask Fermentation by the Recombinant Strain Output of N-Acetyl-D-Glucosamine species (g/L) AT-027 (AT-015, .sup.Δ wecB promotor::Trc 39.8 ± 2.0 promoter) (reference) AT-080 (AT-027, vhb/pTrc99A) 46.5 ± 2.1 AT-081 (AT-027, vhbM/pTrc99A) 49.5 ± 2.0 AT-029 (AT-017, .sup.Δ wecB promotor::Trc 40.2 ± 2.1 promoter) (reference) AT-082 (AT-035, vhb/pTrc99A) 47.7 ± 2.2 AT-083 (AT-035, vhbM/pTrc99A) 51.6 ± 2.3

Example 13

(817) This implementation example describes a fermentation trial for production of N-Acetyl-D-Glucosamine by 10-L fermentation tank.

(818) Carry a fermentation trial for production of N-Acetyl-D-Glucosamine by 10-L fermentation tank, using recombinant engineering strain AT-083 as production strain.

(819) 1. Seed Cultivation

(820) (1) Cultivation of Primary Seed: Pick monoclonal strain freshly cultivated in the LB plate medium, inoculate into 8 mL of LB broth medium, and shake-cultivate at 37° C. and 225 rpm for 8 h.

(821) (2) Cultivation of Secondary Seed: Transfer 6 mL of the primary seed culture solution, inoculate into 1000-mL shake flask containing 200 mL of M9 culture solution, and shake-cultivate at 37° C. and 225 rpm for 16 h, until OD.sub.600 value is 6.0-10, approximately the medium stage of log growth.

(822) (3) Prepare the fermentation medium according to Table 25, where the microelement solution is prepared according to Table 26, and the complex vitamins solution is prepared according to Table 27.

(823) TABLE-US-00026 TABLE 25 Fermentation Medium Amount Ingredients (/L) K.sub.2HPO.sub.4 1.30 g KH.sub.2PO.sub.4 1.00 g MgSO.sub.4•7H.sub.2O 0.10 g NH.sub.4Cl 0.02 g (NH.sub.4).sub.2SO.sub.4 0.20 g NaH.sub.2PO.sub.4 0.60 g Polyether Defoamer 10 mL Microelement Solution 4 ml Complex Vitamins Solution 4 ml Glucose 6.00 g
NOTE:

(824) {circle around (1)} The microelement solution is sterilized separately and then added, and the vitamins solution is filtered and then added;

(825) {circle around (2)} Glucose: Concentration 65% (w/v); it is sterilized separately and is added prior to inoculation. Amount to be added: 6.0 g/L;

(826) {circle around (3)} The above solutions are combined, and then adjust to pH 7.0 with 10 M NH.sub.4OH;

(827) {circle around (4)} The fermentation medium is basal medium prior to addition of glucose; initial loading amount of the basal medium (initial volume accounting for the total capacity of the fermentation tank): 50%.

(828) TABLE-US-00027 TABLE 26 Microelement Solution Amount used Ingredients (g/L) CaCl.sub.2•2H.sub.2O 10 FeCl.sub.3•6H.sub.2O 10 MnSO.sub.4•5H.sub.2O 2.5 AlCl.sub.3•6H.sub.2O 2.5 CoCl.sub.2•6H.sub.2O 1.75 ZnSO.sub.4•2H.sub.2O 0.5 NaMoO.sub.4•2H.sub.2O 0.5 CuSO.sub.4•5H.sub.2O 0.25 H.sub.3BO.sub.3 0.125 pH 3-4

(829) TABLE-US-00028 TABLE 27 Complex Vitamins Solution Amount Ingredients (mg/L) Folic Acid 2 Vitamin B.sub.2 100 Riboflavin Vitamin B.sub.1 1500 Thiamine HCl Nicotinic Acid 500 Vitamin B6 500 Pyridoxine HCl Calcium Pantothenate, 500 Ca-panthothenate Biotin 1 Vitamin B.sub.12 10

(830) 2. Inoculation

(831) Inoculate the secondary seed solution to the fermentation tank in the ratio of 40 mL/L; inoculation size: 2.5-5% (v/v); the initial OD.sub.600 is 0.3-0.5.

(832) 3. process parameters

(833) Carry out a high-density fermentation by 10-L self-control fermentation tank, and collect data by software equipped in the machine to realize online control by computer. The control parameters are: The air flow is 0.5-1 vvm.; dissolved oxygen is >=20%, to increase regulation of rotational speed and ventilation; temperature 37° C.; pH 7.0, the automatic flow is maintained stable by addition of saturated ammonia water. Supplement glucose when glucose in the basal medium is consumed up, i.e. dissolved oxygen is risen again. Glucose is supplemented in a speed to control residual glucose concentration is not more than 0.45 g/L. The glucose-supplementing solution contains 65% (w/v) of glucose, is added with 2.5% Sodium Gluconate or 6% Ribose. The fermentation is stopped after 60-72 h. Total loading amount: 75%-80%.

(834) 4. Example (10-L fermentation tank) (1) Strain No.: AT-083. Batch No.: 1019. (2) Concentration of Seed Solution: OD.sub.600 2.8. (3) Base Stock: 4 L. (4) Inoculation Size 200 mL. (5) Glucose supplementation speed: The residual glucose concentration is controlled as not more than 0.45 g/L. (6) Glucose-supplementing solution: The solution contains glucose in a concentration of 65% (w/v) and is added with 2.5% sodium gluconate. (7) Track Indicators: Measure OD.sub.600 and residual glucose content (residual glucose in the fermentation solution). (8) Product: N-Acetyl-D-Glucosamine. Potency: 72 h, 156 g/L.

Example 14

(835) This implementation example describes the processing process after separation and purification of N-Acetyl-D-Glucosamine and D-Glucosamine Hydrochloride

(836) 1. Refinement of N-Acetyl-D-Glucosamine

(837) (1) Deactivation: The fermentation solution is placed at 80° C. for 30 min.

(838) (2) Solid-liquid separation: Centrifugate at 4000-8000 rpm, discard the bacterial residue and proteins, and transfer the fermentation solution. It may also be filtered via ceramic membrane.

(839) (3) Decoloration: Product:Water:Activated Charcoal=1:(1.5-3):(0.01-0.1); stir for 0.5-5 h.

(840) (4) Desalt: Desalt by electroosmosis. Initial salt concentration of the fermentation loaded into the concentrated chamber tank: 0.01-0.05 mol/L. Flow rate of the dilute-chamber fermentation solution: 40-80 L/h; flow rate of the concentrated-chamber fermentation solution: 40-80 L/h; the voltage of single membrane pair is 0.5-1.4 V. It may also be desalted by anion or cation ion exchange resin.

(841) (5) Concentration: The fermentation solution desalted is heated at 50-80° C. under vacuum conditions (0.095 MPa) for 8-15 h until oversaturation, by approximately 4-6 folds.

(842) (6) Concentration: The concentrated fermentation solution is cooled to 25-35° C. in water at 25° C., then cooled for 1-3 h to 0-10° C. in water at 0° C. Add anhydrous alcohol (in an amount of approximately 5-20 times the product weight), and stir at 700-1500 rpm for 15 min-1 h.

(843) (7) Washing: Add anhydrous alcohol (same amount as that of the product) and stir for 10-100 rpm, 0.5-2 h.

(844) (8) Drying: 50-100° C., 3-10 h. Purity: 99.96%. The total yield is 91.5%.

(845) 2. Refinement of D-Glucosamine Hydrochloride

(846) (1) Deactivation: The fermentation solution is placed at 80° C. for 30 min.

(847) (2) Solid-liquid separation: Centrifugate at 4000-8000 rpm, discard the bacterial residue and proteins, and transfer the fermentation solution. It may also be filtered via ceramic membrane.

(848) (3) Decoloration: Product:Water:Activated Charcoal=1:(1.5-3):(0.01-0.1); stir for 0.5-5 h.

(849) (4) Desalt: Desalt by electroosmosis. Initial salt concentration of the fermentation loaded into the concentrated chamber tank: 0.01-0.05 mol/L. Flow rate of the dilute-chamber fermentation solution: 40-80 L/h; flow rate of the concentrated-chamber fermentation solution: 40-80 L/h; the voltage of single membrane pair is 0.5-1.4 V. It may also be desalted by anion or cation ion exchange resin.

(850) (5) Concentration: The fermentation solution desalted is heated at 50-80° C. under vacuum conditions (0.095 MPa) for 8-15 h until oversaturation, by approximately 4-6 folds.

(851) (6) Hydrolysis: Introduce the concentrated fermentation solution to an enamel or glass container, add concentrated hydrochloric acid (37%) to a final concentration of 12%-16%, stir thoroughly, and maintain at 70° C. for 90 min. Hydrochloric Acid may be used in a recycling way.

(852) (7) Crystalliation: First cool to 25-35° C. in water at 25° C., and then cool to 4° C. in water at 0° C. for 1-3 h.

(853) (8) Washing: Add anhydrous alcohol (same amount as that of the product) and stir for 10-100 rpm, 0.5-2 h. Centrifugate at 700-1500 rpm for 15-60 min to obtain Glucosamine Hydrochloride; the conversion rate is 89.5%.

(854) (9) Dissolution: Dissolve the washed product in water in an similar volume to that of the original fermentation solution.

(855) (10) Decoloration: Add activated charcoal (in an amount of 1%). Mix for 30 min. Then centrifugate at 700-1500 rpm for 15-60 min. Or filter to obtain a colorless filtrate.

(856) (11) Recrystalliation: Evaporate at 50° C. and 55 cmHg vacuum until oversaturation. Add anhydrous alcohol (in an amount of approximately 5-20 times the product weight), and stir at 700-1500 rpm for 15 min-1 h.

(857) (12) Washing: Add anhydrous alcohol (same amount as that of the product) and stir for 10-100 rpm, 0.5-2 h. Then centrifugate at 700-1500 rpm for 15-60 min.

(858) (13) Drying: 50-100° C., 3-10 h. Purity: 99.92%. The total yield is 84.6%.

(859) Although this Invention is described detailedly by common explanations and specific implementation schemes, it may be revised or improved on top of this Invention; this point is as plain as the nose on your face for a technician in this field. Therefore, such revisions or improvements that are not deviated from the spirits of this Invention still fall in the range under protection required by this Invention.