Method for separation and purification of n-acetylglucosamine

Abstract

The disclosure relates to a method for separation and purification of N-acetyl-glucosamine, and belongs to the technical field of biological engineering. In the disclosure, a raw material solution containing N-acetyl-glucosamine is obtained by microbial fermentation or by hydrolyzing the chitin. The raw material solution is subjected to flocculation pretreatment, and continuous centrifugation or pressure filtration is performed to remove suspended solids such as microorganisms, proteins and polysaccharides to obtain clear liquid. Double-stage ion exchange chromatography is performed to remove impurities such as charged organic molecules and inorganic salts. Membrane concentration is performed to efficiently remove water to improve the concentration of the target product. Spray drying or further evaporation concentration and crystallization are performed. Finally drying is performed to obtain an N-acetyl-glucosamine crystal of which the purity is more than 99%.

Claims

1. A method for preparing N-acetyl-glucosamine, wherein the N-acetyl-glucosamine is prepared by taking a solution containing N-acetyl-glucosamine as a raw material solution according to the following steps: (1) adding flocculants to the raw material solution containing N-acetyl-glucosamine for flocculation, wherein the flocculants are food safety grade and used either as single component or in combination of two or more selected components from polyacrylamide, dimethylamine-epichlorohydrin copolymer, polyferric chloride, ferric chloride, ferric sulfate and ferrous sulfate; (2) performing solid-liquid separation on the solution after the flocculation in step (1) to obtain clear liquid and solid waste; (3) performing ion exchange chromatography on the clear liquid after the solid-liquid separation in step (2), wherein the ion exchange chromatography comprises double-stages column system of a cation column-anion column system or an anion column-cation column system in a device; and the form of the double-stages column system is an ion exchange fixed bed or an ion exchange simulated moving bed or an ion exchange continuous moving bed; (4) concentrating the solution after the ion exchange chromatography in step (3) to obtain a high-purity N-acetyl-glucosamine liquid product with a concentration of 20-50%; then, drying the product after the concentration, wherein the concentration treatment uses a reverse osmosis membrane or a nanofiltration membrane, the pore size of the nanofiltration membrane is 0.5-2 nm, and the molecular weight cut-off of the reverse osmosis membrane is 50-100 Da.

2. The method according to claim 1, wherein the raw material solution is a solution containing N-acetyl-glucosamine obtained by microbial fermentation or by hydrolyzing chitin; and the hydrolysis method comprises enzymatic hydrolysis or chemical hydrolysis.

3. The method according to claim 1, wherein the performing ion exchange chromatography comprises using ion exchange resin and adsorbing one or more impurities in the solution containing N-acetyl-glucosamine.

4. The method according to claim 3, wherein the adding mode of the flocculant in step (1) is (a) or (b): (a) a flocculant with a single component is added according to the following doses: the addition of the polyacrylamide is 0.01-0.3% of the dry weight of the biomass in the raw material, the addition of the dimethylamine-epichlorohydrin copolymer is 0.01-0.2% of the dry weight of the biomass, the addition of the polyferric chloride is 0.1-1.0% of the dry weight of the biomass, the addition of the ferric chloride is 0.1-0.9% of the dry weight of the biomass, the addition of the ferric sulfate is 0.1-1.0% of the dry weight of the biomass, and the addition of the ferrous sulfate is 0.2-2.0% of the dry weight of the biomass; (b) when a flocculant with two or more components is added, the addition of each component in the flocculant is 20-50% of the addition of the single component according to (a).

5. The method according to claim 1, wherein the solid-liquid separation in step (2) uses a device for plate and frame pressure filtration or continuous centrifugation; the device for plate and frame pressure filtration is a box type plate and frame filter press or a diaphragm type filter press; and the device for continuous centrifugation is a disc centrifuge.

6. The method according to claim 5, wherein a filter aid is added before the pressure filtration operation; the filter aid is any one or a combination of two or more selected from diatomite, attapulgite, perlite and powdered activated carbon; and the total addition of the filter aid is 0.5-5% of the raw material solution.

7. The method according to claim 5, wherein the solid-liquid separation in step (2) uses a device for plate and frame pressure filtration or continuous centrifugation; the device for plate and frame pressure filtration is a box type plate and frame filter press or a diaphragm type filter press; and the device for continuous centrifugation is a disc centrifuge.

8. The method according to claim 1, wherein a filler of a cation column or an anion column is acidic cation exchange resin or basic anion exchange resin; and the treatment temperature of the ion exchange chromatography is 5-40° C., the feed flow rate is 2.0-10.0 BV/h, and the flow rate of eluents is 1.0-8.0 BV/h.

9. The method according to claim 1, wherein the drying in step (4) is (a) or (b): (a) spray drying, vacuum low temperature drying or flash drying is performed; the inlet air temperature of the spray drying is 150-300° C.; the temperature of the vacuum low temperature drying is 40-80° C., and the vacuum degree is 70-95 kPa; and the inlet air temperature of the flash drying is 150-300° C.; (b) evaporation treatment and crystallization are performed subsequently, then the crystallized substance is dried; the evaporation is single-effect evaporation, double-effect evaporation or multiple effect evaporation; and the temperature of the crystallization is 5-40° C.

Description

BRIEF DESCRIPTION OF FIGURES

(1) FIG. 1 shows extraction process routes of N-acetyl-glucosamine.

DETAILED DESCRIPTION

Technical Term

(2) Eluate: the liquid solution that results from the ion exchange chromatography and contains the components which not be absorbed by the resin in the raw material solution. It is washed out with deionized water in the ion exchange process.

Example 1

(3) N-acetyl-glucosamine was prepared according to branch A and branch C of the process routes in FIG. 1, and specific steps were:

(4) (1) 50 m.sup.3 of N-acetyl-glucosamine fermentation broth with a concentration of 50 kg/m.sup.3 obtained by aerobic fermentation was collected in a fermentation broth storage tank. 20 L of a ferric sulfate solution with a concentration of 100 g/L and 25 L of a food-grade polyacrylamide solution with a concentration of 10 g/L were pumped into the fermentation broth storage tank. Stirring and mixing were performed completely, and then, flocculation was performed for 20 min.

(5) (2) The solution after the flocculation in step (1) was continuously pumped into a disc centrifuge with a rotation speed of 12000 rpm. The collected clear liquid flowed into a clear liquid tank, and the precipitate was collected into a temporary storage tank.

(6) (3) The clear liquid obtained in step (2) was sequentially pumped into an ion exchange column 1 #and an ion exchange column 2 #. The fillers in the ion exchange column 1 #and the ion exchange column 2 #were acidic cation exchange resin and basic anion exchange resin, respectively. The filler may also be basic anion exchange resin and acidic cation exchange resin, respectively. The flow rate was 4.0 BV/h, the eluate of the ion exchange column 2 #was collected into the storage tank, then the ion exchange column 1 #and the ion exchange column 2 #were washed with deionized water. The aforementioned eluates were all collected into the storage tank. The storage tank was configured to collect the eluate, and was used as a raw material solution storage tank for membrane concentration. A total of 51 m.sup.3 of eluate with an N-acetyl-glucosamine concentration of 46 kg/m.sup.3 was collected in the storage tank.

(7) Optionally, according to the adsorption capacity of the resins in the columns, an HCl solution with a concentration of 1.0 mol/L and an NaOH solution with a concentration of 1.0 mol/L were flowed into the cation column and the anion column respectively so as to regenerate the ion exchange columns. The ion exchange columns were washed with deionized water to neutral pH, so that the ion exchange columns were in a standby state;

(8) (4) The liquid in the storage tank collected in step (3), was pumped into a reverse osmosis membrane device and concentrated. The molecular weight cut-off of the reverse osmosis membrane was 50-100 Da and the operating pressure was 4-10 atm. 16.5 m.sup.3 of a concentrated solution with an N-acetyl-glucosamine concentration of 138 g/L was obtained after the concentration.

(9) Optionally, the liquid collected in step (3) may also directly enter step (5) to be subjected to spray drying; and

(10) (5) the concentrated solution obtained in step (4) was subjected to spray drying. The inlet air temperature of the spray drying was 190° C., the feed flow rate was 2 m.sup.3/h, and 2230 kg of N-acetyl-glucosamine powder was obtained after drying. The purity of the N-acetyl-glucosamine powder was 99.2%, and the overall recovery ratio was 89.2%.

Example 2

(11) N-acetyl-glucosamine was prepared according to branch B and branch C of process routes in FIG. 1, and specific steps were:

(12) (1) 50 m.sup.3 of N-acetyl-glucosamine fermentation broth with a concentration of 50 kg/m.sup.3 obtained by aerobic fermentation was collected in a fermentation broth storage tank. 20 L of a ferric chloride solution with a concentration of 100 g/L and 25 L of a food-grade polyacrylamide solution with a concentration of 10 g/L were pumped into the fermentation broth storage tank. 500 kg of diatomite was added, stirring and mixing were performed, and then, flocculation was performed for 20 min.

(13) (2) The solution after the flocculation in step (1) was pumped into a plate and frame filter press, when the pressure filtration was about to finish, 2 m.sup.3 of purified water was pumped in to wash the solid waste (filter cake) to obtain 50.2 m.sup.3 of filtrate with an N-acetyl-glucosamine concentration of 49 kg/m.sup.3, and the filtrate was collected into a clear liquid tank.

(14) (3) The clear liquid in the clear liquid tank in step (2) was continuously pumped into a cation column of a simulated moving bed system of which the filler was strong acidic styrene type cation resin (001×7). The resulting eluate from the cation column was continuously pumped into an anion column of the simulated moving bed system of which the filler was strong basic styrene type anion resin (201×7). The flow rate was 5.5 BV/h; a total of 53 m.sup.3 of eluate with an N-acetyl-glucosamine concentration of 45.7 kg/m.sup.3 was collected into the storage tank. If the ion exchange resin had been adsorbed to saturation, flowed into an HCl solution with a concentration of 1.0 mol/L and an NaOH solution with a concentration of 1.0 mol/L continuously to regenerate the ion exchange columns. The ion exchange resins were then continuously washed with deionized water to neutral pH.

(15) (4) The eluate liquid in the storage tank in step (3) was pumped into a reverse osmosis membrane device and concentrated. The molecular weight cut-off of the reverse osmosis membrane was 50-100 Da, and the operating pressure was 4-10 atm. 16.7 m.sup.3 of a concentrated solution was obtained after the concentration, and the N-acetyl-glucosamine concentration in the concentrated solution was 142 g/.

(16) (5) The concentrated solution in step (4) was subjected to spray drying. The inlet air temperature of the spray drying was 150° C., the feed flow rate was 2 m.sup.3/h, and 2380 kg of N-acetyl-glucosamine powder was obtained after drying. The purity of the N-acetyl-glucosamine powder was 99.1%, and the overall recovery rate was 95.2%.

Example 3

(17) The concentrated solution obtained in step (4) in Example 2 was treated according to a process route of a branch D in FIG. 1, and specific steps were:

(18) (a) The solution of 142 g/L N-acetyl-glucosamine was pumped into a triple-effect evaporation device, and operating conditions were: the flow rate was 4 m.sup.3/h, the pressure of heating steam was 0.7 MPa, the vacuum degree of a triple-effect condenser was 90 kPa, the inlet temperature of cooling water was 8-15° C., and the concentration of the output product was 710 g/L.

(19) (b) The output product in step (a) flowed into a crystallizer, and the crystallization temperature was controlled at 10° C. by jacket cooling.

(20) (c) The crystal suspension resulted from the step (b) flowed into a centrifuge for solid-liquid separation; and

(21) (d) The mother liquor separated in step (c) was subjected to decolorization with an activated carbon column, and then, the decolorized mother liquor was returned into the storage tank before the triple-effect evaporation device. The crystal slurry obtained by centrifugation was conveyed into a flash dryer through a screw conveyer, the inlet air temperature of the flash drying was 180° C., the outlet air temperature of the flash drying was 80° C., and 2350 kg of an N-acetyl-glucosamine crystal was obtained. The purity of the N-acetyl-glucosamine powder was 99.5%, and the overall recovery rate was 94.0%.

Example 4

(22) N-acetyl-glucosamine was prepared according to the branch B and branch C of process routes in FIG. 1, and specific steps were:

(23) (1) 230 m.sup.3 of N-acetyl-glucosamine fermentation broth with a concentration of 110 g/L obtained by aerobic fermentation was collected in a fermentation broth storage tank. 100 L of a ferric sulfate solution with a concentration of 100 g/L and 100 L of a food-grade polyacrylamide solution with a concentration of 10 g/L were pumped into the fermentation broth storage tank. 1500 kg of attapulgite and 500 kg of powdered activated carbon were added. Agitation was performed for 20 min for uniformly mixing, and then, flocculation and decolorization were performed.

(24) (2) The solution after the flocculation and decolorization in step (1) was pumped into a plate and frame filter press, the filtered initial liquid was returned to the fermentation broth storage tank. After the filtrate became clear, the obtained filtrate was collected into a clear liquid tank, and the water content of the obtained solid waste (filter cake) was about 62%.

(25) (3) the clear liquid obtained by filtration in step (2) was continuously pumped into an ion exchange column 1 #(anion resin) of a simulated moving bed system, the eluate of the ion exchange column 1 #continuously flows into an ion exchange column 2 #(cation resin) of the simulated moving bed system. The feed flow rate of both the ion exchange column 1 #and the ion exchange column 2 #was 5.0 BV/h. The eluate of the ion exchange column 2 #was collected into the storage tank before the membrane concentration device. If the ion exchange resin was saturated, an HCl solution with a concentration of 1.0 mol/L and an NaOH solution with a concentration of 1.0 mol/L were respectively used to continuously regenerate the cation resin and the anion resin. The ion exchange columns were continuously washed with deionized water to neutral pH. The simulated moving bed performed automatic feeding, elution and regeneration of fillers of the columns. The filler of the anion column was strongly basic styrene type anion exchange resin (201×7), and the filler of the cation column was strongly acidic styrene type cation exchange resin (001×7).

(26) (4) The liquid in the storage tank in step (3) was pumped into a ceramic nanofiltration membrane device and concentrated. The pore size of the ceramic nanofiltration membrane was 1 nm, and the operating pressure was 1.0-1.5 MPa. The N-acetyl-glucosamine concentration in 100 m.sup.3 of a concentrated solution after the concentration was 140 g/L.

(27) (5) The concentrated solution in step (4) was subjected to spray drying. The inlet air temperature of the spray drying was 200° C., and the feed flow rate was 2 m.sup.3/h. 24.2 tons of N-acetyl-glucosamine powder was obtained after drying. The purity of the N-acetyl-glucosamine powder was 99.2%, and the overall recovery rate was 95.6%.

Example 5

(28) On the basis of steps (1) to (4) in Example 4, N-acetyl-glucosamine was prepared according to the branch D of process routes in FIG. 1, and specific steps were:

(29) (a) 100 m.sup.3 of the concentrated N-acetyl-glucosamine solution with a concentration of 140 g/L after the nanofiltration membrane device in step (4) in Example 4 was pumped into a triple-effect evaporation device. The operating conditions were: the feed flow rate was 8 m.sup.3/h, the pressure of heating steam was 0.7 MPa, the vacuum degree of the third condenser of the triple-effect evaporation was 90 kPa. The inlet temperature of cooling water was 8-15° C., and the concentration of the output product was 700 g/L;

(30) (b) the output product in step (a) was conveyed to a crystallizer, and the crystallization temperature was controlled at 20° C. by jacket cooling of the crystallizer.

(31) (c) A suspension produced by crystallization of the crystallizer in step (b) was separated in a centrifuge, the crystallized mother liquor was conveyed into an activated carbon column for decolorization. The operating temperature was 25° C., the flow rate was 2.0 m.sup.3/h, and the crystallized mother liquor after the decolorization was returned into the storage tank in front of the triple-effect evaporation device. The crystal slurry obtained by centrifugation was conveyed into a flash dryer through a screw conveyer. The air inlet temperature of the flash drying was 180° C., the outlet air temperature of the flash drying was 80° C., and 23.8 tons of an N-acetyl-glucosamine crystal was obtained. The purity of the N-acetyl-glucosamine powder was 99.5%, and the overall recovery rate was 94.1%.

Example 6

(32) N-acetyl-glucosamine was prepared according to the branch A and branch C of the process routes in FIG. 1, and specific steps were:

(33) (1) 50 m.sup.3 of N-acetyl-glucosamine fermentation broth with a concentration of 50 kg/m.sup.3 obtained by aerobic fermentation was collected in a fermentation broth storage tank. 20 L of a food-grade dimethylamine-epichlorohydrin copolymer solution with a concentration of 1.0% (w) and 18 L of a food-grade ferric chloride solution with a concentration of 10% were pumped into the fermentation broth storage tank. Stirring and mixing were performed completely, and then, flocculation was performed for 20 min.

(34) (2) The solution after the flocculation in step (1) was pumped into a disc centrifuge with a rotation speed of 12000 rpm. 48.5 m.sup.3 of clear liquid with an N-acetyl-glucosamine concentration of 50 kg/m.sup.3 was collected into a clear liquid tank. The solid waste was collected into a temporary storage tank.

(35) (3) the clear liquid collected in step (2) was continuously pumped into a cation column of a continuous moving ion exchange bed of which the filler was strongly acidic styrene type cation exchange resin (001×7) and an anion column of the continuous moving ion exchange bed of which the filler was strongly basic styrene type anion exchange resin (201×7) sequentially. The flow rate of the both columns was 2.5 BV/h, the cation column and the anion column were washed with deionized water, and 55 m.sup.3 of eluate with an N-acetyl-glucosamine concentration of 43 kg/m.sup.3 was collected. The eluate flowed into a storage tank in front of a reverse osmosis membrane device. HCl solution with a concentration of 1.0 mol/L and NaOH solution with a concentration of 1.0 mol/L were used to regenerate the cation column and the anion column respectively in the continuous moving ion exchange bed. Then, the ion exchange columns were washed with deionized water to neutral pH, and the ion exchange columns were in a standby state. The material consumption for extracting acetyl-glucosamine using various ion exchange procedures was shown in Table 1.

(36) (4) The eluate collected in the storage tank in step (3) was directly subjected to spray drying. The inlet air temperature of the spray drying was 140° C., and the feed flow rate was 2 m.sup.3/h. 2295 kg of N-acetyl-glucosamine powder was obtained after drying. The purity of the N-acetyl-glucosamine powder was 99.3%, and the overall recovery rate was 91.8%.

Example 7

(37) N-acetyl-glucosamine was prepared according to process routes in FIG. 1, and specific steps were:

(38) (1) a solution containing N-acetyl-glucosamine was taken as a raw material, and a flocculant was added. The solution might be obtained by microbial fermentation, or obtained by enzymatic hydrolysis of biological raw materials containing chitin, or obtained by chemical hydrolysis of raw materials containing chitin.

(39) The flocculant was an organic flocculant with food safety, might also be an inorganic flocculant with food safety, and was selected from one of polyacrylamide, dimethylamine-epichlorohydrin copolymer, polyferric chloride, ferric chloride, ferric sulfate and ferrous sulfate.

(40) The additions of the flocculant were specifically as follows: the addition of the polyacrylamide was 0.01-0.3% of the dry weight of the biomass in the raw material. The addition of the dimethylamine-epichlorohydrin copolymer was 0.01-0.2% of the dry weight of the biomass. The addition of the polyferric chloride was 0.1-1.0% of the dry weight of the biomass. The addition of the ferric chloride was 0.1-0.9% of the dry weight of the biomass. The addition of the ferric sulfate was 0.1-1.0% of the dry weight of the biomass, and the addition of the ferrous sulfate was 0.2-2.0% of the dry weight of the biomass.

(41) (2) The solution after the flocculation in step (1) was operated through plate and frame pressure filtration or continuous centrifugation. The plate and frame pressure filtration might be performed by a box type plate and frame filter press or a diaphragm type filter press. The continuous centrifugation might be performed by a disc centrifuge.

(42) The filter residues after solid-liquid separation were used to prepare fertilizers, and the filtrate was used for the subsequent separation and extraction.

(43) (3) The clear liquid obtained in step (2) was subjected to double-stage ion exchange chromatography. The double-stage ion exchange chromatography used a cation column-anion column system, or used an anion column-cation column system, with a fixed bed model or a simulated moving bed model.

(44) The double-stage ion exchange chromatography was performed by the simulated moving bed. The filler of the simulated moving bed was cation exchange resin or anion exchange resin, such as strongly acidic cation exchange resin or strongly basic anion exchange resin. The operation temperature was 5-40° C., the feed flow rate was 2.0-10.0 BV/h, and the eluents flow rate was 1.0-8.0 BV/h. The eluents of the cation exchange resin and the anion exchange resin were a hydrochloric acid solution with a concentration of 0.30-3.0 mol/L and a NaOH solution with a concentration of 0.50-3.0 mol/L, respectively.

(45) (4) The eluate after the ion exchange chromatography in step (3) was subjected to concentration by a reverse osmosis membrane or a nanofiltration membrane. The nanofiltration membrane was a ceramic membrane, the pore size of the nanofiltration membrane was 0.5-2 nm, and the operating pressure was 2-5 atm. The reverse osmosis membrane was an organic roll type membrane or a ceramic membrane, the molecular weight cut-off was 50-100 Da, and the operating pressure was 4-10 atm.

(46) (5) the concentrated solution obtained in step (4) was subjected to vacuum drying or flash drying. The temperature of the vacuum low temperature drying was 40-80° C., and the vacuum degree was 70-95 kPa. The air temperature of the flash drying was 150-300° C. The overall recovery rate of the N-acetyl-glucosamine reached 90% or more, and the purity reached 99%.

Example 8

(47) The specific implementation mode was the same as that in Example 7. The differences were as follows: the flocculant in step (1) was a combination of two or more selections from polyacrylamide, dimethylamine-epichlorohydrin copolymer, polyferric chloride, ferric chloride, ferric sulfate and ferrous sulfate. The addition of the flocculant was 0.02-0.7% of the dry weight of the biomass, and the addition of each component was specifically as follows:

(48) The addition of the polyacrylamide was 0.005-0.15% of the dry weight of the biomass in the raw material, the addition of the dimethylamine-epichlorohydrin copolymer was 0.005-0.1% of the dry weight of the biomass, the addition of the polyferric chloride was 0.02-0.5% of the dry weight of the biomass, the addition of the ferric chloride was 0.02-0.45% of the dry weight of the biomass, the addition of the ferric sulfate was 0.02-0.5% of the dry weight of the biomass, and the addition of the ferrous sulfate was 0.04-0.4% of the dry weight of the biomass.

(49) Other steps were the same as those in Example 7. The overall recovery rate of the N-acetyl-glucosamine reached 90% or more, and the purity reached 99%.

Example 9

(50) The specific implementation mode was the same as that in Example 7. The differences were as follows: plate and frame pressure filtration was used in step (2). The filter aid was added before the pressure filtration operation, the filter aid may be one or a combination of two or more selections from diatomite, attapulgite, perlite and powdered activated carbon. The addition of the filter aid was 0.5-5% (w/v) of the raw material solution.

(51) Other steps were the same as those in Example 7. The overall recovery rate of the N-acetyl-glucosamine reached 90% or more, and the purity reached 99%.

Example 10

(52) The specific implementation mode was the same as that in Example 7. The differences were as follows: the concentrated solution obtained in step (4) was subjected to evaporation treatment and then crystallization at 5-40° C., wherein the evaporation might be the single-effect evaporation, double-effect evaporation or triple-effect evaporation.

(53) The feed liquid after the crystallization was subjected to centrifugation. The crystallized mother liquor after the centrifugation was subjected to decolorization. The crystallized mother liquor after the decolorization was conveyed into an evaporation system again for recycling, wherein a method for decolorization was activated carbon adsorption decolorization or macroporous resin decolorization.

(54) The crystal obtained after the centrifugation was dried to obtain a crystallized product of N-acetyl-glucosamine. The recovery ratio reached 90% or more, and the purity reached 99.5%.

Comparative Example 1

(55) N-acetyl-glucosamine was prepared according to a method disclosed in a patent application with an application number of CN2016112278411, and specific steps were:

(56) (1) 50 m.sup.3 of N-acetyl-glucosamine fermentation broth with a concentration of 50 kg/m.sup.3 obtained by aerobic fermentation was collected in a fermentation broth storage tank. Microbial cells were removed by filtration with a ceramic nanofiltration membrane. The pore size of the membrane was 5 nm. After the microbial cells were concentrated, 50 m.sup.3 of pure water was added to dialyze the concentrated phase of the nanofiltration membrane, and a total of 90 m.sup.3 of filtrate with an N-acetyl-glucosamine concentration of 25.3 kg/m.sup.3 was collected. Meanwhile, 10 m.sup.3 of waste residues with a high organic matter content were produced;

(57) (2) the filtrate in step (1) was pumped into an adsorption column filled with activated carbon, and the dosage of the activated carbon was 2.5 kg/m.sup.3.

(58) (3) The solution absorbed by the activated carbon in step (2) was pumped into the first column filled with strongly acidic cation resin, the resulting eluate was then pumped into the second column filled with strongly basic anion resin. The flow rate was 4.5 BV/h, and 97 m.sup.3 of eluate with an N-acetyl-glucosamine concentration of 22 kg/m.sup.3 was collected. An HCl solution with a concentration of 1.0 mol/L and an NaOH solution with a concentration of 1.0 mol/L were used to regenerate the cation resin and the anion resin. The ion exchange columns were continuously washed with deionized water to neutral pH.

(59) (4) the eluate treated in step (3) was subjected to triple-effect evaporation concentration, crystallization and drying according to the method in Example 3 to obtain 1990 kg of N-acetyl-glucosamine crystal. The overall recovery rate was 79.6%.

Comparative Example 2

(60) N-acetyl-glucosamine was prepared according to a method disclosed in a patent application with an application number of 2018103088811, and specific steps were as follows:

(61) (1) 50 m.sup.3 of N-acetyl-glucosamine fermentation broth with a concentration of 50 kg/m.sup.3 obtained by aerobic fermentation was collected in a fermentation broth storage tank. Microbial cells were removed by filtration with a ceramic ultrafiltration membrane, and the pore size of the membrane was 50 nm. After the microbial cells were concentrated, 50 m.sup.3 of pure water was added to dialyze the concentrated phase of the ultrafiltration membrane, and a total of 92 m.sup.3 of filtrate with a concentration of 25.5 kg/m.sup.3 was collected. Meanwhile, 8 m.sup.3 of waste residues with a high organic matter content were produced.

(62) (2) The filtrate of the ceramic ultrafiltration membrane in step (1) was pumped into an adsorption column filled with activated carbon, and the dosage of the activated carbon was 2 kg/m.sup.3.

(63) (3) The eluate after the adsorption and decolorization in step (2) was pumped into an electrodialysis membrane treatment system for desalination treatment. A total of 40 m.sup.3 of deionized water was added until the conductivity of the concentrated solution was lower than 50 μs/cm. The type of an electrodialysis membrane was a homogeneous ion exchange membrane. 17 m.sup.3 of a concentrated solution was obtained, and the product concentration was 126 kg/m.sup.3.

(64) (4) The concentrated solution treated in step (3) was subjected to triple-effect evaporation concentration, crystallization and drying according to the method in Example 3 to obtain 1960 kg of N-acetyl-glucosamine crystal. The overall recovery rate was 78.4%.

(65) The results of the acetyl-glucosamine extraction process using various solid-liquid separation methods were shown in Table 2.

(66) TABLE-US-00001 TABLE 1 Material consumption for extracting N-acetyl- glucosamine using various ion exchange procedures Treatment GlcNAc Usage of volume concen- acidic of the tration and Ion raw in raw Filler basic Case exchange material material loss eluents number procedure (m.sup.3) (kg/m.sup.3) (L/m.sup.3) (L/m.sup.3) Example 1 Fixed bed 46.5 50 8 200 Example 2 Simulated 50.2 49 1.5 90 moving bed Example 6 Continuous 46.5 50 6 120 moving bed

(67) TABLE-US-00002 TABLE 2 The results of acetyl-glucosamine extraction process using various solid-liquid separation methods GlcNAc Solid- Volume Consumption concentration GlcNAc liquid of solid of pure in clear recovery Case separation waste water liquid rate Description of advantages number method (m.sup.3) (m.sup.3) (kg/m.sup.3) (%) and disadvantages Example 1 Flocculation 3.5 0 50 93% A moderate amount of solid waste, less and waste water, small volume of clear continuous liquid, high concentration product, centrifuge small device occupation, and relatively low recovery rate. Example 2 Flocculation 1.8 2 49 98% Less solid waste, less wastewater, small and volume of the clear liquid, high filter press concentration product, high recovery rate, simultaneous decolorization, and low device investment. Comparative Ceramic 10 50 25.3 91% Easy sanitary control, high automation, Example 1 nanofiltration large amount of solid waste, large membrane amount of pure water, large amount of (5 nm) waste water, low product concentration, slow filtration speed, higher equipment investment, and Consumable membrane modules. Comparative Ceramic 8 50 25.5 94% Easy sanitary control, high automation, Example 2 ultrafiltration moderate equipment investment, large membrane volume of solid waste, large (50 nm) consumption of pure water, large amount of waste water, low product concentration. Note: the volume of raw material was 50 m.sup.3, and the acetyl-glucosamine concentration in the raw material solution was 50 g/L. Method for measuring chromaticity of clear liquid: 50 ml of a clear liquid was sampled and freeze-dried to obtain solid powder, the solid powder was diluted again to a concentration of 50 g/L GlcNAc, and then, chromaticity analysis was performed.

(68) Although the disclosure has been disclosed above with preferred examples, it is not intended to limit the disclosure. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the disclosure. Therefore, the protection scope of the disclosure should be defined by the claims.