METHOD FOR PREPARING NATURAL VANILLIN VIA BIOOXIDATION 4-METHYLGUAIACOL

Abstract

A method for preparing natural vanillin via biooxidation of 4-methylguaiacol comprises (1) activating a strain and preparing a seed culture; (2) fermenting; (3) bioconversion; (4) adsorbing and eluting; and (5) concentrating and crystallizing.

Claims

1. A method for preparing natural vanillin via biooxidation of 4-methylguaiacol, comprising: (1) culturing Bacillus megaterium OMK-72 on a solid slant medium and a seed medium in sequence to obtain a seed culture, wherein the Bacillus megaterium OMK-72 was deposited in the China Center for Type Culture Collection on Aug. 31, 2020, with a deposition number of CCTCC NO: M 2020457; (2) inoculating the seed culture into a fermentation medium and cultivating until the Bacillus megaterium OMK-72 grows to an early logarithmic stage, then adding 1.8-2.2 g/L of 4-methylguaiacol to induce an expression of correlated enzymes, and cultivating until fermentation is complete to obtain a culture; (3) adding 4-methylguaiacol into the culture obtained in step (2) at one time or several times, and stirring under aeration conditions to obtain a bioconversion mixture, wherein during this step, a concentration of the 4-methylguaiacol for each addition is 4.5-5.5 g/L; (4) centrifuging the bioconversion mixture obtained in step (3) to obtain a supernatant, letting the supernatant to pass through a ceramic membrane to obtain a clear solution, letting the clear solution to pass through a resin column for absorption, and then eluting the resin column with ethanol to obtain an eluate; and (5) evaporating and concentrating the eluate, then crystallizing, and drying to obtain the natural vanillin.

2. The method according to claim 1, wherein: (a) culturing the Bacillus megaterium OMK-72 on the solid slant medium and the seed medium in sequence comprises streaking the Bacillus megaterium OMK-72 from a cryopreserved glycerol tube on the solid slant medium and then culturing at 28-30° C. for 24-48 hours to obtain an activated strain, and inoculating the activated strain into the seed medium and culturing to the early logarithmic stage at 28-30° C. and 200-250 rpm with shaking to obtain the seed culture; (b) inoculating the seed culture into the fermentation medium and cultivating until the Bacillus megaterium OMK-72 grows to the early logarithmic stage, then adding 1.8-2.2 g/L of the 4-methylguaiacol to induce the expression of the correlated enzymes, and cultivating until the fermentation is complete to obtain the culture comprises inoculating the seed culture obtained in step (a) into the fermentation medium with a volume ratio of 5-10% and cultivating for 3-6 hours under conditions of pH 6.5-8.0, 28-30° C., a stirring speed of 100-600 rpm, and an aeration rate of 1:0.5, when the Bacillus megaterium OMK-72 grows to the early logarithmic stage, adding 1.8-2.2 g/L of the 4-methylguaiacol and continuing to ferment for another 36-48 hours to obtain the culture; (c) stirring under the aeration conditions comprises bioconversing under conditions of a stirring speed of 300-600 rpm and an aeration rate of 1:0.5; and (d) evaporating and concentrating the eluate, then crystallizing, and then drying to obtain the natural vanillin comprises transferring the eluate obtained in step (4) to a distillation flask, evaporating an amount of the ethanol, concentrating, crystallizing under a condition, and drying to obtain the natural vanillin.

3. The method according to claim 1, wherein a composition of the solid slant medium has the following mass percentages: peptone 1-2%, yeast extract 0.5-1%, sodium chloride 0.5-1%, agar 1.5-2%, and the rest is water.

4. The method according to claim 1, wherein a composition of the solid slant medium has the following mass percentages: peptone 1%, yeast extract 0.5%, sodium chloride 1%, agar 2%, and the rest is water.

5. The method according to claim 1, wherein a composition of the seed medium has the following mass percentages: peptone 1-2%, yeast extract 0.5-1%, sodium chloride 0.5-1%, and the rest is water.

6. The method according to claim 1, wherein a composition of the seed medium has the following mass percentages: peptone 1%, yeast extract 0.5%, sodium chloride 1%, and the rest is water.

7. The method according to claim 1, wherein: a composition of the fermentation medium has the following mass percentages: glucose 2.0-5.0%, ammonium dihydrogen phosphate 0.5-1.0%, potassium dihydrogen phosphate 0.1-0.5%, magnesium sulfate 0.05-0.2%, calcium sulfate 0.05-0.1%, yeast extract powder 0.1-1.0%, trace element solution 0.1-0.2%, and a solvent of the fermentation medium is water; and a composition of the trace element solution has the following mass percentages: ethylenediaminetetraacetic acid (EDTA) 0.8 -1.2%, zinc sulfate 0.1-0.3%, calcium chloride 0.08-0.12%, ferrous sulfate 0.45-0.55%, sodium molybdate 0.01-0.03%, copper sulfate 0.01-0.03%, cobalt chloride 0.03-0.05%, manganese chloride is 0.08-0.12%, and a solvent of the trace element solution is water.

8. The method according to claim 1, wherein: a composition of the fermentation medium has the following mass percentages: glucose 2%, ammonium dihydrogen phosphate 1%, potassium dihydrogen phosphate 0.5%, magnesium sulfate 0.2%, calcium sulfate 0.1%, yeast extract powder 0.5%, trace element solution 0.1%, and the rest is water; and the trace element solution has the following mass percentages: ethylenediaminetetraacetic acid (EDTA) 1%, zinc sulfate 0.2%, calcium chloride 0.1%, ferrous sulfate 0.5%, sodium molybdate 0.02%, copper sulfate 0.02%, cobalt chloride 0.04%, manganese chloride 0.1%, and a solvent of the trace element solution is water.

9. Bacillus megaterium OMK-72 deposited in the China Center for Type Culture Collection on Aug. 31, 2020, with a deposit number of CCTCC NO: M 2020457.

10. A method for preparing natural vanillin via biooxidation of 4-methylguaiacol using the Bacillus megaterium OMK-72 according to claim 9.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 illustrates the high performance liquid chromatography (HPLC) graph of vanillin of Embodiment 2 of the present disclosure, produced by fermentation and oxidation of 4-methylguaiacol using Bacillus megaterium OMK-72.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The present disclosure will be further described in combination with the accompanying embodiments and drawings.

Embodiment 1: Preparation of Natural Vanillin (Fermentation Using Shaking Flask)

[0032] (1) Acquisition of a strain

[0033] The strain used to biooxidize 4-methylguaiacol to produce vanillin is isolated from marine sediments. The strain is identified as Bacillus megaterium by 16S ribosomal deoxyribonucleic acid (rDNA) sequencing and named as Bacillus megaterium OMK-72. The strain was deposited in the China Center for Type Culture Collection (located in Wuhan University, Wuhan, China) on Aug. 31, 2020, with the deposit number: CCTCC NO: M 2020457.

[0034] (2) Activation of the strain: Bacillus megaterium OMK-72 from a glycerol tube at −80° C. is streaked on a solid slant medium and is cultured at 30° C. for 24 hours.

[0035] The component of the solid slant medium has the following mass percentages: peptone 1%, yeast extract 0.5%, sodium chloride 1%, agar 2%, and the rest is water.

[0036] (3) Preparation of a seed culture (i.e., a seed culture solution): the activated strain is inoculated into a 500 mL shaking flask containing 30 mL of a seed medium and is cultivated at 30° C. and 250 revolutions per minute (rpm) for 4-6 hours to obtain the seed culture.

[0037] The component of the seed medium has the following mass percentages: peptone 1%, yeast extract 0.5%, sodium chloride 1%, and the rest is water. The initial pH is 7.5, and the seed medium is sterilized at 121° C. for 20 minutes.

[0038] (4) Fermentation and bioconversion: 5 mL of the seed culture is inoculated into a 500 mL shaking flask containing 50 mL of a fermentation medium and is fermented at 30° C. and 250 rpm for 4 hours. After the strain grows to a logarithmic growth phase, 2 g/L of 4-methylguaiacol is added, and the strain is let to continue fermenting at 30° C. and 250 rpm for 36 hours. After the fermentation is complete, 5 g/L of 4-methylguaiacol is added to be converted for 10 hours to achieve complete conversion to obtain a fermentation broth. The concentration of the vanillin in the fermentation broth is 5.4 g/L and a yield of 98% is achieved as measured by a HPLC analysis.

[0039] The composition of the fermentation medium has the following mass percentages: glucose 2%, ammonium dihydrogen phosphate 1%, potassium dihydrogen phosphate 0.5%, magnesium sulfate 0.2%, calcium sulfate 0.1%, yeast extract powder 0.5%, trace element solution 0.1%, and the rest is water. The initial pH is 7.5, and the fermentation medium is sterilized at 115° C. for 30 minutes, wherein the trace element solution has the following mass percentages: ethylenediaminetetraacetic acid (EDTA) 1%, zinc sulfate 0.2%, calcium chloride 0.1%, ferrous sulfate 0.5%, sodium molybdate 0.02%, copper sulfate 0.02%, cobalt chloride 0.04%, manganese chloride 0.1%, and the solvent is water.

Embodiment 2: Preparation of Natural Vanillin (i.e., Vanillin) (Fermentation Using a Fermentation Tank)

[0040] Steps (1) to (2) are the same as Embodiment 1.

[0041] (3) Preparation of a seed culture (i.e., a seed culture solution): the activated strain is inoculated into a 500 mL shaking flask containing 50 mL of a seed medium and is cultivated at 30° C. and 250 rpm for 6-8 hours to obtain a first stage seed culture (i.e., a first stage seed solution); 50 mL of the first stage seed culture is inoculated into a 10 L seed tank containing 6 L of the seed medium and is cultivated at 30° C. for 6-8 hours with a stirring speed of 250 rpm and an aeration rate of 1:0.5 to obtain a second stage seed culture (i.e., a second stage seed solution).

[0042] The composition of the seed medium is the same as Embodiment 1.

[0043] (4) Fermentation and bioconversion: 15 L of a fermentation medium is added into a 30 L fermenter and is sterilized at 115° C. for 30 minutes, and the second stage seed culture is inoculated into the 30 L fermenter to be cultivated with 10% inoculum volume. The cultivation condition is as follows: the temperature is 30° C., the stirring speed is 400 rpm, the aeration ratio is 1:0.5. After the fermentation lasts for 5 hours, 2 g/L of 4-methylguaiacol is added, and 70% of a glucose solution is added at a flow rate of 20 g/h. The total fermentation duration is 48 hours. After the fermentation is complete, 5 g/L of the 4-methylguaiacol is added to be converted into the vanillin with a stirring speed of 400 rpm and an aeration ratio of 1:0.5, and two extra portions of 5 g/L of 4-methylguaiacol is then respectively supplemented at 6 hours and 15 hours after the first portion of 4-methylguaiacol is added. The total bioconversion time is 26 hours, the conversion rate for 4-methylguaiacol reaches 100%, the vanillin concentration of the bioconversion mixture is 16.2 g/L, and the yield is 98%. (The HPLC graph is shown in FIG. 1, and a characteristic peak of the natural vanillin is referenced by the arrow).

[0044] The composition of the fermentation medium is the same as Embodiment 1.

[0045] (5) Adsorption and elution by a resin column: after the bioconversion is complete, the temperature is increased to 60° C. for inactivation of the strain, then the bioconversion mixture obtained in step (4) is centrifuged to obtain the supernatant. The supernatant is let to pass through by a ceramic membrane to remove the insolubles to obtain a clear solution. The clear solution is let to pass through a resin column for absorption and is then eluted with ethanol to obtain an ethanol solution containing the vanillin (e.g., one of eluates).

[0046] (6) Concentration and crystallization: the ethanol solution containing the vanillin obtained in step (5) is transferred into a distillation flask to remove an appropriate amount of ethanol to be concentrated, then crystallized under appropriate conditions, and dried to obtain 253 g of the pure natural vanillin. The isolated yield is 88%.

[0047] The aforementioned embodiments are merely some embodiments of the present disclosure, and the scope of the disclosure is not limited thereto. Thus, it is intended that the present disclosure cover any modifications and variations of the presently presented embodiments provided they are made without departing from the appended claims and the specification of the present disclosure.