Method for reducing acetic acid in succinic acid fermentation process

Abstract

The invention provides a method for reducing acetic acid in a succinic acid fermentation process, and belongs to the technical field of fermentation. In the step of fermentation culture, a fermentation aid is fed in a fermentation culture process, specifically, when fermentation is performed for 10h, a fermentation aid I is fed into a fermentation culture tank at the feeding speed of 0.07-0.09 ml / h / L until fermentation is finished; when the fermentation is performed for 24 hours, feeding a fermentation aid II into the fermentation culture tank at the feeding speed of 0.12-0.14 ml / h / L until the fermentation is finished; the fermentation aid I comprises cobalt chloride hexahydrate, zinc sulfate heptahydrate, folic acid and biotin; the fermentation auxiliary agent II comprises nicotinamide, cysteine and tyrosine; the content of the fermentation culture solution prepared by the method disclosed by the invention is as high as 59.1-60.4 g / L, the content of acetic acid is as low as 0.30-0.65 g / L, and the content of malic acid is 0.20-0.23 g / L.

Description

Technical Field

[0001] The invention belongs to the technical field of fermentation, and in particular relates to a method for reducing acetic acid in a succinic acid fermentation process. Background Art

[0002] Succinic acid is a dibasic organic carboxylic acid containing four carbon atoms and is an important chemical raw material. Succinic acid can produce a sour taste and can be used in seasonings, soy sauce and other fields. It can be used as a preservative, pH adjuster, and co-solvent. It can also be used to synthesize antidotes, diuretics, sedatives, etc. It has a wide range of applications.

[0003] Succinic acid can be produced by chemical synthesis, but it causes serious environmental pollution and has high production costs. With the development of society, fermentation has become a new method for preparing succinic acid. The fermentation method uses microorganisms such as bacteria and yeast, and uses sugar as raw materials to produce succinic acid under normal temperature and pressure. The fermentation method avoids dependence on petrochemical raw materials and reduces the pollution of the chemical synthesis process to the environment. It has the advantages of environmental protection, simple equipment, and low cost. Therefore, fermentation is currently the main method for producing succinic acid. Escherichia coli is widely used because of its clear genetic characteristics, easy cultivation, and ability to achieve efficient expression of target genes. However, Escherichia coli produces acetic acid when it grows. The production and accumulation of acetic acid not only affects the growth of the bacteria, but also inhibits the synthesis of the product.

[0004] CN117004658A discloses a production process for producing succinic acid by fermentation, specifically using Escherichia coli as a production strain, firstly performing microaerobic fermentation, then performing anaerobic fermentation, during the anaerobic fermentation process, introducing carbon dioxide as a supplementary carbon source, and finally obtaining succinic acid; This patent increases the yield of succinic acid, but the acetic acid content is high and the yield of succinic acid is still at a low level. Summary of the invention

[0005] In order to solve the technical problems existing in the prior art, the present invention provides a method for reducing acetic acid in the process of succinic acid fermentation, which can effectively reduce the content of acetic acid in the process of succinic acid fermentation and has a high yield of succinic acid.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: A method for reducing acetic acid in a succinic acid fermentation process, comprising shake flask culture, seed culture and fermentation culture, as follows: 1. Shake flask culture The yeast on the plate is inoculated into a shake flask medium for cultivation at a temperature of 35-37° C. for 14-16 hours and a shaking frequency of 174-185 rpm. After the cultivation is completed, a shake flask culture solution is obtained; The shaking flask culture medium consists of the following components: 5.7-6.2 g / L tryptone, 4.3-4.7 g / L NaCl, 4.7-5.3 g / L yeast powder, and a pH value of 7.0.

[0007] 2. Seed Culture The shake flask culture solution is inoculated into the seed culture medium at an inoculation rate of 0.8-1.0% by volume for seed culture, the culture time is 13-15 hours, the temperature is 35-37° C., the rotation speed is 305-314 rpm, the pressure is 0.05-0.07 MPa, the air volume is 7-9 L / min, and the pH value is controlled to 6.5-6.7 by ammonia water during the culture process to obtain the seed culture solution; The seed culture medium is composed of the following ingredients: 26-30 g / L glucose, 14-16 g / L potassium dihydrogen phosphate, 11-13 g / L yeast powder, 3.5-4.5 g / L ammonium sulfate, 1.4-2.0 g / L magnesium sulfate heptahydrate, 1.3-1.5 g / L citric acid, 2.2-2.6 ml / L auxiliary mixed solution, 1.2-1.4 mg / L vitamin B1, 0.022-0.026 mg / L riboflavin, and 0.04-0.06 mg / L biotin; The components of the auxiliary mixed solution are: 1.4-1.6 g / L of boric acid, 2.4-2.8 g / L of sodium molybdate, 3.1-3.3 g / L of nickel sulfate hexahydrate, and 4-6 g / L of manganese sulfate monohydrate.

[0008] 3. Fermentation culture The seed culture solution is inoculated into a fermentation medium at an inoculation rate of 4-6% for fermentation culture, and aerobic fermentation is first performed, the fermentation temperature is controlled at 35-37°C, the ventilation volume is 1.6-1.9vvm, the rotation speed is 460-480rpm, the dissolved oxygen content is 13-17%, the pH value is controlled at 6.5-6.7, a glucose solution with a mass concentration of 53-55% is added so that the glucose content is controlled at 9-12g / L, and after 13-15h of fermentation culture, it is converted to anaerobic fermentation, carbon dioxide is introduced, the ventilation volume is controlled at 0.8-1.2vvm, and the fermentation cycle is 36.3-37.9h to obtain a fermentation culture solution; The fermentation medium is composed of the following ingredients: 19-21 g / L glucose, 3-5 g / L yeast powder, 10-12 g / L potassium dihydrogen phosphate, 3.0-3.2 g / L citric acid, 2.6-3.0 g / L ammonium sulfate, 1.0-1.4 g / L magnesium sulfate heptahydrate, 58-63 mg / L ferrous sulfate heptahydrate, and 0.7-0.9 mg / L vitamin B1; The fermentation culture includes adding a fermentation aid during the fermentation culture, specifically: At the 10th hour of fermentation, a fermentation aid 1 was added to the fermentation culture tank at a flow rate of 0.07-0.09 ml / h / L until the fermentation was completed; At the 24th hour of fermentation, the fermentation aid 2 was added into the fermentation culture tank at a flow rate of 0.12-0.14 ml / h / L until the fermentation was completed; The fermentation aid 1 comprises 0.3-0.5 g / L of cobalt chloride hexahydrate, 6-8 g / L of zinc sulfate heptahydrate, 1.6-1.8 mg / L of folic acid, and 0.03-0.06 g / L of biotin; The fermentation aid 2 comprises nicotinamide 5-7 g / L, cysteine ​​2.0-2.2 g / L, and tyrosine 1.8-2.3 g / L.

[0009] The yeast is Pichia pastoris, which is classified and named Pichia sp. , deposited in Guangdong Provincial Microbiological Culture Collection Center, the deposit address is 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou, the deposit number is GDMCC No: 64917, and the deposit date is July 26, 2024.

[0010] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. The present invention uses a method of adding glucose in a stream to maintain a low glucose intake rate in the middle and late stages of fermentation, which is beneficial to inhibiting the formation of by-products such as acetic acid and malic acid, maintaining the proliferation efficiency of the strain, and avoiding the defects of "using high-concentration initial sugar fermentation, the early growth of the bacteria is inhibited, resulting in a large amount of acetic acid accumulation and a low yield of succinic acid; using low-concentration initial sugar fermentation is not conducive to the proliferation of the strain, thereby affecting the synthesis of the product and resulting in an extension of the fermentation cycle"; The present invention adds a fermentation aid 1 in the early stage of fermentation culture, wherein cobalt chloride hexahydrate and zinc sulfate heptahydrate can be used as enzyme activators, and biotin as a growth factor can promote the growth of bacteria and the synthesis of succinic acid, and combines with folic acid to promote cell division growth and amino acid synthesis, thereby reducing the generation of by-products and increasing the yield of succinic acid; and adds a fermentation aid 2 in the middle and late stages of fermentation, wherein nicotinamide can provide nitrogen elements for bacterial growth and fermentation acid production, promotes the metabolism of microorganisms, maintains the growth vitality of strains, and improves acid production performance, and combines with cysteine ​​and tyrosine to increase the yield of succinic acid while reducing the accumulation of acetic acid and malic acid; 2. The fermentation culture broth prepared by the method of the present invention has a succinic acid content as high as 59.1-60.4 g / L, an acetic acid content as low as 0.30-0.65 g / L, and a malic acid content of 0.20-0.23 g / L. DETAILED DESCRIPTION

[0011] In order to more clearly understand the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described.

[0012] The yeast involved in the embodiment is Pichia pastoris ( Pichia sp. ), the deposit number is GDMCC No:64917, it was collected and isolated and purified in Nanning, Guangxi, China in April 2024.

[0013] Example 1 1. Shake flask culture The yeast on the plate was inoculated into a shake flask medium for cultivation at a temperature of 36°C for 15 hours and a shaking frequency of 180 rpm. After the cultivation was completed, a shake flask culture solution was obtained. The shaking flask culture medium consists of the following ingredients: 6 g / L tryptone, 4.5 g / L NaCl, 5 g / L yeast powder, and a pH value of 7.0.

[0014] 2. Seed Culture The shake flask culture solution was inoculated into the seed culture medium at an inoculum rate of 0.9% by volume for seed culture. The culture time was 14 hours, the temperature was 36° C., the rotation speed was 310 rpm, the pressure was 0.06 MPa, the air volume was 8 L / min, and the pH value was controlled to 6.6 by ammonia water during the culture process to obtain the seed culture solution. The seed culture medium is composed of the following ingredients: 28 g / L glucose, 15 / L potassium dihydrogen phosphate, 12 g / L yeast powder, 4 g / L ammonium sulfate, 1.7 g / L magnesium sulfate heptahydrate, 1.4 g / L citric acid, 2.4 ml / L auxiliary mixed solution, 1.3 mg / L vitamin B1, 0.024 mg / L riboflavin, and 0.05 mg / L biotin; The components of the auxiliary mixed solution are: 1.5 g / L boric acid, 2.6 g / L sodium molybdate, 3.2 g / L nickel sulfate hexahydrate, and 5 g / L manganese sulfate monohydrate.

[0015] 3. Fermentation culture The seed culture solution was inoculated into the fermentation medium at an inoculation rate of 5% for fermentation culture. First, aerobic fermentation was carried out, the fermentation temperature was controlled at 36°C, the ventilation volume was 1.7vvm, the rotation speed was 470rpm, the dissolved oxygen content was 15%, the pH value was controlled at 6.6, a glucose solution with a mass concentration of 54% was added so that the glucose content was controlled at 11g / L, and after 14h of fermentation culture, it was converted to anaerobic fermentation, carbon dioxide was introduced, the ventilation volume was controlled at 1.0vvm, and the fermentation cycle was 36.3h to obtain a fermentation culture solution; The fermentation medium is composed of the following ingredients: 20 g / L glucose, 4 g / L yeast powder, 11 g / L potassium dihydrogen phosphate, 3.1 g / L citric acid, 2.8 g / L ammonium sulfate, 1.2 g / L magnesium sulfate heptahydrate, 61 mg / L ferrous sulfate heptahydrate, and 0.8 mg / L vitamin B1; The fermentation culture includes adding a fermentation aid during the fermentation culture, specifically: At the 10th hour of fermentation, a fermentation aid 1 was added to the fermentation culture tank at a flow rate of 0.08 ml / h / L until the fermentation was completed; At the 24th hour of fermentation, the fermentation aid 2 was added into the fermentation culture tank at a flow rate of 0.13 ml / h / L until the fermentation was completed; The fermentation aid 1 comprises 0.4 g / L cobalt chloride hexahydrate, 7 g / L zinc sulfate heptahydrate, 1.7 mg / L folic acid, and 0.04 g / L biotin; The fermentation aid 2 comprises 6 g / L nicotinamide, 2.1 g / L cysteine ​​and 2 g / L tyrosine.

[0016] The fermentation broth prepared by the method of Example 1 above had a succinic acid content of 60.4 g / L, an acetic acid content of 0.41 g / L, and a malic acid content of 0.20 g / L.

[0017] Example 2 1. Shake flask culture The yeast on the plate was inoculated into a shake flask medium for cultivation at a temperature of 35°C for 14 hours and a shaking frequency of 174 rpm. After the cultivation was completed, a shake flask culture solution was obtained. The shaking flask culture medium consists of the following components: 5.7 g / L tryptone, 4.3 g / L NaCl, 4.7 g / L yeast powder, and a pH value of 7.0.

[0018] 2. Seed Culture The shake flask culture solution was inoculated into the seed culture medium at an inoculum rate of 0.8% by volume for seed culture. The culture time was 13 hours, the temperature was 35° C., the rotation speed was 305 rpm, the pressure was 0.05 MPa, the air volume was 7 L / min, and the pH value was controlled to 6.5 by ammonia water during the culture process to obtain the seed culture solution. The seed culture medium is composed of the following ingredients: 26 g / L glucose, 14 / L potassium dihydrogen phosphate, 11 g / L yeast powder, 3.5 g / L ammonium sulfate, 1.4 g / L magnesium sulfate heptahydrate, 1.3 g / L citric acid, 2.2 ml / L auxiliary mixed solution, 1.2 mg / L vitamin B1, 0.022 mg / L riboflavin, and 0.04 mg / L biotin; The components of the auxiliary mixed solution are: 1.4 g / L boric acid, 2.4 g / L sodium molybdate, 3.1 g / L nickel sulfate hexahydrate, and 4 g / L manganese sulfate monohydrate.

[0019] 3. Fermentation culture The seed culture solution was inoculated into the fermentation medium at an inoculation rate of 4% for fermentation culture. First, aerobic fermentation was carried out, the fermentation temperature was controlled at 35°C, the ventilation volume was 1.6vvm, the rotation speed was 460rpm, the dissolved oxygen content was 13%, the pH value was controlled at 6.5, and a glucose solution with a mass concentration of 53% was added so that the glucose content was controlled at 9g / L. After 13h of fermentation culture, the fermentation was switched to anaerobic fermentation, carbon dioxide was introduced, the ventilation volume was controlled at 0.8vvm, and the fermentation period was 37.9h to obtain a fermentation culture solution. The fermentation medium is composed of the following ingredients: 19 g / L glucose, 3 g / L yeast powder, 12 g / L potassium dihydrogen phosphate, 3.0 g / L citric acid, 2.6 g / L ammonium sulfate, 1.4 g / L magnesium sulfate heptahydrate, 58 mg / L ferrous sulfate heptahydrate, and 0.9 mg / L vitamin B1; The fermentation culture includes adding a fermentation aid during the fermentation culture, specifically: At the 10th hour of fermentation, a fermentation aid 1 was added to the fermentation culture tank at a flow rate of 0.07 ml / h / L until the fermentation was completed; At the 24th hour of fermentation, the fermentation aid 2 was added into the fermentation culture tank at a flow rate of 0.12 ml / h / L until the fermentation was completed; The fermentation aid 1 comprises 0.3 g / L of cobalt chloride hexahydrate, 8 g / L of zinc sulfate heptahydrate, 1.6 mg / L of folic acid, and 0.06 g / L of biotin; The ingredients of the fermentation aid 2 are nicotinamide 5 g / L, cysteine ​​2.0 g / L, and tyrosine 2.3 g / L.

[0020] The fermentation broth prepared by the method of Example 2 above had a succinic acid content of 59.1 g / L, an acetic acid content of 0.65 g / L, and a malic acid content of 0.23 g / L.

[0021] Example 3 1. Shake flask culture The yeast on the plate was inoculated into a shake flask medium for cultivation at a temperature of 37°C for 16 hours and a shaking frequency of 185 rpm. After the cultivation was completed, a shake flask culture solution was obtained. The shaking flask culture medium consists of the following components: 6.2 g / L tryptone, 4.7 g / L NaCl, 5.3 g / L yeast powder, and a pH value of 7.0.

[0022] 2. Seed Culture The shake flask culture solution was inoculated into the seed culture medium at an inoculation rate of 1.0% by volume for seed culture. The culture time was 15 hours, the temperature was 37° C., the rotation speed was 314 rpm, the pressure was 0.07 MPa, the air volume was 9 L / min, and the pH value was controlled at 6.7 by ammonia water during the culture process to obtain the seed culture solution. The seed culture medium is composed of the following ingredients: 30 g / L glucose, 16 g / L potassium dihydrogen phosphate, 13 g / L yeast powder, 4.5 g / L ammonium sulfate, 2.0 g / L magnesium sulfate heptahydrate, 1.5 g / L citric acid, 2.6 ml / L auxiliary mixed solution, 1.4 mg / L vitamin B1, 0.026 mg / L riboflavin, and 0.06 mg / L biotin; The components of the auxiliary mixed solution are: 1.6 g / L boric acid, 2.8 g / L sodium molybdate, 3.3 g / L nickel sulfate hexahydrate, and 6 g / L manganese sulfate monohydrate.

[0023] 3. Fermentation culture The seed culture solution was inoculated into the fermentation medium at an inoculation rate of 6% for fermentation culture. First, aerobic fermentation was carried out, the fermentation temperature was controlled at 37°C, the ventilation volume was 1.9vvm, the rotation speed was 480rpm, the dissolved oxygen content was 17%, the pH value was controlled at 6.7, a glucose solution with a mass concentration of 55% was added so that the glucose content was controlled at 12g / L, and after 15h of fermentation culture, it was converted to anaerobic fermentation, carbon dioxide was introduced, the ventilation volume was controlled at 1.2vvm, and the fermentation cycle was 36.8h to obtain a fermentation culture solution; The fermentation medium is composed of the following ingredients: 21 g / L glucose, 5 g / L yeast powder, 10 g / L potassium dihydrogen phosphate, 3.2 g / L citric acid, 3.0 g / L ammonium sulfate, 1.0 g / L magnesium sulfate heptahydrate, 63 mg / L ferrous sulfate heptahydrate, and 0.7 mg / L vitamin B1; The fermentation culture includes adding a fermentation aid during the fermentation culture, specifically: At the 10th hour of fermentation, a fermentation aid 1 was added to the fermentation culture tank at a flow rate of 0.09 ml / h / L until the fermentation was completed; At the 24th hour of fermentation, the fermentation aid 2 was added into the fermentation culture tank at a flow rate of 0.14 ml / h / L until the fermentation was completed; The fermentation aid 1 comprises 0.5 g / L of cobalt chloride hexahydrate, 6 g / L of zinc sulfate heptahydrate, 1.8 mg / L of folic acid, and 0.03 g / L of biotin; The ingredients of the fermentation aid 2 are 7 g / L nicotinamide, 2.2 g / L cysteine, and 1.8 g / L tyrosine.

[0024] The fermentation broth prepared by the method of Example 3 above had a succinic acid content of 59.8 g / L, an acetic acid content of 0.30 g / L, and a malic acid content of 0.22 g / L.

[0025] Comparative Example 1 Based on Example 1, the change is that the components of fermentation aid 1 and fermentation aid 2 are directly added to the fermentation medium; The fermentation medium is composed of the following ingredients: 20 g / L glucose, 4 g / L yeast powder, 11 g / L potassium dihydrogen phosphate, 3.1 g / L citric acid, 2.8 g / L ammonium sulfate, 1.2 g / L magnesium sulfate heptahydrate, 61 mg / L ferrous sulfate heptahydrate, 0.8 mg / L vitamin B1, 2.1 ml / L fermentation aid 1, and 1.5 ml / L fermentation aid 2; The fermentation aid 1 comprises 0.4 g / L cobalt chloride hexahydrate, 7 g / L zinc sulfate heptahydrate, 1.7 mg / L folic acid, and 0.04 g / L biotin; The fermentation aid 2 comprises 6 g / L nicotinamide, 2.1 g / L cysteine ​​and 2 g / L tyrosine; The rest of the operations are the same; The fermentation culture broth prepared by the method of Comparative Example 1 had a succinic acid content of 47.5 g / L, an acetic acid content of 2.78 g / L, and a malic acid content of 1.22 g / L.

[0026] In Comparative Example 1, the components of fermentation aids 1 and 2 are added to the fermentation medium. In the early stage of fermentation, the bacterial body grows faster and the bacterial body biomass is higher. The high specific growth rate will lead to an increase in acetic acid. Directly adding growth factors and other components to the fermentation medium will greatly increase the accumulation of acetic acid; and zinc, cobalt, tyrosine and cysteine ​​are added to the fermentation medium. The secretion of the enzyme is small in the early stage of fermentation, which cannot effectively promote the fermentation reaction, thereby increasing the by-products and the yield of succinic acid is low; and after a period of fermentation, the feeding method is adopted. When the bacterial body enters the main fermentation period, the growth is weak, the vitality decreases, and the acid production level decreases. Nicotinamide can be added with nitrogen source in time, and it combines with the growth factors cobalt, zinc, tyrosine and cysteine ​​to promote the growth of the bacterial body and the activity of the enzyme. Under the mutual influence and joint action, while increasing the yield of succinic acid, the accumulation of by-products such as acetic acid and malic acid is reduced, and the conversion rate is improved.

[0027] Comparative Example 2 Based on Example 1, the change is that the step of adding the fermentation aid is omitted, and the other operations are the same.

[0028] The fermentation culture broth prepared by the method of Comparative Example 2 had a succinic acid content of 42.1 g / L, an acetic acid content of 6.84 g / L, and a malic acid content of 1.64 g / L.

[0029] Comparative Example 2 omitted the fermentation aid component. When the bacteria grew weakly and their vitality decreased during the main fermentation period, they could not effectively supplement nutrients in the middle and late stages of fermentation. During the synthesis of aromatic amino acids during the fermentation process, they failed to add zinc, cobalt, tyrosine, cysteine ​​and other components in time, thereby affecting the production and synthesis rate of succinic acid, resulting in incomplete fermentation, increased by-products and low conversion rate.

[0030] The present invention uses a method of adding glucose in a stream, and in the middle and late stages of fermentation, maintains a low glucose intake rate, which is beneficial to inhibiting the formation of by-products such as acetic acid and malic acid, maintaining the proliferation efficiency of the strain, and avoiding the defects of "using high-concentration initial sugar fermentation, the early growth of the bacterial body is inhibited, resulting in a large amount of acetic acid accumulation and a low yield of succinic acid; using low-concentration initial sugar fermentation is not conducive to the proliferation of the strain, thereby affecting the synthesis of the product and prolonging the fermentation cycle". In the present invention, the first fermentation aid is added in the early stage of fermentation culture, wherein cobalt chloride hexahydrate and zinc sulfate heptahydrate can be used as enzyme activators, and biotin is used as a growth factor to promote the growth of the bacterial body and the synthesis of succinic acid, and the biotin is combined with folic acid to promote the division and growth of cells and the synthesis of amino acids, thereby reducing the generation of by-products and increasing the yield of succinic acid. The second fermentation aid is added in the middle and late stages of fermentation, wherein nicotinamide can provide nitrogen elements for bacterial growth and fermentation acid production, promotes the metabolism of microorganisms, maintains the growth vitality of the strain, and improves the acid production performance. The nicotinamide is combined with cysteine ​​and tyrosine to increase the yield of succinic acid while reducing the accumulation of acetic acid and malic acid.

[0031] Unless otherwise specified, all percentages used in the present invention are by mass.

[0032] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for reducing acetic acid in a succinic acid fermentation process, characterized in that: The method includes shake flask culture, seed culture and fermentation culture; The shake flask culture step comprises: taking yeast and inoculating it into a shake flask medium for culture; The yeast is Pichia pastoris ( Pichia sp. ), the deposit number is GDMCC No:64917; The fermentation culture step comprises the following steps: inoculating the seed culture solution into the fermentation medium, firstly performing aerobic fermentation, controlling the dissolved oxygen content to 13-17%, adding glucose solution so that the glucose content is controlled to 9-12 g / L, and after 13-15 hours of fermentation culture, switching to anaerobic fermentation, introducing carbon dioxide, controlling the ventilation volume to 0.8-1.2 vvm, and the fermentation cycle to 36.3-37.9 hours, to obtain the fermentation culture solution; In the fermentation and culturing step, a fermentation aid is added during the fermentation and culturing process, specifically: At the 10th hour of fermentation, a fermentation aid 1 was added to the fermentation culture tank at a flow rate of 0.07-0.09 ml / h / L until the fermentation was completed; At the 24th hour of fermentation, the fermentation aid 2 was added into the fermentation culture tank at a flow rate of 0.12-0.14 ml / h / L until the fermentation was completed; The fermentation aid 1 is composed of cobalt chloride hexahydrate, zinc sulfate heptahydrate, folic acid and biotin; The second fermentation aid is composed of nicotinamide, cysteine ​​and tyrosine.

2. The method for reducing acetic acid in a succinic acid fermentation process according to claim 1, characterized in that: The fermentation medium is composed of the following ingredients: 19-21 g / L glucose, 3-5 g / L yeast powder, 10-12 g / L potassium dihydrogen phosphate, 3.0-3.2 g / L citric acid, 2.6-3.0 g / L ammonium sulfate, 1.0-1.4 g / L magnesium sulfate heptahydrate, 58-63 mg / L ferrous sulfate heptahydrate, and 0.7-0.9 mg / L vitamin B1.

3. The method for reducing acetic acid in a succinic acid fermentation process according to claim 1, characterized in that: The fermentation and culturing step comprises: inoculating the seed culture solution into the fermentation medium at an inoculation rate of 4-6% for fermentation and culturing; firstly, performing aerobic fermentation, controlling the fermentation temperature to 35-37°C, the ventilation volume to 1.6-1.9 vvm, the rotation speed to 460-480 rpm, the dissolved oxygen content to 13-17%, controlling the pH value to 6.5-6.7, adding a glucose solution with a mass concentration of 53-55% so that the glucose content is controlled to 9-12 g / L, and after 13-15 hours of fermentation and culturing, switching to anaerobic fermentation, introducing carbon dioxide, controlling the ventilation volume to 0.8-1.2 vvm, and the fermentation cycle to 36.3-37.9 hours, to obtain a fermentation culture solution; The fermentation aid 1 comprises 0.3-0.5 g / L of cobalt chloride hexahydrate, 6-8 g / L of zinc sulfate heptahydrate, 1.6-1.8 mg / L of folic acid, and 0.03-0.06 g / L of biotin; The fermentation aid 2 comprises nicotinamide 5-7 g / L, cysteine ​​2.0-2.2 g / L, and tyrosine 1.8-2.3 g / L.

4. The method for reducing acetic acid in a succinic acid fermentation process according to claim 1, characterized in that: The shaking flask culture step comprises taking the yeast on the plate and inoculating it into the shaking flask medium for culture at a temperature of 35-37° C., a culture time of 14-16 hours, and a shaking frequency of 174-185 rpm, and obtaining the shaking flask culture fluid after the culture is completed.

5. The method for reducing acetic acid in a succinic acid fermentation process according to claim 4, characterized in that: The shaking flask culture medium consists of the following components: 5.7-6.2 g / L tryptone, 4.3-4.7 g / L NaCl, 4.7-5.3 g / L yeast powder, and a pH value of 7.

0.

6. The method for reducing acetic acid in a succinic acid fermentation process according to claim 1, characterized in that: The seed culture step comprises the following steps: inoculating the shake flask culture solution into the seed culture medium at an inoculation rate of 0.8-1.0% by volume for seed culture, the culture time being 13-15 hours, the temperature being 35-37° C., the rotation speed being 305-314 rpm, the pressure being 0.05-0.07 MPa, the air volume being 7-9 L / min, and the pH value being controlled at 6.5-6.7 by ammonia water during the culture process to obtain the seed culture solution.

7. The method for reducing acetic acid in a succinic acid fermentation process according to claim 6, characterized in that: The seed culture medium is composed of the following ingredients: 26-30 g / L of glucose, 14-16 g / L of potassium dihydrogen phosphate, 11-13 g / L of yeast powder, 3.5-4.5 g / L of ammonium sulfate, 1.4-2.0 g / L of magnesium sulfate heptahydrate, 1.3-1.5 g / L of citric acid, 2.2-2.6 ml / L of auxiliary mixed solution, 1.2-1.4 mg / L of vitamin B1, 0.022-0.026 mg / L of riboflavin, and 0.04-0.06 mg / L of biotin.

8. The method for reducing acetic acid in a succinic acid fermentation process according to claim 7, characterized in that: The components of the auxiliary mixed solution are: 1.4-1.6 g / L of boric acid, 2.4-2.8 g / L of sodium molybdate, 3.1-3.3 g / L of nickel sulfate hexahydrate, and 4-6 g / L of manganese sulfate monohydrate.