A fermentation medium for producing terramycin

Abstract

The present application relates to the technical field of microbial fermentation, and particularly relates to a fermentation medium for producing terramycin. The fermentation medium takes corn starch-molasses-wheat hydrolysis sugar composite carbon source, bean cake powder-corn syrup-yeast extract composite nitrogen source and choline chloride-betaine-L-lysine precursor promoter as a core innovative system in a specific proportion, and further adds a morphological regulator, a defoaming agent and inorganic salts. Through the synergistic effect of multiple components, the fermentation titer and yield of terramycin are significantly improved, the fermentation period is shortened, the generation of mixed acids is effectively inhibited, and the mycelial morphology is optimized, so that the fermentation medium is suitable for industrial large-scale production of terramycin.

Description

Technical Field

[0001] This invention belongs to the field of microbial fermentation engineering and antibiotic production technology, specifically relating to a fermentation culture medium for the production of oxytetracycline. Background Technology

[0002] Oxytetracycline is an important tetracycline broad-spectrum antibiotic produced by *Streptomyces rimosus* through aerobic fermentation. It is widely used in the medical, livestock, and agricultural fields.

[0003] Currently, the industrial production of oxytetracycline still faces many challenges: 1) Low fermentation potency, resulting in high production costs; 2) Long fermentation cycle, usually requiring 160-200 hours, leading to low production efficiency; 3) During fermentation, the cell metabolism easily produces various miscellaneous acids (such as 2-acetyl-2-deamidooxytetracycline), which have structures similar to the target product, making subsequent separation and purification extremely difficult and reducing product yield and quality; 4) The mycelium is prone to aging and autolysis in the middle and late stages of fermentation, leading to premature termination of fermentation.

[0004] Existing fermentation media often use a single carbon source (such as starch) and nitrogen source (such as soybean meal or peanut meal). Furthermore, existing technologies lack components for finely regulating microbial metabolic pathways, particularly in promoting precursor supply and inhibiting the formation of heteroacids.

[0005] Therefore, developing a fermentation medium that can significantly increase oxytetracycline yield, shorten fermentation cycle, inhibit the generation of miscellaneous acids, and maintain the good physiological state of the cells has important industrial application value. Summary of the Invention

[0006] Purpose of the invention: The purpose of this invention is to address the problems of low potency, long cycle, high levels of mixed acids, and easy aging of mycelia in existing oxytetracycline fermentation technology. This invention aims to provide a novel fermentation medium that achieves precise regulation of cell metabolism through the synergistic effect of multiple components, thereby comprehensively solving the above problems.

[0007] Technical solution: A fermentation medium for producing oxytetracycline, comprising the following components: carbon source, nitrogen source, precursor promoter, inorganic salt, speciation regulator and defoamer;

[0008] The carbon source is a composite carbon source of corn starch, molasses and wheat hydrolysate;

[0009] The nitrogen source is a composite nitrogen source of soybean meal powder, corn steep liquor and yeast extract;

[0010] The precursor promoter is a mixture of choline chloride, betaine, and L-lysine hydrochloride.

[0011] Preferably, the product comprises the following components by weight / volume percentage (w / v):

[0012] Complex carbon source: corn starch 5.0%-8.0%, molasses 1.5%-3.0%, wheat hydrolysate 1.0%-2.5%;

[0013] Compound nitrogen source: soybean meal 2.0%-4.0%, corn steep liquor 1.0%-2.5%, yeast extract 0.5%-1.5%;

[0014] Precursor promoters: choline chloride 0.05%-0.15%, betaine 0.03%-0.10%, L-lysine hydrochloride 0.01%-0.05%;

[0015] Inorganic salts: calcium carbonate 0.5%-1.0%, potassium dihydrogen phosphate 0.05%-0.15%, magnesium sulfate 0.02%-0.08%;

[0016] Morphology regulator: 0.01%-0.05%;

[0017] Defoamer: 0.01%-0.05%.

[0018] Preferably, the mass ratio of corn starch, molasses and wheat hydrolysate in the composite carbon source is (5-6):(1.5-2):1.

[0019] Preferably, the mass ratio of soybean meal powder, corn steep liquor and yeast extract in the composite nitrogen source is (3-4):(1.5-2):1.

[0020] Preferably, the mass ratio of choline chloride, betaine and L-lysine hydrochloride in the precursor promoter is (3-5):(2-3):1.

[0021] Preferably, the morphology regulator is pullulan or sodium alginate.

[0022] Preferably, the defoamer is a polyether defoamer or soybean oil.

[0023] A method for preparing the fermentation medium includes the following steps:

[0024] (1) Mix the carbon source, nitrogen source, precursor promoter, inorganic salt, speciation modifier and defoamer in water in proportion and stir until completely dissolved;

[0025] (2) Adjust the pH to 6.0-7.0 using acid or alkali;

[0026] (3) Sterilize at 121℃ for 15-30 minutes to obtain the fermentation medium.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. A complex carbon source system (corn starch-molasses-wheat hydrolysate): Corn starch acts as a slow-release carbon source, providing glucose slowly through enzymatic hydrolysis. This avoids the carbon metabolism inhibition effect caused by excessively high sugar concentration in the early stages, providing stable energy and a carbon skeleton for the later stages of fermentation. Molasses is rich in sucrose, trace elements, and biotin, which can be quickly utilized by the microorganisms, promoting rapid early growth. Its organic acids help regulate the pH of the fermentation broth. Wheat hydrolysate mainly provides maltose and a small amount of glucose. Its decomposition rate is between that of corn starch and molasses, playing a crucial role in the carbon source supply. More importantly, some small peptides and amino acids in wheat hydrolysate can synergistically interact with the nitrogen source system, stimulating secondary metabolism. The three components are combined in a specific ratio to form a tiered carbon source supply model that combines fast, medium, and slow releases. This ensures a stable and balanced supply of carbon from the early to the late stages of fermentation, meeting the needs of microbial growth while continuously providing sufficient precursors and energy for oxytetracycline synthesis, effectively preventing metabolic abnormalities caused by carbon deficiency or excess.

[0029] 2. A complex nitrogen source system (soybean meal-corn steep liquor-yeast extract): Soybean meal, as an organic nitrogen source, slowly releases amino acids and peptides, serving as the primary nitrogen source for cell growth and product synthesis. Corn steep liquor is rich in soluble proteins, small peptides, amino acids, inorganic salts, and growth factors (such as biotin), which are rapidly absorbed by the cells, promoting rapid cell reproduction. Yeast extract provides abundant nucleotides, B vitamins, and glutathione, which are precursors to many coenzymes and greatly promote the metabolic activity of the cells, especially during the initiation phase of secondary metabolism. This complex nitrogen source system provides a complete nitrogen source spectrum from "rapid-acting" to "slow-acting," balancing the nitrogen requirements of cell growth and product synthesis. The key growth factors in the yeast extract complement the nutrients in the corn steep liquor and soybean meal, jointly activating the central and secondary metabolic pathways of the cells, laying the foundation for high and stable yields.

[0030] 3. Precursor system (choline chloride-betaine-L-lysine): Choline chloride, as a methyl donor, participates in the methionine cycle and phospholipid metabolism, promotes cell membrane integrity, and may affect the secondary metabolic regulatory network through methylation. Betaine is also a very effective methyl donor and, as a highly efficient osmolar protectant, can maintain the physiological activity of the cells in high-density fermentation environments. It has an additive and synergistic effect with choline chloride in the methyl donor pathway. L-lysine is one of the important precursors for the synthesis of oxytetracycline polyketide skeleton (the source of malonyl-CoA). Exogenous addition of L-lysine can "unblock" and enhance the metabolic flow to oxytetracycline synthesis. These three constitute a three-dimensional metabolic promotion network. Choline chloride and betaine together ensure the healthy physiological state and vigorous metabolic capacity of the cells, while L-lysine directly provides the "building material" for the synthesis of the target product. Their combination can significantly guide the metabolic flow to the synthesis of oxytetracycline while inhibiting the metabolic pathway leading to heteroacids, thereby increasing potency while reducing the proportion of heteroacids.

[0031] 4. Through the synergistic regulation of multiple components, this culture medium can stably achieve a fermentation potency of oxytetracycline of over 35,000 U / mL, which is about 25%-40% higher than that of traditional culture media. Due to the improved potency and shortened cycle, the volumetric yield (yield per unit volume per unit time) of oxytetracycline is significantly improved. The optimized nutrient ratio and metabolism promoter enable the cells to quickly enter the production phase and shorten the fermentation cycle to 160-170 hours. The precursor promoter system effectively inhibits the generation of impurities, reducing the impurity content in the fermentation broth by more than 20%, which greatly reduces the burden of subsequent extraction and purification, improves product quality and yield. The application of pullulan polysaccharide, a morphological regulator, enables the mycelium to form a short branching morphology more suitable for antibiotic synthesis, avoids mycelial entanglement and premature autolysis, and ensures the stability of the fermentation process. Attached Figure Description

[0032] Figure 1 This is a diagram illustrating the synergistic mechanism of the fermentation medium components in this invention.

[0033] Figure 2 This is a comparison chart of the fermentation potency of the fermentation medium of the present invention.

[0034] Figure 3 This is a comparison chart of the content of miscellaneous acids in the fermentation medium of the present invention, based on Comparative Example 1.

[0035] Figure 4 This is a comparison diagram showing the influence of variables on the fermentation medium of the present invention relative to Comparative Example 1. Detailed Implementation

[0036] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] Example 1

[0038] Culture medium composition (w / v%):

[0039] Complex carbon source: 5.0% corn starch + 1.5% molasses + 1.0% hydrolyzed wheat sugar;

[0040] Compound nitrogen source: 2.0% soybean meal powder + 1.0% corn steep liquor + 0.5% yeast extract;

[0041] Precursor promoter: choline chloride 0.05% + betaine 0.03% + L-lysine hydrochloride 0.01%;

[0042] Inorganic salts: 0.5% calcium carbonate + 0.05% potassium dihydrogen phosphate + 0.02% magnesium sulfate;

[0043] Morphology regulator: pullulan 0.01%;

[0044] Defoamer: 0.01% polyether defoamer.

[0045] Preparation steps:

[0046] 1. Dissolving and Mixing: Add approximately 70% of the process water (40℃) to the fermenter and start stirring. Add corn starch and soybean meal in sequence, stirring for 15 minutes to ensure complete suspension. Then add molasses, hydrolyzed wheat sugar, corn steep liquor, yeast extract, potassium dihydrogen phosphate, magnesium sulfate, choline chloride, betaine, L-lysine hydrochloride, and pullulan in sequence, stirring for 5 minutes after each component is added to ensure complete dissolution or uniform dispersion.

[0047] 2. pH adjustment: Precisely adjust the pH of the fermentation broth to 6.0 using a dilute sodium hydroxide solution (2 mol / L).

[0048] 3. Volume adjustment and replenishment: Add water to the final volume (5L). Finally, add calcium carbonate (to prevent precipitation) and defoamer.

[0049] 4. Sterilization: Sterilize the prepared culture medium at 121℃ for 15 minutes.

[0050] 5. Cooling inoculation: After sterilization, cool the solution to 28°C with cold water, and inoculate with 10% seed solution under aseptic conditions.

[0051] Example 2

[0052] Culture medium composition (w / v%):

[0053] Complex carbon source: 6.5% corn starch + 2.0% molasses + 1.25% hydrolyzed wheat sugar;

[0054] Compound nitrogen source: 3.0% soybean meal powder + 1.5% corn steep liquor + 0.75% yeast extract;

[0055] Precursor promoter: choline chloride 0.10% + betaine 0.065% + L-lysine hydrochloride 0.03%;

[0056] Inorganic salts: 0.75% calcium carbonate + 0.10% potassium dihydrogen phosphate + 0.05% magnesium sulfate;

[0057] Morphology regulator: pullulan 0.03%;

[0058] Defoamer: 0.03% polyether defoamer.

[0059] Preparation steps:

[0060] 1. Dissolving and Mixing: Add approximately 70% of the process water (40℃) to the fermenter and start stirring. Add corn starch and soybean meal in sequence, stirring for 15 minutes to ensure complete suspension. Then add molasses, hydrolyzed wheat sugar, corn steep liquor, yeast extract, potassium dihydrogen phosphate, magnesium sulfate, choline chloride, betaine, L-lysine hydrochloride, and pullulan in sequence, stirring for 5 minutes after each component is added to ensure complete dissolution or uniform dispersion.

[0061] 2. pH adjustment: Precisely adjust the pH of the fermentation broth to 6.5 using a dilute sodium hydroxide solution (2 mol / L).

[0062] 3. Volume adjustment and replenishment: Add water to the final volume (5L). Finally, add calcium carbonate (to prevent precipitation) and defoamer.

[0063] 4. Sterilization: Sterilize the prepared culture medium at 121℃ for 20 minutes.

[0064] 5. Cooling inoculation: After sterilization, cool the solution to 28°C with cold water, and inoculate with 10% seed solution under aseptic conditions.

[0065] Example 3

[0066] Culture medium composition (w / v%):

[0067] Complex carbon source: 8.0% corn starch + 3.0% molasses + 2.5% hydrolyzed wheat sugar;

[0068] Compound nitrogen source: 4.0% soybean meal powder + 2.5% corn steep liquor + 1.5% yeast extract;

[0069] Precursor promoter: choline chloride 0.15% + betaine 0.10% + L-lysine hydrochloride 0.05%;

[0070] Inorganic salts: Calcium carbonate 1.0% + Potassium dihydrogen phosphate 0.15% + Magnesium sulfate 0.08%;

[0071] Morphology regulator: pullulan 0.05%;

[0072] Defoamer: 0.05% polyether defoamer.

[0073] Preparation steps:

[0074] 1. Dissolving and Mixing: Add approximately 70% of the process water (40℃) to the fermenter and start stirring. Add corn starch and soybean meal in sequence, stirring for 15 minutes to ensure complete suspension. Then add molasses, hydrolyzed wheat sugar, corn steep liquor, yeast extract, potassium dihydrogen phosphate, magnesium sulfate, choline chloride, betaine, L-lysine hydrochloride, and pullulan in sequence, stirring for 5 minutes after each component is added to ensure complete dissolution or uniform dispersion.

[0075] 2. pH adjustment: Precisely adjust the pH of the fermentation broth to 7.0 using a dilute sodium hydroxide solution (2 mol / L).

[0076] 3. Volume adjustment and replenishment: Add water to the final volume (5L). Finally, add calcium carbonate (to prevent precipitation) and defoamer.

[0077] 4. Sterilization: Sterilize the prepared culture medium at 121℃ for 30 minutes.

[0078] 5. Cooling inoculation: After sterilization, cool the solution to 28°C with cold water, and inoculate with 10% seed solution under aseptic conditions.

[0079] Comparative Example 1

[0080] Fermentation medium composition (w / v%):

[0081] Carbon source: Corn starch 8.0%;

[0082] Nitrogen source: 3.5% soybean meal, 1.5% corn steep liquor;

[0083] Inorganic salts: calcium carbonate 0.8%, potassium dihydrogen phosphate 0.1%, magnesium sulfate 0.05%;

[0084] Defoamer: 0.03% polyether defoamer.

[0085] Preparation steps:

[0086] 1. Dissolving and Mixing: Add approximately 70% of the process water (40℃) to the fermenter and start stirring. Add corn starch and soybean meal powder in sequence, stirring for 15 minutes to ensure they are fully suspended. Then add corn steep liquor, potassium dihydrogen phosphate, and magnesium sulfate in sequence, stirring for 5 minutes after each component is added to ensure complete dissolution or uniform dispersion.

[0087] 2. pH adjustment: Precisely adjust the pH of the fermentation broth to 6.5 using a dilute sodium hydroxide solution (2 mol / L).

[0088] 3. Volume adjustment and replenishment: Add water to the final volume (5L). Finally, add calcium carbonate (to prevent precipitation) and defoamer.

[0089] 4. Sterilization: Sterilize the prepared culture medium at 121℃ for 20 minutes.

[0090] 5. Cooling inoculation: After sterilization, cool the solution to 28°C with cold water, and inoculate with 10% seed culture under aseptic conditions.

[0091] pH: 6.5

[0092] Sterilize: Sterilize at 121℃ for 20 minutes.

[0093] Comparative Example 2

[0094] Same as Example 2, except that the wheat hydrolysate is removed and its carbon source share is proportionally allocated to corn starch and molasses.

[0095] Comparative Example 3

[0096] Same as Example 2, except that the yeast extract is removed.

[0097] Comparative Example 4

[0098] Same as Example 2, except that all precursor promoters (choline chloride, betaine, L-lysine hydrochloride) are removed.

[0099] Comparative Example 5

[0100] Same as Example 2, except that only 0.195% L-lysine hydrochloride is added (its content is equal to the sum of the three precursor promoters in Example 2), and choline chloride and betaine are not added.

[0101] Comparative Example 6

[0102] Same as Example 2, except that pullulan is not added.

[0103] Fermentation potency was determined using the tube-disc method. Bacterial suspension was evenly spread on the surface of a medium plate, Oxford cups were placed on top, and standard solutions (with known potency) and sample diluents were added separately. The plates were incubated at 37℃ for 16–18 h, and the diameter of the inhibition zone was measured. Sample potency was calculated using a standard curve. The content of heteroacids was detected by HPLC. The chromatographic conditions were as follows: C18 reversed-phase column (4.6 mm × 250 mm, 5 μm); mobile phase: methanol-0.02 mol / L potassium dihydrogen phosphate solution (40:60 v / v); flow rate: 1.0 mL / min; detection wavelength: 210 nm (characteristic absorption peak of heteroacids in the UV region); column temperature: 30℃; injection volume: 20 μL.

[0104] Table 1 Test Results of Examples and Comparative Examples

[0105]

[0106] Example 1, using moderately low concentrations of carbon and nitrogen sources and additives, achieved a fermentation potency of 35,200 U / mL, a 25.7% improvement over Comparative Example 1, demonstrating that even at lower concentrations in the formulation system of this invention, its potency significantly surpasses that of traditional processes. Example 2, with optimized carbon and nitrogen source and additive ratios and concentrations, represents the preferred scheme, achieving the highest fermentation potency of 38,500 U / mL, a significant 37.5% improvement over Comparative Example 1, demonstrating optimal overall performance. Example 3, employing higher concentrations of carbon and nitrogen sources and additives, achieved a fermentation potency of 36,800 U / mL, a 31.4% improvement over Comparative Example 1, maintaining high-efficiency production even at high concentrations. The fermentation potency of all examples (35,200-38,500 U / mL) was significantly higher than that of Comparative Example 1 (28,000 U / mL) using the traditional culture medium, with Example 2 showing the best potency improvement of 37.5%. This improvement stems from the synergistic effect of multiple components, the multi-component synergistic mechanism of this invention being detailed in the appendix. Figure 1 The comparison results of fermentation titer, fermentation cycle, impurity acid content, and mycelial morphology of the fermentation medium of this invention are shown in the appendix. Figure 2 Appendix Figure 3And Table 1; Comparative Example 1 (traditional process) was inferior to Examples 1-3 in all aspects in terms of potency, cycle, impurity acid content, and mycelial morphology, comprehensively verifying the advanced nature of the formulation system of this invention; Comparative Example 2 (lacking wheat hydrolysate) had a lower potency (32,100 U / mL) than Example 2, proving the necessity of readily available sugar sources in the "tiered carbon source" for maintaining metabolic activity; Comparative Example 3 (lacking yeast extract) had a lower potency (30,500 U / mL) and longer mycelia, proving the importance of fast-acting nitrogen sources in the compound nitrogen source for promoting robust cell growth; Comparative Example 4 (lacking all precursor promoters) had a limited increase in potency (29,800 U / mL) and a surge in impurity acid (115%), indicating the key role of precursor promoters in improving potency and inhibiting impurity acid; Comparative Example 5 (single precursor promoter) had a potency (33,200 U / mL) The levels of both pullulan (U / mL) and miscellaneous acid control (92%) were far lower than those in Example 2, demonstrating a synergistic effect between choline chloride, betaine, and L-lysine, rather than a simple functional additive effect. Although the potency (34,900 U / mL) of Comparative Example 6 (lacking morphology regulator) was acceptable, the hyphae were severely entangled, confirming that pullulan is indispensable for maintaining normal hyphal dispersion and ensuring mass transfer and fermentation stability.

[0107] The fermentation cycle of Examples 1-3 (160-170 hours) was shortened by 20-30 hours compared to the traditional Comparative Example 1 (190 hours), resulting in a significant increase in volumetric yield (yield per unit time). The complex nitrogen source (especially corn steep liquor and yeast extract) provided fast-acting growth factors, enabling rapid cell proliferation and entry into the production phase. The optimized carbon source ratio avoided stagnation caused by substrate inhibition or scarcity. Good mycelial morphology ensured metabolic activity in the later stages of fermentation. The off-acid content of Examples 1-3 (72%-78%) was reduced by more than 22% compared to traditional culture media, with Example 2 showing a 28% reduction. This is a key manifestation of the metabolic-directing ability of this invention. A comparison chart of off-acid content in the fermentation media of this invention, based on Comparative Example 1, is attached. Figure 3In Comparative Example 4, the content of heteroacids reached as high as 115% in the absence of precursor promoters, indicating that a large amount of metabolic flux flowed to byproducts. In Comparative Example 5, even with only L-lysine added, the heteroacid content (92%) remained high, demonstrating that choline chloride and betaine, as methyl donors and osmotic protectants, played an irreplaceable role in inhibiting heteroacid formation pathways and stabilizing the cellular metabolic environment. All examples exhibited a "short branching" hyphal morphology suitable for antibiotic synthesis, while Comparative Examples 1 and 6 (lacking morphogenetic regulators) showed a "tangled" phenomenon. Although Comparative Example 6 had better potency and cycle than the traditional culture medium, its hyphal tangling led to a decrease in the mass transfer efficiency of the fermentation broth and easily caused premature autolysis of local hyphae, affecting fermentation stability. This indicates that pullulan, as a morphogenetic regulator, played a crucial role in maintaining normal hyphal morphology and ensuring a stable and controllable fermentation process. This invention comprehensively solves key technical problems in traditional oxytetracycline fermentation, such as low potency, long cycle, high levels of mixed acids, and easy mycelial aging, through the scientific design and synergistic combination of composite carbon sources, composite nitrogen sources, precursor promoters, and morphology regulators. A comparison diagram of the variable effects of the fermentation medium of this invention relative to Comparative Example 1 is attached. Figure 4 Experimental data fully demonstrate that the culture medium formulation is an organic whole, and its superior performance stems from the synergistic effect between its various systems, rather than the simple contribution of a single component, representing a significant advancement in oxytetracycline fermentation technology. The above-described embodiments merely illustrate several implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A fermentation medium for producing oxytetracycline, characterized in that, It includes the following components: carbon source, nitrogen source, precursor promoter, inorganic salt, speciation modifier and defoamer; It comprises the following components by weight / volume percentage (w / v): Carbon source: corn starch 5.0%-8.0%, molasses 1.5%-3.0%, wheat hydrolysate 1.0%-2.5%; Nitrogen source: soybean meal 2.0%-4.0%, corn steep liquor 1.0%-2.5%, yeast extract 0.5%-1.5%; Precursor promoters: choline chloride 0.05%-0.15%, betaine 0.03%-0.10%, L-lysine hydrochloride 0.01%-0.05%; Inorganic salts: calcium carbonate 0.5%-1.0%, potassium dihydrogen phosphate 0.05%-0.15%, magnesium sulfate 0.02%-0.08%; Morphology regulator: 0.01%-0.05%; Defoamer: 0.01%-0.05%; Among them, pullulan is the morphological regulator.

2. The fermentation medium for producing oxytetracycline according to claim 1, characterized in that, The mass ratio of corn starch, molasses and wheat hydrolysate in the carbon source is (5-6):(1.5-2):

1.

3. The fermentation medium for producing oxytetracycline according to claim 1, characterized in that, The mass ratio of soybean meal powder, corn steep liquor and yeast extract in the nitrogen source is (3-4):(1.5-2):

1.

4. The fermentation medium for producing oxytetracycline according to claim 1, characterized in that, The mass ratio of choline chloride, betaine and L-lysine hydrochloride in the precursor promoter is (3-5):(2-3):

1.

5. A fermentation medium for producing oxytetracycline according to claim 1, characterized in that, The defoamer is a polyether defoamer or soybean oil.

6. A method for preparing a fermentation medium as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) Mix the carbon source, nitrogen source, precursor promoter, inorganic salt, speciation modifier and defoamer in water in proportion and stir until completely dissolved; (2) Adjust the pH to 6.0-7.0 using acid or alkali; (3) Sterilize at 121℃ for 15-30 minutes to obtain the fermentation medium.

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