L-valine production process using microbial fermentation

Abstract

The present application relates to a method for producing L-valine, which comprises a mainculture step of culturing an L-valine-producing strain in a medium to produce L-valine, and the medium is supplied with a potassium salt.

Description

[Technical Field]

[0001] This application relates to a process technology for producing L-valine using microbial fermentation. [Background technology]

[0002] L-valine, one of the branched-chain amino acids (BCAAs), is an amino acid primarily responsible for muscle formation and development. In particular, it is a crucial amino acid that can reduce dietary crude protein levels, and is used as a feed additive. Among global feed amino acids, L-valine has seen rapid growth over the past few years in line with the trend toward reducing crude protein (CP).

[0003] According to a conventional patent (Patent Document 2), when a valine product is produced using a Corynebacterium strain with improved L-valine production ability, although a strain with improved yield is used, a fermenter with limited resources is used to produce a fermentation liquid containing L-valine, which results in a problem of limited production volume. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2016 / 0108444 [Patent Document 2] Korean Patent Registration No. 10-1721722 Summary of the Invention [Problem to be solved by the invention]

[0005] The present application provides a process technology for adding potassium salt to a culture medium in a process for producing L-valine using microbial fermentation. [Means for solving the problem]

[0006] These will be described in detail below. Note that each description and embodiment disclosed in this application also applies to other descriptions and embodiments. In other words, all combinations of various elements disclosed in this application are included in this application. Furthermore, this application is not limited to the following specific descriptions.

[0007] The present application relates to a process for producing valine using microbial fermentation, and relates to a production process in which potassium hydroxide is added to a medium during the fermentation process for producing L-valine.

[0008] FIG. 1 is a flow chart showing the method for producing L-valine according to the present application.

[0009] As shown in Figure 1, the method for producing L-valine according to the present invention includes a main culture step in which an L-valine-producing strain is cultured in a medium to produce L-valine, and the medium is supplied with potassium salt. Each step will be described in detail below.

[0010] The main culturing step is a step of preparing a fermentation broth containing L-valine using an L-valine-producing strain.

[0011] In this application, the term "fermented product" refers to the result of enzymatic or metabolic decomposition of organic substances using microorganisms. For example, the fermented product includes the culture itself obtained by culturing a microorganism in a culture medium, as well as a concentrate, dried product, or lyophilized product of the culture obtained by removing the strain from the culture. In addition, the fermented liquid may include the entire fermented product containing amino acids, or may be a fermented product containing amino acids from which impurities have been removed.

[0012] The "L-valine-producing strain" used in the main culture step includes all wild-type microorganisms and naturally or artificially genetically modified microorganisms, and may be a microorganism in which a specific mechanism has been weakened or strengthened by inserting an exogenous gene or by strengthening or inactivating the activity of an endogenous gene, and may also be a microorganism that has been genetically modified to produce a target protein or amino acid.

[0013] The L-valine-producing strain of the present application may be a microorganism that naturally has the ability to produce L-valine, or a microorganism in which the ability to produce L-valine has been imparted to a parent strain that does not have the ability to produce L-valine, but is not limited to these. Specifically, in the present application, a microorganism that produces L-valine or a target product, or a microorganism that has the ability to produce L-valine or a target product, may be a microorganism in which some of the genes in the biosynthetic pathway of the target protein or target product have been enhanced or weakened, or some of the genes in the degradation pathway of the target protein or target product have been enhanced or weakened. "Enhanced" or "improved" the L-valine-producing ability of the microorganism of the present application means that the L-valine-producing ability of the microorganism of the present application is improved compared to other microorganisms other than the microorganism of the present application, the parent strain, or an unmodified microorganism. For example, the L-valine-producing ability of the microorganism of the present application may be improved by about 1% or more, 10% or more, 100% or more, 200% or more, 500% or more, 1000% or more, 1100% or more, 1200% or more, or 1300% or more compared to that of other microorganisms, or by about 1.01-fold or more, 2-fold or more, 5-fold or more, 10-fold or more, 11-fold or more, 12-fold or more, or 13-fold or more, but is not limited to these. The term "about" refers to a range that includes ±0.5, ±0.4, ±0.3, ±0.2, ±0.1, etc., and may be any number that is equal to or in a similar range to the number following the term "about," but is not limited to these.

[0014] The microorganism used in the main culture step is at least one selected from the group consisting of the yeast Candida famata, the ascomycetes Eremothecium ashbyii and Ashbya gossypii, the bacterium Bacillus subtilis, and the genus Corynebacterium.

[0015] When the microorganism used in the main culture step is a microorganism of the genus Corynebacterium, the microorganism may be specifically selected from Corynebacterium glutamicum, Corynebacterium crudilactis, Corynebacterium deserti, Corynebacterium efficiens, Corynebacterium callunae, Corynebacterium stationis, Corynebacterium singulare, Corynebacterium halotolerans, Corynebacterium striatum, and the like. Examples of suitable microbial strains include, but are not limited to, Corynebacterium striatum, Corynebacterium ammoniagenes, Corynebacterium pollutisoli, Corynebacterium imitans, Corynebacterium testudinoris, Corynebacterium crenatum, and Corynebacterium flavescens, and more specifically Corynebacterium glutamicum.

[0016] Microorganisms of the genus Corynebacterium, particularly Corynebacterium glutamicum, are Gram-positive microorganisms that are widely used to produce L-amino acids and other useful substances. To produce these and other useful substances, various studies have been conducted to develop highly efficient production microorganisms and fermentation process technologies. For example, target-specific approaches have been primarily used, such as increasing the expression of genes encoding enzymes involved in the biosynthesis of L-tryptophan, L-valine, L-isoleucine, L-leucine, L-histidine, and L-threonine, or deleting genes unnecessary for biosynthesis. In the present application, a fermentation broth containing amino acids may be prepared using a strain of the genus Corynebacterium.

[0017] According to one embodiment of the present application, the L-valine-producing strain may be an L-valine-producing strain selected from microorganisms of the genus Corynebacterium or Escherichia, which has been transformed to enhance expression of the L-valine operon by deleting all or part of the nucleotide sequence encoding the leader peptide represented by the amino acid sequence (Met Thr Ile Ile Arg Leu Val Val Val Thr Ala Arg Arg Leu Pro) in the regulatory region of the L-valine operon. The aforementioned strains have the effect of increasing expression of acetohydroxy acid synthase, an enzyme involved in L-valine biosynthesis, thereby improving L-valine productivity.

[0018] In the main culture step, the L-valine-producing strain can be cultured under suitable culture conditions known in the art. Those skilled in the art can easily adjust the culture process depending on the strain selected. Specifically, the culture may be batch, continuous, or fed-batch culture, but is not limited thereto.

[0019] As shown in FIG. 1, potassium salt is supplied in the main culture step. In the main culture step, the potassium salt added is used to convert potassium (K + ) concentration. In some cases, adjusting the potassium concentration in the medium by adding other forms of potassium salts instead of potassium phosphate salts allows for adjustment of the potassium concentration without affecting the phosphorus (P) concentration. Potassium is known to be essential for the activity of enzymes involved in protein synthesis during microbial growth, and adjusting the potassium concentration by adding KOH can improve the efficiency of L-valine production by L-valine-producing strains. In addition, potassium is involved in the membrane potential of microorganisms, so maintaining the potassium concentration within a specific range can maintain the potential difference, which also affects the osmotic pressure of the microorganisms and ultimately affects the L-valine production efficiency.

[0020] The potassium salt used in the main culturing step may be at least one selected from the group consisting of potassium hydroxide (KOH), potassium acetate (KAc), potassium chloride (KCl), potassium sulfate (K2SO4), and potassium carbonate (K2CO3).

[0021] If the potassium ion concentration is 0.3 g / L to 6.3 g / L, the enzyme activity is increased and the membrane potential difference is maintained effectively by adding potassium, thereby ensuring high L-valine production efficiency. The potassium ion concentration may be 0.3 g / L to 6.0 g / L, 0.3 g / L to 5.5 g / L, 0.3 g / L to 5.0 g / L, 0.3 g / L to 4.5 g / L, 0.3 g / L to 4.0 g / L, 0.3 g / L to 3.5 g / L, 0.3 g / L to 3.0 g / L, or 0.3 g / L to 2.5 g / L, depending on the situation. L, 0.3g / L~2.0g / L, 0.3g / L~1.5g / L, 0.3g / L~1.0g / L, 0.3g / L~0.5g / L, 0.5g / L~ 6.3g / L, 0.5g / L~6.0g / L, 0.5g / L~5.5g / L, 0.5g / L~5.0g / L, 0.5g / L~4.5g / L, 0. 5g / L~4.0g / L, 0.5g / L~3.5g / L, 0.5g / L~3.0g / L, 0.5g / L~2.5g / L, 0.5g / L~2.0 g / L, 0.5g / L~1.5g / L, 0.5g / L~1.0g / L, 1.0g / L~6.3g / L, 1.0g / L~5.3g / L, 1.0g / L The concentration may be 1.0g / L to 4.3g / L, 1.0g / L to 3.3g / L, 1.0g / L to 2.3g / L, 2.0g / L to 6.3g / L, 2.0g / L to 5.3g / L, 3.0g / L to 6.3g / L, 4.0g / L to 6.3g / L, 5.0g / L to 6.3g / L, or 6.0g / L to 6.3g / L.

[0022] When potassium hydroxide (KOH) is used as the potassium salt, KOH may be added to the medium in the main culture step so that the concentration is 0.4 g / L to 9.0 g / L. In some cases, KOH may be added at concentrations of 0.4 g / L to 8.0 g / L, 0.4 g / L to 7.0 g / L, 0.4 g / L to 6.0 g / L, 0.4 g / L to 5.0 g / L, 0.4 g / L to 4.0 g / L, 0.4 g / L to 3.0 g / L, 0.4 g / L to 2.0 g / L, 0.4 g / L to 1.0 g / L, 1.0 g / L to 9.0 g / L, 1.0 g / L to 8.0 g / L, or 1.0 g / L to 7.0 g / L. .0g / L, 1.0g / L~6.0g / L, 1.0g / L~5.0g / L, 1.0g / L~4.0g / L, 1.0g / L~3.0g / L, 1.0g / L~2.0g / L, 2.0g / L ~9.0g / L, 2.0g / L~8.0g / L, 2.0g / L~7.0g / L, 2.0g / L~6.0g / L, 2.0g / L~5.0g / L, 2.0g / L~4.0g / L, 2.0g / L~3.0g / L, 3.0g / L~9.0g / L, 3.0g / L~8.0g / L, 3.0g / L~7.0g / L, 3.0g / L~6.0g / L, 3.0g / L~5.0g / L, 3.0g / L~4.0g / L, 4.0g / L~9.0g / L, 4.0g / L~8.0g / L, 4.0g / L~7.0g / L, 4.0g / L~6.0g / L, 4.0g / L~5.0g / L, It may be added to the medium so as to obtain a concentration of 5.0g / L to 9.0g / L, 5.0g / L to 8.0g / L, 5.0g / L to 7.0g / L, 5.0g / L to 6.0g / L, 6.0g / L to 9.0g / L, 6.0g / L to 8.0g / L, 6.0g / L to 7.0g / L, 7.0g / L to 9.0g / L, 7.0g / L to 8.0g / L, or 8.0g / L to 9.0g / L.

[0023] When potassium acetate (KAc) is used as the potassium salt, potassium acetate may be added to the medium to a concentration of 5.4 g / L to 13.0 g / L. In some cases, potassium acetate may be added to the medium to a concentration of 5.4 g / L to 11.0 g / L, 5.4 g / L to 9.0 g / L, 5.4 g / L to 7.0 g / L, 7.4 g / L to 13.0 g / L, 7.4 g / L to 11.0 g / L, 7.4 g / L to 9.0 g / L, 9.4 g / L to 13.0 g / L, 9.4 g / L to 11.0 g / L, or 11.4 g / L to 13.0 g / L.

[0024] When potassium chloride (KCl) is used as the potassium salt, potassium chloride may be added to the medium to a concentration of 4.1 g / L to 9.8 g / L. In some cases, potassium chloride may be added at concentrations of 4.1 g / L to 8.8 g / L, 4.1 g / L to 7.8 g / L, 4.1 g / L to 6.8 g / L, 4.1 g / L to 5.8 g / L, 4.1 g / L to 4.8 g / L, 5.1 g / L to 9.8 g / L, 5.1 g / L to 8.8 g / L, 5.1 g / L to 7.8 g / L, 5.1 g / L to 6.8 g / L, 5.1 g / L to 5.8 g / L, or 6. It may be added to the medium so as to obtain a concentration of 1 g / L to 9.8 g / L, 6.1 g / L to 8.8 g / L, 6.1 g / L to 7.8 g / L, 6.1 g / L to 6.8 g / L, 7.1 g / L to 9.8 g / L, 7.1 g / L to 8.8 g / L, 7.1 g / L to 7.8 g / L, 8.1 g / L to 9.8 g / L, 8.1 g / L to 8.8 g / L, or 9.1 g / L to 9.8 g / L.

[0025] When potassium sulfate (K2SO4) is used as the potassium salt, potassium sulfate may be added to the medium so that the concentration becomes 9.7 g / L to 23.0 g / L. In some cases, potassium sulfate is used in concentrations of 9.7g / L to 21.0g / L, 9.7g / L to 19.0g / L, 9.7g / L to 17.0g / L, 9.7g / L to 15.0g / L, 9.7g / L to 13.0g / L, 9.7g / L to 11.0g / L, 11.7g / L to 23.0g / L, 11.7g / L to 21.0g / L, 11.7g / L to 19.0g / L, 11.7g / L to 17.0g / L, 11.7g / L to 15.0g / L, 11.7g / L to 13.0g / L, 13.7g / L to 23.0g / L, 13.7g / L to 21.0g / L / L, 13.7g / L to 19.0g / L, 13.7g / L to 17.0g / L, 13.7g / L to 15.0g / L, 15.7g / L to 23.0g / L, 15.7g / L to 21.0g / L, 15.7g / L to 19.0g / L, 15.7g / L to 17.0g / L, 17.7g / L to 23.0g / L, 17.7g / L to 21.0g / L, 17.7g / L to 19.0g / L, 19.7g / L to 23.0g / L, 19.7g / L to 21.0g / L, or 21.7g / L to 23.0g / L.

[0026] When potassium carbonate (K2CO3) is used as the potassium salt, potassium carbonate may be added to the medium so as to have a concentration of 7.7 g / L to 18.3 g / L. In some cases, potassium carbonate may be added at concentrations of 7.7 g / L to 16.3 g / L, 7.7 g / L to 14.3 g / L, 7.7 g / L to 12.3 g / L, 7.7 g / L to 10.3 g / L, 7.7 g / L to 8.3 g / L, 9.7 g / L to 18.3 g / L, 9.7 g / L to 16.3 g / L, 9.7 g / L to 14.3 g / L, 9.7 g / L to 12.3 g / L, 9.7 g / L to 10.3 g / L, 11.7 g / L to It may be added to the medium so as to achieve a concentration of 18.3g / L, 11.7g / L to 16.3g / L, 11.7g / L to 14.3g / L, 11.7g / L to 13.3g / L, 13.7g / L to 18.3g / L, 13.7g / L to 16.3g / L, 13.7g / L to 14.3g / L, 15.7g / L to 18.3g / L, 15.7g / L to 16.3g / L, or 17.7g / L to 18.3g / L.

[0027] The potassium salt may be added before the start of the main culture or during the main culture, i.e., the potassium salt may be added to the medium in advance before the start of the main culture or may be added to the medium at an appropriate time during the main culture.

[0028] In addition, during the main culture step, bubble formation can be suppressed using an antifoaming agent such as fatty acid polyglycol ester. Here, oxygen, oxygen-containing gas, or air may be continuously injected into the culture to maintain an aerobic state. The temperature of the culture may be maintained at 20°C to 45°C. The main culture may be continued until the desired maximum amount of L-valine production is achieved. For this purpose, the main culture may be performed for 10 to 160 hours. L-valine is either excreted in the culture medium or contained in the cells.

[0029] After the main culture step, a step of separating L-valine from the fermentation broth and commercializing the separated L-valine may be further carried out.

[0030] For example, after the main culture step, the prepared fermentation broth may be concentrated to separate the L-valine wet crystals produced during the concentration process. In this process, water may be removed from the fermentation broth to precipitate L-valine in crystalline form. Concentration can be carried out by various methods. Concentration can be carried out in a conventional concentrator (e.g., a paddle dryer, a slurry dryer, a vacuum concentrator, a forced circulation concentrator, a thin film concentrator, a rotary concentrator, etc.) appropriately selected by those skilled in the art.

[0031] In addition, to separate the L-valine wet crystals precipitated by concentration from the mother liquor, a solid-liquid separator such as a vacuum membrane filtration device, a pressure membrane filtration device, or a centrifugal separator may be used, but is not limited to these.

[0032] The mother liquor remaining after the separation of the L-valine wet crystals may be reused for concentration. This allows for recycling of L-valine that does not form wet crystals or L-valine that precipitates as crystals below a certain size and remains in the mother liquor without being separated in the L-valine wet crystal separation step. Furthermore, after recycling the mother liquor, if necessary, a step such as heating the fermentation liquor may be carried out to redissolve L-valine precipitated in the form of fine crystals in the fermentation liquor.

[0033] Next, a step of preparing L-valine mixed granules may be carried out by mixing the separated L-valine wet crystals with seeds. The seeds used in this step are also called seed crystals or seed crystals and refer to substances used as catalysts for the crystallization or granulation of liquids. Specifically, the seeds in this application are amino acid crystals, such as, but not limited to, crystals of L-valine identical to the L-valine contained in the fermentation concentrate to be granulated. When the seeds come into contact with the fermentation broth, solid components present in the fermentation broth bind to the seeds to form agglomerates, thereby forming granules. The seeds used in this step may have an average particle size of 150 to 300 μm. Specifically, seeds having an average particle size of 150 to 250 μm, 200 to 300 μm, or 200 to 250 μm are used, but are not limited thereto. As mentioned above, the particle size of the seeds used ultimately affects the productivity of the granule production according to this application, and can be appropriately selected by those skilled in the art taking into account the desired moisture content, etc.

[0034] In the above step, the L-valine mixed granules may be produced using a mixing granulator. The mixing granulator may obtain granules by injecting seeds into the mixing granulator at a constant rate using a feeder while simultaneously supplying the amino acid wet crystals obtained as described above. Here, "granules" refers to macroscopic particles that are relatively large permanent aggregates formed by the aggregation of small particles such as powder, with an average particle diameter of 50 μm to 5 mm, 75 μm to 4 mm, or 100 μm to 3 mm.

[0035] Next, the L-valine mixed granules are dried to obtain an amino acid product. In the drying step, the L-valine mixed granules obtained as described above are dried, but any drying method may be used. After drying, an L-valine product is obtained. In this application, the term "L-valine product" refers to a product in which the amino acid substances contained in the fermentation broth are processed into various formulations. For example, the L-valine product may be an amino acid-containing mixture in the form of granules. However, the formulation of the L-valine product may be modified as needed without departing from the spirit of this application. Furthermore, as described above, further post-processing may be performed to achieve various formulations of the L-valine product. The L-valine product described above may be used as an additive for animal feed or for any other purpose.

[0036] Alternatively, the main culture step may be preceded by a step of flask culturing the L-valine-producing strain, followed by a step of culturing a seed culture. The flask culture and seed culture are processes for sufficiently growing microorganisms in a seed culture medium to increase the number of microorganisms required for fermentation, and can be carried out by a method commonly used in the art. By carrying out the above steps, an appropriate number of L-valine-producing strains can be directly introduced into the main culture, thereby omitting the growth process for increasing the number of L-valine-producing strains. This improves the overall efficiency of the L-valine production process.

[0037] According to one embodiment of the present application, a medium for preparing L-valine by microbial fermentation is provided.

[0038] The medium may be a composition that provides an appropriate environment for the metabolism of the L-valine-producing strain for L-valine production. The term "medium" refers to a mixture of nutrients, primarily nutrients necessary for culturing the microorganism, and provides nutrients such as water and growth factors essential for survival and growth.

[0039] The medium of the present application comprises a carbon source, a nitrogen source, a phosphorus source, and a potassium salt.

[0040] Carbon sources that can be used include carbohydrates such as glucose, fructose, sucrose, maltose, mannitol, and sorbitol; sugar alcohols; alcohols such as glycerin, pyruvic acid, lactic acid, and citric acid; organic acids; and amino acids such as glutamic acid, methionine, and lysine. Natural organic nutrient sources such as starch hydrolysates, molasses, blackstrap molasses, rice bran, cassava, bagasse, and corn steeping liquid can also be used. Specifically, carbohydrates such as glucose and sterilized pretreated molasses (i.e., molasses converted into reducing sugars) can be used. Any other carbon source can also be used in an appropriate amount. These carbon sources can be used alone or in combination of two or more.

[0041] In some cases, acetic acid may be added to the medium for valine cultivation. Acetic acid may be added to the medium as a sugar source. For example, the current acetic acid input concentration is about 9.7 g / L.

[0042] Examples of nitrogen sources that can be used include inorganic nitrogen sources such as ammonia, ammonium sulfate, ammonium chloride, ammonium acetate, ammonium phosphate, ammonium carbonate, and ammonium nitrate, and organic nitrogen sources such as amino acids such as glutamic acid, methionine, and glutamine, peptone, NZ-amine, meat extract, yeast extract, malt extract, corn steeping liquid, casein hydrolysate, fish or its degradation products, and defatted soybean cake or its degradation products. These nitrogen sources can be used alone or in combination of two or more, but are not limited to these.

[0043] Examples of the phosphorus source that can be used include potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and sodium-containing salts thereof. Examples of inorganic compounds that can be used include sodium chloride, calcium chloride, iron chloride, magnesium sulfate, iron sulfate, manganese sulfate, and calcium carbonate. Other examples include amino acids, vitamins, and / or suitable precursors. These components or precursors can be added to the medium in a batch or continuous manner, but are not limited thereto.

[0044] As described above, the concentration of potassium salt in the medium may vary depending on the type of potassium salt, and the technical significance of this has been described above.

[0045] Furthermore, it may contain essential growth substances such as vitamins and metal salts such as magnesium sulfate and iron sulfate necessary for the growth of microorganisms.

[0046] The above-mentioned raw materials may be added to the culture in a suitable manner, either batchwise or continuously, during the cultivation process. Therefore, the medium in this application refers not only to a composition added at the start of the main cultivation but also to the total of substances added during the cultivation process of the L-valine-producing strain. [Effects of the Invention]

[0047] According to the present application, in a culture method for producing L-valine, L-valine productivity (g / L / hr) is improved by additionally supplying potassium ions in the form of potassium salts in the medium. [Brief explanation of the drawings]

[0048] [Figure 1] 1 is a flowchart illustrating a method for producing L-valine according to the present application. DETAILED DESCRIPTION OF THE INVENTION

[0049] The present application will be described in more detail below with reference to examples. However, these examples are merely preferred embodiments illustrating the present application, and the present application is not limited thereto. Note that technical matters not described in this specification are well understood and easily implemented by skilled artisans in the technical field of the present application or a similar technical field.

[0050] The method for producing L-valine and the culture medium used therein according to one embodiment of the present invention have been described above. The advantageous effects of the present invention will now be described based on the experimental results of examples and comparative examples.

[0051] Experimental Example 1: Comparison of L-valine productivity (g / L / hr) at various concentrations of potassium hydroxide (KOH) added during main cultivation In one example of this application, the culture was centrifuged at low speed to remove the biomass, and the resulting supernatant was separated and analyzed by ion exchange chromatography.

[0052] [Table 1]

[0053] In Experimental Example 1, the main culture was performed with different KOH concentrations, but all other conditions, such as the culture temperature, pH, and total equivalent amount added, were the same. At a KOH concentration of 0.4 g / L (potassium concentration of 0.3 g / L), productivity increased by 3.9% compared to the culture without KOH. At a KOH concentration of 3.1 g / L (potassium concentration of 2.2 g / L), productivity increased by 8.5% compared to the culture without KOH. Furthermore, at a KOH concentration of 5.8 g / L (potassium concentration of 4.0 g / L), productivity increased by 12.1% compared to the culture without KOH. At a KOH concentration of 7.4 g / L (potassium concentration of 5.2 g / L), productivity increased by 7.6% compared to the culture without KOH. It was confirmed that productivity at each KOH concentration was improved compared to when no KOH was added. In particular, it was confirmed that valine productivity was high when the KOH concentration was within a specific range (0.4 g / L to 9.0 g / L), thereby resulting in a specific range of potassium ion concentration in the medium (0.3 g / L to 6.3 g / L), and that valine productivity was poor outside the specific range.

[0054] From the above description, those skilled in the art to which the present application pertains will understand that the present application can be implemented in other specific forms without changing the technical idea or essential features thereof. It should be understood that the above examples are merely illustrative and not limiting. The present application should be construed as including all modifications and variations derived from the meaning and scope of the claims, rather than the specification, and their equivalent concepts.

Claims

1. a mainculture step of culturing an L-valine-producing strain on a medium to produce L-valine; The method for producing L-valine, wherein the medium is supplied with a potassium salt.

2. The potassium salts include potassium hydroxide (KOH), potassium acetate (KAc), potassium chloride (KCl), potassium sulfate (K ２ SO ４ ) and potassium carbonate (K ２ CO ３ 2. The method for producing L-valine according to claim 1, wherein the L-valine is at least one selected from the group consisting of:

3. 2. The method for producing L-valine according to claim 1, wherein the potassium salt is added to the medium so that the potassium concentration is 0.3 g / L to 6.3 g / L.

4. 2. The method for producing L-valine according to claim 1, further comprising the steps of: culturing the L-valine-producing strain in a flask; and culturing an inoculum prior to the main culturing step.

5. 2. The method for producing L-valine according to claim 1, further comprising the step of concentrating the fermentation broth containing L-valine and separating the L-valine wet crystals after the main culturing step.

6. comprising a carbon source, a nitrogen source, a phosphorus source, and a potassium salt; A medium for producing L-valine by culturing an L-valine-producing strain.

7. The potassium salts include potassium hydroxide (KOH), potassium acetate (KAc), potassium chloride (KCl), potassium sulfate (K ２ SO ４ ) and potassium carbonate (K ２ CO ３ 7. The medium according to claim 6, wherein the medium is at least one selected from the group consisting of:

8. 7. The medium according to claim 6, wherein the potassium salt is added to the medium so that the potassium ion concentration is 0.3 g / L to 6.3 g / L.

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