Method for preparing L-valine by microbial fermentation

Abstract

The present disclosure relates to a method for preparing L-valine, comprising a main culture step of culturing an L-valine producing strain in a culture medium to produce L-valine, in which a potassium salt is provided to the culture medium.

Description

Technical Field

[0001] The present disclosure relates to a method for preparing L-valine by microbial fermentation technology. Background Art

[0002] L-valine is one of the branched-chain amino acids and is an important amino acid for muscle formation and development. L-valine is used as a feed additive, especially as a key amino acid that can reduce the dietary crude protein level. In the global feed amino acid market, L-valine has been growing rapidly in the past few years, in line with the trend of reducing crude protein (CP).

[0003] According to the existing patent (KR 10-1721722B1), in the production of valine products using a Corynebacterium strain with improved L-valine production ability, the problem is that even though a high-yield strain is used, the yield is limited due to the limited resources of the fermenter for the fermentation medium containing L-valine.

[0004] [Citation List]

[0005] [Patent Document]

[0006] Patent Document 1: US2016-0108444 A1 Summary of the Invention

[0007] [Technical Problem]

[0008] The object of the present disclosure is to provide a method for adding potassium salts to a culture medium in a method for preparing L-valine by microbial fermentation.

[0009] [Technical Solution]

[0010] This will be described in detail as follows. Each description and each embodiment disclosed in the present disclosure can also be applied to other descriptions and other embodiments respectively. That is, all combinations of various elements disclosed in the present disclosure fall within the scope of the present disclosure. In addition, the scope of the present disclosure is not limited by the following specific description.

[0011] The present disclosure relates to a method for preparing valine by microbial fermentation, and a preparation method including adding potassium hydroxide to a culture medium during the fermentation process for preparing L-valine.

[0012] Figure 1 is a flowchart illustrating the method for preparing L-valine according to the present disclosure.

[0013] Reference Figure 1, The method for preparing L-valine according to the present disclosure includes a main culture step of culturing an L-valine producing strain in a culture medium to produce L-valine, wherein a potassium salt is provided to the culture medium. Each step will be described in detail below.

[0014] The main culture step is a step of using an L-valine producing strain to prepare a fermentation culture medium containing L-valine.

[0015] The term "fermentation product" in the present disclosure may refer to the result of enzymatic or metabolic decomposition of organic substances by microorganisms. For example, the fermentation product may include the culture itself obtained by culturing microorganisms in a culture medium, or a concentrate, dried product, or lyophilized product of the culture obtained by removing the strains from the culture. In addition, in this case, the fermentation culture medium may contain all the fermentation products containing amino acids, or may be a fermentation product containing amino acids from which impurities have been removed.

[0016] The "L-valine producing strain" used in the main culture step includes wild-type microorganisms and microorganisms that have undergone natural or artificial genetic modification, which are microorganisms whose specific mechanisms have been weakened or enhanced due to reasons such as the insertion of external genes or the enhancement or inactivation of endogenous genes, and may be microorganisms with genetic modifications for producing target proteins or amino acids.

[0017] The L-valine-producing strain of the present disclosure can be, but is not limited to, a microorganism that naturally has the ability to produce L-valine, or a microorganism obtained by endowing a parent strain that does not have the ability to produce L-valine with the ability to produce L-valine. Specifically, in the present disclosure, a microorganism that produces L-valine or a target product, or has the ability to produce L-valine or a target product, can be a microorganism in which some genes in the biosynthetic pathway of the target protein or target product are strengthened or weakened, or some genes in the degradation pathway of the target protein or target product are strengthened or weakened. The "enhancement" or "increase" of the L-valine-producing ability of the microorganism of the present disclosure means that the L-valine-producing ability of the microorganism of the present disclosure is improved compared to a microorganism other than the microorganism of the present disclosure, the parent strain, or the unmodified microorganism. For example, compared with the L-valine-producing ability of other microorganisms, the microorganism of the present disclosure can have an L-valine-producing ability increased 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, and compared with the L-valine-producing ability of other microorganisms, the microorganism of the present disclosure can have an L-valine-producing ability increased by about 1.01 times or more, 2 times or more, 5 times or more, 10 times or more, 11 times or more, 12 times or more, or 13 times or more, but is not limited thereto. The term "about" includes, but is not limited to, ranges including all ±0.5, ±0.4, ±0.3, ±0.2, ±0.1, etc., and all values within a range equal to or approximate to the value after the term "about".

[0018] The above-mentioned microorganism used in the main culture step can be at least one microorganism selected from the group consisting of Candida famata, Eremothecium ashbyii and Ashbya gossypii of Ascomycetes, Bacillus subtilis, and bacteria of the genus Corynebacterium sp.

[0019] When the microorganism used in the main culture step is a microorganism belonging to the genus Corynebacterium, the microorganism may specifically be Corynebacterium glutamicum, Corynebacterium crudilactis, Corynebacterium deserti, Corynebacterium efficiens, Corynebacterium callunae, Corynebacterium stationis, Corynebacterium singulare, Corynebacterium halotolerans, Corynebacterium striatum, Corynebacterium ammoniagenes, Corynebacterium pollutisoli, Corynebacterium imitans, Corynebacterium testudinoris, Corynebacterium crenatum or Corynebacterium flavescens, more specifically Corynebacterium glutamicum, but not limited thereto.

[0020] Microorganisms belonging to the genus Corynebacterium, particularly Corynebacterium glutamicum, are Gram-positive microorganisms widely used for the production of L-amino acids and other useful substances. For the production of L-amino acids and other useful substances, many studies are being conducted to develop microorganisms and fermentation method technologies for efficient production. For example, the target substance-specific methods are mainly 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 or L-threonine, or removing genes unnecessary for biosynthesis. Similarly, in the present disclosure, a fermentation medium containing amino acids can be prepared using a strain belonging to the genus Corynebacterium.

[0021] According to an embodiment of the present disclosure, the L-valine producing strain may be an L-valine producing strain selected from microorganisms belonging to the genus Corynebacterium or microorganisms belonging to the genus Escherichia, which is transformed so as to enhance the expression of the L-valine operon by deleting the complete base sequence encoding the leader peptide or deleting or replacing a part of the base sequence, and the leader peptide is described as an amino acid sequence (Met Thr Ile Arg Leu Val Thr Ala Arg Leu Pro) in the regulatory region of the L-valine operon. The above-mentioned strain has excellent L-valine producing ability because the expression of acetohydroxy acid synthase (an enzyme involved in L-valine biosynthesis) therein is increased.

[0022] In the main culture step, the cultivation of the L-valine producing strain can be carried out under suitable culture conditions known in the art. Depending on the selected strain, those skilled in the art can easily adjust and use such a culture method. Specifically, the culture can be batch, continuous, and fed-batch culture, but is not limited thereto.

[0023] As Figure 1 disclosed in, a potassium salt is provided in the main culture step. The potassium salt added in the main culture step is used to adjust the potassium (K + ) concentration in the culture medium. In some cases, when the potassium concentration in the culture medium is adjusted by adding a potassium salt in a form other than potassium phosphate, only the potassium concentration can be adjusted without affecting the phosphorus (P) concentration. It is known that potassium is essential for the enzyme activity involved in protein synthesis during microbial growth, and adjusting the potassium concentration by adding KOH can improve the efficiency of the L-valine producing strain to produce L-valine. Since potassium is involved in the membrane potential of microorganisms, if the potassium concentration is maintained within a certain range, the potential difference can be maintained, and the maintenance of the potential difference affects the osmotic pressure of microorganisms and ultimately affects the efficiency of L-valine preparation.

[0024] The potassium salt used in the main culture step may be at least one selected from the group consisting of potassium hydroxide (KOH), potassium acetate (KAc), potassium chloride (KCl), potassium sulfate (K 2 SO 4 ) and potassium carbonate (K 2 CO 3 ).

[0025] When the potassium ion concentration is from 0.3 g / L to 6.3 g / L, the effects of increasing enzyme activity and maintaining the membrane potential difference achieved by adding potassium are excellent, and thus high L-valine production efficiency can be ensured. In some cases, the potassium ion concentration can 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, 0.3 g / L to 2.5 g / L, 0.3 g / L to 2.0 g / L, 0.3 g / L to 1.5 g / L, 0.3 g / L to 1.0 g / L, 0.3 g / L to 0.5 g / L, 0.5 g / L to 6.3 g / L, 0.5 g / L to 6.0 g / L, 0.5 g / L to 5.5 g / L, 0.5 g / L to 5.0 g / L, 0.5 g / L to 4.5 g / L, 0.5 g / L to 4.0 g / L, 0.5 g / L to 3.5 g / L, 0.5 g / L to 3.0 g / L, 0.5 g / L to 2.5 g / L, 0.5 g / L to 2.0 g / L, 0.5 g / L to 1.5 g / L, 0.5 g / L to 1.0 g / L, 1.0 g / L to 6.3 g / L, 1.0 g / L to 5.3 g / L, 1.0 g / L to 4.3 g / L, 1.0 g / L to 3.3 g / L, 1.0 g / L to 2.3 g / L, 2.0 g / L to 6.3 g / L, 2.0 g / L to 5.3 g / L, 3.0 g / L to 6.3 g / L, 4.0 g / L to 6.3 g / L, 5.0 g / L to 6.3 g / L or 6.0 g / L to 6.3 g / L.

[0026] When potassium hydroxide (KOH) is used as the potassium salt, KOH can be added such that the concentration of KOH in the medium is from 0.4 g / L to 9.0 g / L in the main culture step. In some cases, KOH can be added such that the concentration of KOH in the medium is from 0.4 g / L to 8.0 g / L, from 0.4 g / L to 7.0 g / L, from 0.4 g / L to 6.0 g / L, from 0.4 g / L to 5.0 g / L, from 0.4 g / L to 4.0 g / L, from 0.4 g / L to 3.0 g / L, from 0.4 g / L to 2.0 g / L, from 0.4 g / L to 1.0 g / L, from 1.0 g / L to 9.0 g / L, from 1.0 g / L to 8.0 g / L, from 1.0 g / L to 7.0 g / L, from 1.0 g / L to 6.0 g / L, from 1.0 g / L to 5.0 g / L, from 1.0 g / L to 4.0 g / L, from 1.0 g / L to 3.0 g / L, from 1.0 g / L to 2.0 g / L, from 2.0 g / L to 9.0 g / L, from 2.0 g / L to 8.0 g / L, from 2.0 g / L to 7.0 g / L, from 2.0 g / L to 6.0 g / L, from 2.0 g / L to 5.0 g / L, from 2.0 g / L to 4.0 g / L, from 2.0 g / L to 3.0 g / L, from 3.0 g / L to 9.0 g / L, from 3.0 g / L to 8.0 g / L, from 3.0 g / L to 7.0 g / L, from 3.0 g / L to 6.0 g / L, from 3.0 g / L to 5.0 g / L, from 3.0 g / L to 4.0 g / L, from 4.0 g / L to 9.0 g / L, from 4.0 g / L to 8.0 g / L, from 4.0 g / L to 7.0 g / L, from 4.0 g / L to 6.0 g / L, from 4.0 g / L to 5.0 g / L, from 5.0 g / L to 9.0 g / L, from 5.0 g / L to 8.0 g / L, from 5.0 g / L to 7.0 g / L, from 5.0 g / L to 6.0 g / L, from 6.0 g / L to 9.0 g / L, from 6.0 g / L to 8.0 g / L, from 6.0 g / L to 7.0 g / L, from 7.0 g / L to 9.0 g / L, from 7.0 g / L to 8.0 g / L, or from 8.0 g / L to 9.0 g / L.

[0027] When potassium acetate (KAc) is used as the potassium salt, potassium acetate can be added such that the concentration of KAc in the medium is from 5.4 g / L to 13.0 g / L. In some cases, potassium acetate can be added such that the concentration of KAc in the medium is from 5.4 g / L to 11.0 g / L, from 5.4 g / L to 9.0 g / L, from 5.4 g / L to 7.0 g / L, from 7.4 g / L to 13.0 g / L, from 7.4 g / L to 11.0 g / L, from 7.4 g / L to 9.0 g / L, from 9.4 g / L to 13.0 g / L, from 9.4 g / L to 11.0 g / L, or from 11.4 g / L to 13.0 g / L.

[0028] When potassium chloride (KCl) is used as the potassium salt, potassium chloride can be added so that the KCl concentration in the culture medium is from 4.1 g / L to 9.8 g / L. In some cases, potassium chloride can be added so that the KCl concentration in the culture medium is from 4.1 g / L to 8.8 g / L, from 4.1 g / L to 7.8 g / L, from 4.1 g / L to 6.8 g / L, from 4.1 g / L to 5.8 g / L, from 4.1 g / L to 4.8 g / L, from 5.1 g / L to 9.8 g / L, from 5.1 g / L to 8.8 g / L, from 5.1 g / L to 7.8 g / L, from 5.1 g / L to 6.8 g / L, from 5.1 g / L to 5.8 g / L, from 6.1 g / L to 9.8 g / L, from 6.1 g / L to 8.8 g / L, from 6.1 g / L to 7.8 g / L, from 6.1 g / L to 6.8 g / L, from 7.1 g / L to 9.8 g / L, from 7.1 g / L to 8.8 g / L, from 7.1 g / L to 7.8 g / L, from 8.1 g / L to 9.8 g / L, from 8.1 g / L to 8.8 g / L, or from 9.1 g / L to 9.8 g / L.

[0029] When potassium sulfate (K 2 SO 4 ) is used as the potassium salt, potassium sulfate can be added so that the K 2 SO 4 concentration in the culture medium is from 9.7 g / L to 23.0 g / L. In some cases, potassium sulfate can be added so that the K 2 SO 4 concentration in the culture medium is from 9.7 g / L to 21.0 g / L, from 9.7 g / L to 19.0 g / L, from 9.7 g / L to 17.0 g / L, from 9.7 g / L to 15.0 g / L, from 9.7 g / L to 13.0 g / L, from 9.7 g / L to 11.0 g / L, from 11.7 g / L to 23.0 g / L, from 11.7 g / L to 21.0 g / L, from 11.7 g / L to 19.0 g / L, from 11.7 g / L to 17.0 g / L, from 11.7 g / L to 15.0 g / L, from 11.7 g / L to 13.0 g / L, from 13.7 g / L to 23.0 g / L, from 13.7 g / L to 21.0 g / L, from 13.7 g / L to 19.0 g / L, from 13.7 g / L to 17.0 g / L, from 13.7 g / L to 15.0 g / L, from 15.7 g / L to 23.0 g / L, from 15.7 g / L to 21.0 g / L, from 15.7 g / L to 19.0 g / L, from 15.7 g / L to 17.0 g / L, from 17.7 g / L to 23.0 g / L, from 17.7 g / L to 21.0 g / L, from 17.7 g / L to 19.0 g / L, from 19.7 g / L to 23.0 g / L, from 19.7 g / L to 21.0 g / L, or from 21.7 g / L to 23.0 g / L.

[0030] When potassium carbonate (K 2 CO 3 ) is used as the potassium salt, potassium carbonate can be added so that the concentration of K 2 CO 3 in the culture medium is 7.7 g / L to 18.3 g / L. In some cases, potassium carbonate can be added so that the concentration of K 2 CO 3 in the culture medium is 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 18.3 g / L, 11.7 g / L to 16.3 g / L, 11.7 g / L to 14.3 g / L, 11.7 g / L to 13.3 g / L, 13.7 g / L to 18.3 g / L, 13.7 g / L to 16.3 g / L, 13.7 g / L to 14.3 g / L, 15.7 g / L to 18.3 g / L, 15.7 g / L to 16.3 g / L or 17.7 g / L to 18.3 g / L.

[0031] The potassium salt can be added before the start of the main culture or during the main culture. In other words, the potassium salt can be added to the culture medium in advance before the start of the main culture, or can be added to the culture medium at an appropriate time point during the main culture.

[0032] In the main culture step, foaming can be inhibited by using an antifoaming agent such as polyethylene glycol fatty acid ester. At this time, oxygen or an oxygen-containing gas and air can be continuously injected into the culture to maintain an aerobic state. The temperature of the culture can be maintained between 20 °C and 45 °C. The main culture can be carried out continuously until the maximum yield of L-valine required is obtained. For this purpose, the main culture can be carried out for 10 to 160 hours. L-valine can be released into the culture medium or contained in the cells.

[0033] After the main culture step is carried out, the steps of separating L-valine from the fermentation medium and the steps of commercially separating L-valine can be carried out additionally.

[0034] For example, the fermentation medium prepared after the main culture step can be concentrated, and the wet L-valine crystals produced during the concentration process can be separated. During this process, water in the fermentation medium is removed, and L-valine precipitates in crystal form. The concentration can be carried out by various methods. According to the judgment of those skilled in the art, the concentration can be carried out in a conventional concentrator (e.g., paddle dryer, slurry drying equipment, vacuum concentrator, forced circulation concentrator, thin film concentrator, or rotary concentrator).

[0035] To separate the wet L-valine 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 can be used, but the separation is not limited thereto.

[0036] The mother liquor remaining after the separation of the wet L-valine crystals can be reused for concentration. Therefore, L-valine that has not formed wet crystals or L-valine that has precipitated as crystals smaller than a certain size and remains in the mother liquor without being separated in the wet L-valine crystal separation step can be recycled. After the mother liquor is recycled, if necessary, a process such as heating the fermentation medium can be additionally carried out to redissolve the L-valine precipitated in the fermentation medium in the form of fine crystals.

[0037] Next, a step of mixing the separated wet L-valine crystals with seeds to prepare L-valine mixed particles can be carried out. The seeds used in this step are also called seed crystals and can refer to substances used as catalysts for liquid crystallization or granulation. Specifically, the seeds in the present disclosure can be, but are not limited to, amino acid crystals, for example, L-valine crystals identical to the L-valine contained in the fermentation concentrate to be granulated. When the seeds come into contact with the fermentation medium, the solid components present in the fermentation medium bind to the seeds, causing aggregation, and thus particles can be formed. The seeds used in this step can have an average particle size of 150 to 300 μm. Specifically, seeds with an average particle size of 150 to 250 μm, 200 to 300 μm, or 200 to 250 μm can be used, but the seeds are not limited thereto. The particle size of the seeds used will ultimately affect the productivity of preparing particles according to the present disclosure and can be appropriately selected by those skilled in the art by considering the required water content, etc.

[0038] In this step, a mixing granulator can be used to prepare L-valine mixed particles. The mixing granulator can feed seeds into the mixing granulator at a constant rate through a feeder while providing the previously obtained wet amino acid crystals to obtain particles. Here, a "particle" is a macroscopic particle, which is a permanent aggregate with a larger size formed by aggregating smaller particles such as powders, and can be particles with an average particle diameter of 50 μm to 5 mm, 75 μm to 4 mm, or 100 μm to 3 mm.

[0039] Next, the L-valine mixed granules can be dried to obtain an amino acid product. In the drying step, the previously obtained L-valine mixed granules are dried, and there is no limitation on the drying method. After drying, an L-valine product can be obtained. The term "L-valine product" in the present disclosure refers to a product prepared in various formulations using the amino acid substances contained in the fermentation medium. For example, the L-valine product can refer to a mixture containing amino acids in particulate form. However, if necessary, the formulation of the L-valine product can be changed without changing the inventive spirit of the present disclosure. As described above, subsequent processes can be further carried out to achieve various formulations of the L-valine product. The above-mentioned L-valine product can be used as an additive for animal feed and the like, and its application is not limited.

[0040] Meanwhile, before the main culture step, a step of culturing the L-valine producing strain in a shake flask and a subsequent seed culture step of culturing the L-valine producing strain can be carried out. Shake flask culture and seed culture are processes for sufficiently proliferating microorganisms in a seed medium to increase the number of microorganisms required for fermentation, and these processes can be carried out by ordinary methods used in the art. By carrying out the above steps, an appropriate number of L-valine producing strains can be directly used for the main culture, so the proliferation process for increasing the number of L-valine producing strains can be omitted. Therefore, the efficiency of the entire L-valine production process can be improved.

[0041] According to an embodiment of the present disclosure, a culture medium for preparing L-valine by microbial fermentation is provided.

[0042] The culture medium can be a composition that provides a suitable environment for the metabolism of the L-valine producing strain. The "culture medium" refers to a material in which nutrients required for culturing microorganisms are mixed as the main components, and it provides the nutrients and growth factors necessary for survival and development, including water.

[0043] The culture medium of the present disclosure contains a carbon source, a nitrogen source, a phosphorus source, and a potassium salt.

[0044] The carbon source can include carbohydrates such as glucose, fructose, sucrose, maltose, mannitol, and sorbitol; alcohols such as sugar alcohols and glycerol; organic acids such as pyruvic acid, lactic acid, and citric acid; amino acids such as glutamic acid, methionine, and lysine; and so on. Natural organic nutrients such as starch hydrolyzates, molasses, blackstrap molasses, rice bran, cassava, sugarcane residues, and corn steep liquor can be used. Specifically, carbohydrates such as glucose and pasteurized pretreated molasses (i.e., molasses converted into reducing sugars) can be used. Other carbon sources can be used in appropriate amounts in various ways without limitation. These carbon sources can be used alone or in combination of two or more.

[0045] In some cases, acetic acid can be added for valine fermentation. Acetic acid can be added as a carbon source to the culture medium. For example, the concentration of the added acetic acid can be about 9.7 g / L.

[0046] As the available nitrogen sources, inorganic nitrogen sources such as ammonia, ammonium sulfate, ammonium chloride, ammonium acetate, ammonium phosphate, ammonium carbonate, and ammonium nitrate can be used; and organic nitrogen sources, such as amino acids like glutamic acid, methionine, and glutamine, peptone, NZ-amine, meat extract, yeast extract, malt extract, corn steep liquor, casein hydrolysate, fish or its decomposition products, and defatted soybean cake or its decomposition products. These nitrogen sources can be used alone or in combination of two or more, but the nitrogen sources are not limited thereto.

[0047] The phosphorus sources can include potassium dihydrogen phosphate and dipotassium hydrogen phosphate, or sodium dihydrogen phosphate and disodium hydrogen phosphate. As inorganic compounds, sodium chloride, calcium chloride, ferric chloride, magnesium sulfate, ferric sulfate, manganese sulfate, calcium carbonate, etc. can be used. In addition to these, the inorganic compounds can also include amino acids, vitamins, and / or suitable precursors. These components or precursors can be added to the culture medium in a batch or continuous manner, but the addition method is not limited thereto.

[0048] As described above, the concentration of the potassium salt in the culture medium can vary depending on its type. Its technical significance is as described above.

[0049] The culture medium can also contain essential growth substances for microbial growth, such as vitamins and metal salts (such as magnesium sulfate or ferric sulfate).

[0050] During the cultivation process, raw materials can be added to the culture in a batch or continuous manner by a suitable method. Therefore, in the present disclosure, the term "culture medium" refers not only to the composition added at the start of the main culture, but also to all substances added during the cultivation of the L-valine-producing strain.

[0051] [Beneficial Effects]

[0052] According to the present disclosure, in the cultivation method for producing L-valine, the L-valine productivity (g / L / hr) is increased by additionally supplying potassium ions in the form of potassium salts to the main culture medium. Brief Description of the Drawings

[0053] Figure 1 is a flowchart illustrating the method for preparing L-valine according to the present disclosure. Detailed Description of the Embodiments

[0054] Hereinafter, the present disclosure will be described in more detail with reference to embodiments. However, the following embodiments are merely preferred embodiments for illustrating the present disclosure, and thus the scope of rights of the present disclosure is not intended to be limited thereto. At the same time, technical matters not described in this specification can be fully understood and easily implemented by those skilled in the technical field of the present disclosure or similar technical fields.

[0055] In the foregoing, a method for preparing L-valine according to an aspect of the present disclosure and a culture medium used in the method have been explained. Hereinafter, the advantageous effects mentioned in the present disclosure will be explained through the experimental results of examples and comparative examples.

[0056] Example 1 Comparison of L-valine productivity (g / L / hour) according to the concentration of potassium hydroxide (KOH) added during main culture

[0057] According to an embodiment of the present disclosure, the culture was centrifuged at a low speed to remove biomass, and the obtained supernatant was separated and analyzed by ion exchange chromatography.

[0058] [Table 1]

[0059]

[0060] In Experimental Example 1, the culture was carried out at different KOH addition concentrations during the main culture, and except for the KOH addition concentration, the culture temperature, pH, and total equivalent added were constant. Compared with when no KOH was added, when the added KOH concentration was 0.4 g / L (potassium concentration was 0.3 g / L), the productivity increased by 3.9%. Compared with when no KOH was added, when the added KOH concentration was 3.1 g / L (potassium concentration was 2.2 g / L), the productivity increased by 8.5%. Compared with when no KOH was added, when the added KOH concentration was 5.8 g / L (potassium concentration was 4.0 g / L), the productivity increased by 12.1%. Compared with when no KOH was added, when the added KOH concentration was 7.4 g / L (potassium concentration was 5.2 g / L), the productivity increased by 7.6%. Compared with when no KOH was added, at all KOH concentrations, the productivity depending on the KOH concentration increased. In particular, it has been found that when the added KOH concentration is within a specific range (0.4 g / L to 9.0 g / L), the valine productivity is high. Therefore, the concentration of potassium ions in the culture medium is within a specific range (0.3 g / L to 6.3 g / L), and when the added KOH concentration exceeds the specific range, the valine productivity decreases.

[0061] Based on the above description, those skilled in the art to which the present disclosure pertains will be able to understand that the present disclosure can be implemented in other specific forms without changing its technical idea or basic characteristics. In this regard, it should be understood that the above embodiments are exemplary in all aspects and not restrictive. The scope of the present disclosure is defined by the appended claims rather than the description following them, and thus all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included within the scope of the present disclosure.

Claims

1. A method for producing L-valine, comprising a main culture step of culturing an L-valine-producing strain in a culture medium to produce L-valine, wherein potassium salt is provided to the culture medium.

2. The method for producing L-valine according to claim 1, wherein the potassium salt is 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).

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

4. The method for producing L-valine according to claim 1, wherein a step of culturing the L-valine producing strain in a shake flask and a seed culture step of subsequently culturing the L-valine producing strain are performed, and then a main culture step is performed.

5. The method for producing L-valine according to claim 1, wherein after performing the main culturing step, a step of concentrating the fermentation medium containing L-valine and a step of separating L-valine wet crystals are additionally performed.

6. A culture medium comprising a carbon source, a nitrogen source, a phosphorus source and a potassium salt, The L-valine producing strain can be cultured in the culture medium to produce L-valine.

7. The culture medium according to claim 6, wherein the potassium salt 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).

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

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