JP4618033B2 - Method for producing food rich in γ-aminobutyric acid and γ-aminobutyric acid producing bacterium Lactobacillus carbatus KM14 - Google Patents

Description

  The present invention relates to a method for producing a food product rich in γ-aminobutyric acid (hereinafter also referred to as “GABA”), and a novel GABA-producing lactic acid bacterium used therefor.

GABA is an amino acid widely present in nature and has physiological functions such as blood pressure lowering action and tranquilizing action. GABA is produced by decarboxylation of glutamate by glutamate decarboxylase, which is an endogenous enzyme of organisms. Tea (Non-patent Document 1), germinated rice (Patent Document 1), fish soy sauce, and the like are known as foods with high production using such reactions. In addition, there is a product obtained by converting glutamic acid with lactic acid bacteria, yeasts or bacilli. These are all manufactured by adding purified glutamic acid.
In general, glutamic acid or a salt thereof is converted into GABA using a GABA-producing bacterium, a rice bran enzyme as described in Patent Document 2, or a yeast coenzyme.
However, the above report only produces GABA using purified glutamic acid as a raw material. Considering the production cost, there is a demand for a technique for producing a GABA-rich food consistently and efficiently by decomposing a high protein content to produce GABA without using purified glutamic acid.

  As microorganisms that produce GABA, aspergillus oryzae having the ability to produce glutamate decarboxylase (Patent Document 3), pure white varieties (Deposit Number: FERM P-19411) (Patent Document 4), Tempe Fungus (Patent Document 5), yeast, Lactic acid bacteria are known.

Among these, regarding Lactobacillus, in addition to Lactobacillus brevis (Patent Document 6), Patent Document 7 discloses Lactobacillus brevis TY414 (Deposit Number: FERM P-16910), Lactobacillus as lactic acid bacteria having high GABA production ability. Bacillus delbrukki bulgaricus TY393 (deposit number: FERM P-17126), Lactobacillus delbrukki bulgaricus IFO13953, Lactobacillus brevis IFO12005, etc. are disclosed.
Patent Document 8 discloses Lactobacillus hilgardy K-3 strain (deposit number: FERM P-18422) isolated from kimchi and a method for producing foods using the same.

As described above, various methods for producing a food containing GABA using GABA-producing bacteria are known.
Among these, as for using okara, in Patent Document 9, a GABA-producing bacterium is cultivated in a medium comprising a solubilized solution obtained by degrading okara with an enzyme, a protein containing glutamic acid as a constituent amino acid, and the like. And food materials containing the same are disclosed. Listed as GABA-producing bacteria are lactic acid bacteria, yeasts, fungi, Bacillus subtilis (natto), radioactive bacteria, filamentous fungi, basidiomycetes, streptococci, slime molds, photosynthetic bacteria, spore fungi, algae (chlorella), etc. Lactic acid bacteria specifically disclose Lactobacillus brevis IFO12005 in the examples.
Patent Document 10 discloses a method for producing a beverage by adding saccharides to okara and lactic acid fermentation. However, it does not enzymatically decompose okara, and lactic acid bacteria use known bacteria such as Lactobacillus acidophilus, and no description about GABA is found.

(References)
JP 2000-32923 A JP 2003-245093 A JP 2004-159612 A Japanese Patent Laid-Open No. 2005-13205 WO01 / 093696 Publication JP 2003-180389 A JP 2000-210075 A JP 2003-70462 A JP 2004-357611 A Japanese Examined Patent Publication No. 3-37904 T. Tsushida and T. Murai, Agri. Biol. Chem, 51, 2865-2871 (1987)

  An object of the present invention is to produce a GABA-rich food from not only glutamic acid but also a protein raw material containing this as a constituent amino acid. Another object of the present invention is to provide a novel GABA-producing lactic acid bacterium.

The present inventors first separated microorganisms that produce GABA efficiently in the presence of glutamic acid. And GABA producing lactic acid bacteria Lactobacillus curvatus (Lactobacillus curvatus) was isolated from food and nature.
Next, as one of the protein materials containing glutamic acid, foods rich in GABA can be obtained by adding enzymes and koji molds to heated okara, inoculating the decomposed decomposition products with the GABA-producing lactic acid bacteria, and fermenting them. I found out.
In this case, it was found that a food containing abundant GABA can be obtained without adding glutamic acid or a peptide containing glutamic acid.
And, Lactobacillus curvatus (Lactobacillus curvatus) KM14 strain having the most excellent GABA production ability among Lactobacillus curvatus was found.

That is, the present invention is characterized in that a glutamic acid-containing protein material is hydrolyzed in an aqueous system and / or a glutamic acid-containing amino acid mixture is fermented using a γ-aminobutyric acid-producing bacterium Lactobacillus curvatus. This is a method for producing a food rich in γ-aminobutyric acid.
Okara can be used as a glutamic acid-containing protein material.
As hydrolysis, acid decomposition or enzymatic decomposition can be used.
As Lactobacillus carbatus, a medium having a conversion rate from glutamic acid to γ-aminobutyric acid of 50% or more, preferably 60% or more when cultured at 30 ° C. for 2 days in a medium containing 5% by weight of glutamic acid may be used. it can.
As Lactobacillus carbatus, Lactobacillus carbatus KM14 strain (deposit number: FERM P) having a conversion rate from glutamic acid to γ-aminobutyric acid of 70% or more when cultured at 30 ° C. for 2 days in a medium containing 5% by weight of glutamic acid -20497) is more preferred.
The present invention also relates to a γ-aminobutyric acid producing bacterium Lactobacillus carbatus having a conversion rate from glutamic acid to γ-aminobutyric acid of 50% or more when cultured at 30 ° C. for 2 days in a medium containing 5% by weight of glutamic acid. is there.
The strain of Lactobacillus carbatus is a γ-aminobutyric acid producing bacterium Lactobacillus carbatus having a conversion rate of glutamic acid to γ-aminobutyric acid of 70% or more when cultured at 30 ° C. for 2 days in a medium containing 5% by weight of glutamic acid. The KM14 strain (deposit number: FERM P-20497) is preferred.

According to the present invention, foods rich in GABA can be produced from protein raw materials containing glutamic acid.
In addition, a novel GABA lactic acid bacterium Lactobacillus carbatus KM14 strain has been found according to the present invention.

  First, γ-amino characterized in that a glutamic acid-containing protein material is hydrolyzed in an aqueous system and / or a glutamic acid-containing amino acid mixture is fermented using a γ-aminobutyric acid-producing bacterium Lactobacillus curvatus. Explain how to make butyric acid-rich foods.

As the glutamic acid-containing protein material, a protein material containing a glutamic acid residue in the amino acid sequence or a protein material containing glutamic acid in the free amino acid can also be used.
Usually, if it is an edible protein raw material containing glutamic acid, it will not specifically limit. Plant proteins such as wheat, soybeans, corn and rice, and animal proteins such as avian and seafood can also be used.
Among these, wheat-derived protein materials such as wheat gluten are preferable because they are rich in glutamic acid. In this case, it is necessary to perform hydrolysis in an alkaline region.
A protein material derived from soybean is also preferable because it is rich in glutamic acid. As the protein material derived from soybean, soybean, soybean powder, defatted soybean, soybean milk or soybean milk powder, concentrated soybean protein, separated soybean protein, etc., okara containing soybean protein can be used.

Among soy protein materials, Okara is produced as a by-product during the production of processed soybean foods such as soy milk and tofu, and many of them are treated as industrial waste, so their effective use is being sought.
Okara contains proteins, carbohydrates, etc., and contains 20-30% by weight of protein. Of the amino acids constituting the protein of Okara, glutamic acid accounts for 20% by weight, and the content of glutamic acid contained in Okara is higher among soybean protein materials.
Therefore, in the present invention, it is more preferable to use okara as the glutamic acid-containing protein material.

  In the present invention, it is necessary to hydrolyze a glutamic acid-containing protein material in an aqueous system to produce glutamic acid or a peptide containing glutamic acid. This is because glutamic acid is easily converted into GABA by the lactic acid bacterium Lactobacillus carbatus used in the present invention. This is because the protein hydrolyzing ability of Lactobacillus carbatus is extremely low with the protein as it is, and it is difficult to convert it into GABA. By hydrolyzing a protein to glutamic acid or a glutamic acid-containing peptide, glutamic acid can be easily converted to GABA.

The glutamic acid-containing protein material can be easily hydrolyzed by preheating it in an aqueous system as a pretreatment for hydrolysis, and can also serve as heat sterilization.
Although the temperature in the case of heating is not particularly limited, for example, okara is usually performed at 100 to 160 ° C. for 1 to 60 minutes, and preferably at 100 to 130 ° C. for 10 to 60 minutes.
Not only is the protein in okara heat-denatured so that it can be easily hydrolyzed by enzymes, but also cellulose, hemicellulose, etc. in okara are hydrothermally decomposed to produce water-soluble hemicellulose, and the hydrolysis of okara fibers such as cellulase, which will be described later. It has the effect of facilitating the action of degrading enzymes.

As a method for hydrolyzing protein, known means can be used by acid decomposition or enzymatic decomposition, but means capable of releasing more glutamic acid is more preferable.
Proteolytic enzymes are preferred when enzymes are used for hydrolysis. Regardless of the origin of animal origin, plant origin, microbial origin, etc., any of acidic protease, neutral protease and alkaline protease may be used, but alkaline protease is wheat protein (gluten), rice protein (prolamin), corn protein (zein) Thus, it is effective not only for proteins that dissolve in an alkaline region, but also effective for soybean proteins.

  In addition, it is more effective to produce glutamic acid in combination with endo-type proteolytic enzyme and exo-type proteolytic enzyme. If an exo-type mixed proteolytic enzyme is used, even one type of commercially available enzyme is effective. “Sumiteam FP” (manufactured by Shinnippon Kagaku Kogyo Co., Ltd.) is exemplified as an end-type proteolytic enzyme, and “Umamizyme G” (manufactured by Amano Enzyme) is exemplified as an exo-type mixed protein enzyme. Can be used. Glutamic acid is not easily released only by endo-type enzymes.

If the glutamic acid-containing protein material does not contain fiber such as wheat gluten or isolated soy protein, it is not necessary to use a fiber-degrading enzyme such as cellulase, but in the case of a material containing fiber such as okara, fiber It is effective to decompose the quality because it can make the obtained food easier to eat and drink. An enzyme capable of hydrolyzing the GABA-producing bacterium of the present invention to a monosaccharide that can be assimilated as a carbon source is more preferable.
In order to promote the degradation of the fiber, it is more effective to add various esterases, xylases and the like. Other polysaccharide hydrolases can also be added.
Degradation conditions vary depending on the enzyme used and are not particularly limited, but are usually 20 to 70 ° C for 1 to 24 hours, more preferably 40 to 60 ° C for 12 to 24 hours. Moreover, pH should just be performed in the working pH range of the enzyme to be used.

The example which hydrolyzes okara with an enzyme is demonstrated more concretely.
10-30 parts (w / w ratio) of okara is dispersed with respect to 100 parts of water, more preferably 10-20 parts (w / w ratio) of okara is dispersed with respect to 100 parts of water. It is suitable to hydrolyze with enzymes.
If the ratio of okara is too large, the okara swells and the operability is deteriorated, and if the ratio of okara is too small, for example, only about 0.5 to 1.0 part of glutamic acid is eluted, resulting in poor efficiency.
By fermenting using the GABA-producing bacterium of the present invention, glutamic acid produced at the above ratio can be more efficiently converted to GABA.

  In the present invention, instead of hydrolyzing a glutamic acid-containing protein material in an aqueous system, a glutamic acid-containing amino acid mixture can be used alone or in combination with a hydrolyzate of the protein material.

In the present invention, by fermenting the above substrate with a GABA-producing bacterium Lactobacillus carbatus, although depending on the strain, glutamic acid can be highly converted to GABA and a large amount of GABA can be produced.
The GABA-producing bacterium Lactobacillus carbatus used in the present invention can be used as long as it has an ability to convert glutamic acid into GABA.
In particular, Lactobacillus carbatus having a conversion rate from glutamic acid to γ-aminobutyric acid of 50% or more, preferably 60% or more, more preferably 70% or more when cultured at 30 ° C. for 2 days in a medium containing 5% by weight of glutamic acid. Is appropriate. As a lactic acid bacterium having a conversion rate of 70% or more, Lactobacillus carbatus KM14 strain is preferable. The conversion rate can be determined by calculating the GABA concentration (%) after culturing relative to the glutamic acid concentration before culturing.

The source of separation of GABA-producing bacteria Lactobacillus carbatus can be found in pickles such as rice cake, kimchi, pickled cucumbers, Kusaya pickled juice, and sushi, where GABA is present in large quantities due to the involvement of microorganisms. Separation of the bacterial species can be performed by a known method.
After culturing this isolate, glutamate-carboxylase activity can be measured using glutamate-bromocresol green and measuring the change in pH when the carboxyl group of glutamate is decarboxylated by glutamate carboxylase (Rice , EW, CH Johnson, ME Dunnigan, and DJ Reasoner (1993) Applied and Environmental Microbiology 59 (12) 4347-4349).

According to the test of the present inventor, there were several lactic acid bacteria having high glutamate decarboxylase activity. This activity was higher than that of Lactobacillus brevis (NRIC 1032), which is generally known to be high in lactic acid bacteria and is also present in pickles.
These several lactic acid bacteria were all Lactobacillus carbatus as a result of mycological characteristics and genetic homology tests.
Furthermore, when glutamic acid was added to the medium for these several types of bacteria and the conversion rate was measured, it was revealed that one type of strain converted almost all glutamic acid into GABA.
Therefore, a strain having a particularly high activity was deposited as a γ-aminobutyric acid-producing bacterium “Lactobacillus carbatus KM14 strain” (deposit number: FERM P-20497).

Next, a specific embodiment of fermentation will be described.
A glutamic acid-containing protein material hydrolyzed in an aqueous system and / or a glutamic acid-containing amino acid mixture is a material rich in glutamic acid as described above.
By fermenting glutamic acid in this material using Lactobacillus carbatus, GABA can be produced, and a food product rich in the target GABA can be obtained.

  During fermentation, it is preferable to add sugar as a carbon source. The sugar to be added is not particularly limited as long as it is a carbon source that can assimilate Lactobacillus carbatus, but oligosaccharides are preferred because they are easily assimilated. For example, glucose, galactose, lactose, fructose, lactose, sucrose, maltose and the like can be used.

  Although the culture conditions for carrying out the fermentation of the present invention depend on the protein material used, for example, in the case of Okara, 1 to 7 days is preferred at 10 to 37 ° C. More preferably, it is 1 to 3 days at 20 to 30 ° C.

The glutamic acid-containing protein material fermented as described above can be used as a GABA-rich food as it is, preferably for sterilized after-food.
Moreover, it is also possible to clarify the culture after fermentation by filtration, concentration, activated carbon treatment or the like by a known method. For this clarification, a known method such as a filtration method using filter paper, filter cloth or the like, or centrifugation can be used.
Moreover, it is also possible to concentrate without adjusting the pH of the culture after fermentation. The concentration means is not particularly limited, and can be carried out, for example, with an evaporator or the like at a heating temperature of 70 to 90 ° C and an evaporation temperature of 40 to 60 ° C.

The obtained fermented product can be used as it is for various foods and drinks, but it is a raw material that is allowed to be added to foods and drinks, for example, sweeteners such as sugar, honey, lactose, starch syrup, various sugars, and sugar alcohols. , Fruit juice, or extracts thereof, acidulants, fragrances, minerals such as calcium, various vitamins, amino acids, polysaccharides, and the like can also be added.
Moreover, it can also sterilize by filtration sterilization, heat sterilization, etc. as needed. Moreover, it can also be filled with carbonic acid to make a carbonated beverage.
In addition, since fermented decomposed okara has many umami components, sweeteners such as miso, soy sauce, salt, vinegar, spices and sugar can be added and used as food ingredients such as seasonings.

Hereinafter, embodiments of the present invention will be described by way of examples.
[Example 1]
(Separation of lactic acid bacteria)
Five types of samples were used, including commercially available non-sterilized domestic pickles, kimchi, and pickles. Further, 10 g of cooked rice was immersed in 50 ml of ion-exchanged water and allowed to stand at room temperature for 2 weeks, and then used as a sample.
For separation of lactic acid bacteria, 1 g of a sample is appropriately diluted with physiological saline, and YPD chalk agar medium (1 wt% glucose, 0.5 wt% peptone, 1 wt% yeast extract, 0.5 wt% calcium carbonate, 1.5 wt% agar) The plate was cultured at 30 ° C. or 37 ° C. and grown from colonies.

(Detection of γ-aminobutyric acid (GABA) producing bacteria)
EWRice et al. (Rice, EW, CH Johnson, ME Dunnigan, and DJ Reasoner (1993) Applied and Environmental Microbiology 59 (12) 4347-4349).
That is, the isolated bacteria were cultured at 30 ° C. for 48 hours in a liquid medium (1 wt% glucose, 0.5 wt% peptone, 1 wt% yeast extract). The cells were collected from this culture solution by centrifugation. Further, after washing the cells with physiological saline (NaCl 0.85%), 0.6 ml of GAD (Glutamate Decarboxylase) reagent shown in Table 1 was dispensed, and after stirring, left at 30 ° C. for 72 hours. This was centrifuged to remove the cells, and the absorbance of the supernatant was measured at 660 nm.
GABA is obtained by decarboxylation from the carboxyl group of glutamic acid by GAD possessed by the microbial cell, and acts on the carboxyl group at that time, so the pH varies from acidic to neutral.
Therefore, the cultured cells were placed in a glutamic acid solution containing no sugar, and the change in pH due to decarboxylation was measured with a bromocresol green solution.

(Isolated strain)
This GAD measurement utilizes a reaction in which the pH shifts to near neutrality and the color changes from yellow to blue due to decarboxylation of glutamic acid by GAD generated by the cells. At the time of separation, colony types and shapes were grouped, and they were randomly picked. From the 15 types of strains obtained, color was observed in 4 strains, indicating the ability to produce GABA.

(Table 1) GAD reagent composition ─────────────────────
L-glutamic acid 1g
Bromocresol green 0.05g
Sodium chloride 90g
Triton X-100 (trade name) 3ml
Distilled water 1000ml
────────────────────

(Mycological characteristics of GABA-producing bacteria)
The physiological identification test was in accordance with the “Lactic Acid Bacteria Experiment Manual” (Yasuyuki Uchimura et al .: Lactic Acid Bacteria Experiment Manual -From Isolation to Identification—Asakura Shoten (1992)).
That is, Gram staining was performed by fixing cells with flame, staining with crystal violet solution, decoloring with ethanol / acetone (2: 1) mixture, drying, and microscopic examination at 1,000 times magnification. Morphology and spore formation were observed by air-drying the cells in a cover glass, fixing with a flame, staining with methylene blue solution, washing, drying, and microscopic examination at 1,000 times magnification.
A spore was considered to be spore when a colorless and transparent glowing object was observed in the stained cell.
In the catalase test, the cultured cells were collected, poured with 1 ml of 3% hydrogen peroxide, and observed for 2 to 3 minutes. At this time, those without foaming were catalase negative, and those with foaming were catalase positive.
The motility test was performed using a 0.15% agar medium with a pre-cultured test strain attached to a platinum wire. After culturing at 30 ° C for 3 days, the spread of the puncture was visually observed. In the gas generation test, a liquid medium durham tube was inserted and the presence or absence of gas generation was visually observed. In the growth temperature test, the cells were cultured at 15 ° C., 20 ° C., 40 ° C., and 45 ° C. for 3 days in a liquid medium and observed for growth.

(Table 2) Morphological characteristics of KM14 strain ───────────────
Morphological observation Short culm Sporulation None Gram staining Positive Catalase None Motility None Gas evolution None ───────────────

From the above results, it is a short gonococcus, there is no sporulation, Gram staining is positive, catalase is negative, motility and no gas generation, it is one of lactic acid bacteria that are generally widely used in food, It was a lactic acid bacterium of the genus Lactobacillus.
Next, regarding assimilation of sugar, growth was observed in a medium (1% by weight yeast extract, 0.5% by weight peptone, 1% by weight various sugars) added with the following 18 kinds of sugars. As a result, as shown in Table 3, fermentability was recognized for ribose, fructose, lactose, and mannose. However, Xylose did not show fermentability, so it became clear that it was carbatus, which proved to be a well-suited bacterial species for food.

(Table 3) Sugar assimilation of KM14 strain────────────────────────────────
Arabinose − Ribose + Xylose − Galactose +
Fructose + Mannitol − Sorbitol − Cellobiose −
Maltose − Lactose + Melibiose − Saccharose −
Trehalose − Raffinose − Mannose + Rhamnose −
Sucrose − Starch −
────────────────────────────────
(+: With assimilability,-: without assimilability)

Furthermore, microbiological classification of bacterial species by 11S ribosomal RNA was performed.
11S ribosomal RNA is a genetic sequence unique to the genus of fungi. Based on this sequence, the genus species of the bacterial species can be estimated. After culturing the cells, the DNA was extracted with phenol-chloroform according to a conventional method, and then amplified by PCR using a specific sequence present in 11s ribosomal RNA as a template. The sequence was read with a DNA sequencer. This data was compared with the type strain sequence from the database, and the homology was calculated.
From the results of 11S ribosomal RNA, there was 98% homology. In other words, the genetic sequence of KM14 strain was shown to be 98% identical to that of type strain.
In addition, as a result of mycological characteristics and genetic homology tests, it was confirmed that the four species were equivalent and were Lactobacillus carbatus. Therefore, a strain having high activity was deposited as the γ-aminobutyric acid-producing bacterium Lactobacillus carbatus KM14 strain (deposit number: FERM P-20497).

[Example 2]
(GABA production from Okara)
100 ml of distilled water was added to 10 g of Okara (manufactured by Fuji Oil Co., Ltd.) by-produced in the process of producing separated soybean protein, and heated at 120 ° C. for 20 minutes in an autoclave.
Proteolytic enzyme, Sumiteam FP (trade name, Shinnippon Chemical Co., Ltd.) and Ummamizyme G (trade name, Amano Enzyme Co., Ltd.) dissolved in 5 ml of sterilized water in heated okara dispersion are added to each 12-24 After hydrolysis at 50 ° C. for a time, solid-liquid separation was performed by centrifugation.
Moreover, the okara decomposition product which separately acid-decomposed with the hydrochloric acid to the heated okara dispersion liquid was prepared.
These Okara decomposition products were inoculated with the aforementioned “Lactobacillus carbatus KM14 strain” and cultured at 30 ° C. for 48 hours. The results are shown in Table 4.

(Table 4) Production of GABA from okara decomposition products (unit: ppm)
───────────────────────────────────
Conditions Solid content concentration (% by weight) Pre-culture glutamate Post-culture GABA
───────────────────────────────────
Enzymatic degradation 4.9 1380 1195
Acid degradation 11.5 6770 4280
───────────────────────────────────

  That is, 1195 ppm (119.5 mg / 100 ml) of enzymatic degradation products and 4280 ppm (428.0 mg / 100 ml) of GABA were produced from 10 g of okara. The conversion rate from pre-culture glutamic acid to post-culture GABA was 87% for enzymatic degradation products and 63% for acid degradation products.

Example 3 and Comparative Example
The Lactobacillus carbatus KM14 strain found in the present invention was compared with other lactic acid bacteria for the ability to produce GABA.
(Method)
Lactobacillus carbatus KM14 strain was used as a test strain, and Lactobacillus brevis NRIC 1032 was used as a control.
First, GAD (Glutamate decarboxylase) measurement of the strain was performed at 30 ° C. for 48 hours in a liquid medium (1 wt% glucose, 0.5 wt% peptone, 1 wt% yeast extract). The cells were washed with physiological saline to obtain active cells.
This is inoculated into 1 wt% glucose and 1 wt% yeast extract solution containing 1 to 5% of glutamic acid, and at 30 ° C in the same manner as Lactobacillus brevis, which is generally known to produce GABA in pickles. And cultured for 48 hours. The results are shown in Table 5.

(Table 5) Comparison of GABA productivity from glutamic acid (unit:% by weight)
─────────────────────────────────────
Strain Glutamic acid before cultivation Glutamic acid after cultivation GABA conversion rate after cultivation ──────────────────────────────────────
KM14 stock 1 0.1 0.9 90%
2 0.1 1.5 75%
5 0.1 3.5 70%
─────────────────────────────────────
Brevis stock 1 0.1 0.6 60%
2 0.9 1.0 50%
5 3.2 1.8 36%
─────────────────────────────────────

  In both strains, the GABA conversion rate tended to decrease when the glutamic acid concentration before culture was increased, but Lactobacillus carbatus KM14 produced GABA as much as 70% by weight of glutamic acid in a medium containing 5% by weight glutamic acid. And showed a high conversion rate. On the other hand, Lactobacillus brevis NRIC 1032, which is generally known as a GABA-producing bacterium such as pickles, has poor GABA productivity and a conversion rate of only 36% by weight.

According to the present invention, it was found that the lactic acid bacterium Lactobacillus carbatus was excellent in GABA production ability, and in particular, the Lactobacillus carbatus KM14 strain most excellent in GABA production ability could be found.
In addition, food containing abundant GABA can be obtained by acid-degrading or enzymatically degrading a protein-containing material that has been less effective as a by-product in the past, such as Okara, and inoculating GABA-producing lactic acid bacteria. Can now be used effectively.
The present invention makes it possible to produce a GABA-containing food from a protein material containing not only okara but also glutamic acid, and greatly contributes to the development of the industry.

Claims (2)

When a glutamic acid-containing protein material is hydrolyzed in an aqueous system and / or a glutamic acid-containing amino acid mixture is cultured at 30 ° C. for 2 days in a medium containing 5% by weight of glutamic acid,
Fermentation using Lactobacillus carbatus KM14 strain (deposit number: FERM P-20497) having the ability to produce γ-aminobutyric acid with a conversion rate from glutamic acid to γ-aminobutyric acid of 70% or more -A process for producing foods rich in aminobutyric acid. Gamma-aminobutyric acid-producing bacterium Lactobacillus carbatus KM14 (deposition number) having a conversion rate from glutamic acid to γ-aminobutyric acid of 70% or more when cultured at 30 ° C. for 2 days in a medium containing 5% by weight of glutamic acid : FERM P-20497).