JP2009039080A - Soft fermented soybean (natto) and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new kind of Bacillus natto, to provide soft fermented soybean (natto), and to provide a method for producing the soft natto. <P>SOLUTION: The new kind of Bacillus natto belongs to the genus Bacillus subtilis, and has the ability to highly degrade steamed soybean cellulose. Specifically, the above Bacillus natto is Bacillus subtilis TTCC940 (Accession No. AP-21324). The soft natto is obtained by using the above Bacillus natto and containing it. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to soft natto and a method for producing the same, and more particularly to a natto bacterium having high cellulose resolving power, a method for producing soft natto using the natto bacterium, and the soft natto. The present invention produces an enzyme that highly degrades cellulose components constituting soybean seed coats and the like, and has novel natto bacteria having excellent properties as natto bacteria, and digestive absorbability and chewing using the natto bacteria A method for producing soft natto with improved properties and a natto product.

  Natto is a fermented food that uses the high nutritional value of soybeans. Protein components in raw soybeans are decomposed moderately by the action of various enzymes, including protease produced by Bacillus natto, and digestive and absorbable. Improved and unique umami ingredients are produced. In addition to its nutritional function, natto has been highly evaluated for bioregulatory functions such as thrombolytic enzymes. For this reason, natto has become one of the important foods essential for eating habits.

  Thus, natto is a food excellent in biological regulation function in addition to nutritional function. However, the digestion and absorption rate of natto is about 80%, and all of natto is digested and absorbed, and its high nutritional value is not fully utilized. Therefore, an improvement in the digestibility and absorption of natto is required.

  Moreover, in order to expand consumption of natto having the above functions, improvement of its texture and the like is required. Moreover, since the structure | tissue of the soybean which is a raw material of natto is hard, it is necessary to perform a soybean steaming process for a long time in the manufacture process of natto, and to soften soybean. However, when steaming for a long time, drainage comes out from the soybeans and the nutrients of the soybeans flow out. Therefore, in the manufacturing process of natto, it is strongly required to shorten the steaming process of soybeans or to make the conditions mild.

  Regarding the improvement of soybean cooking process and natto hardness, as prior art, for example, to improve the digestibility and absorption of natto, improve texture, shorten soybean cooking time, etc. It has been proposed to produce natto in which soybean seed coat is partially decomposed using natto bacteria having a resolution (Patent Document 1).

  Further, as another prior art, for example, in order to improve the hardness of natto and obtain a softer natto, using a specific natto strain, the softness suitable for natto for those with difficulty in chewing or for those with difficulty swallowing It has been proposed to produce natto (Patent Document 2).

JP-A-9-9903 JP 2006-67992 A

  In such a situation, in view of the above-mentioned prior art, the present inventors do not require a harsh and long soybean cooking step, improve the digestibility of natto, and improve the texture. It is an object of the present invention to provide a novel natto bacterium capable of producing natto, a method for producing natto using the same, and a soft natto product produced using the natto bacterium.

The present invention for solving the above-described problems comprises the following technical means.
(1) A Bacillus natto belonging to Bacillus subtilis, which has the cellulose resolving power of steamed soybeans.
(2) The Bacillus natto according to (1), which has cellulose resolving power of soybean seed coat.
(3) The Bacillus natto according to (1) or (2) above, wherein the Bacillus subtilis belonging to Bacillus subtilis is Bacillus subtilis TTCC940 (Bacillus subtilis TTCC940, receipt number AP-21324).
(4) A method for producing soft natto using the natto bacteria according to any one of (1) to (3) above, comprising the steps of preparing cooked soybeans from raw soybeans, and adding natto to the cooked soybeans A method for producing soft natto, comprising a step of inoculating a fungus to ferment cooked soybeans and a step of aging fermented cooked soybeans.
(5) The method for producing soft natto according to (3), wherein the natto bacteria are inoculated into the steamed soybeans and the cellulose of the steamed soybeans is decomposed by an enzyme of the natto bacteria.
(6) A soft natto produced by using the natto bacterium according to (1) or (2), wherein the cellulose of the steamed soybean is decomposed by an enzyme of the natto bacterium.
(7) A soft natto containing the natto bacteria according to any one of (1) to (3).
(8) Natto according to any one of (5) to (7), wherein the cellulose of the steamed soybean is decomposed to improve digestibility and chewability.

Next, the present invention will be described in more detail.
The present invention is a Bacillus natto belonging to Bacillus subtilis, which has a cellulose resolving power of steamed soybeans. In this invention, it is set as preferable embodiment that the said Bacillus natto has a high cellulose resolution with respect to the cellulose of a soybean seed coat. A high cellulose resolution means a cellulose resolution having a level that enables the production of soft natto.

  Further, the present invention is a method for producing soft natto using the above natto bacteria, the step of preparing steamed soybeans from raw soybeans, and inoculating the steamed soybeans with natto bacteria It comprises a step of fermenting and a step of aging fermented steamed soybeans. Aging fermented steamed soybeans means normal fermentation and aging. Soft natto means natto that is softer than, for example, a commercially available standard product (Mito tailoring), as will be described later.

  Moreover, the present invention is a soft natto produced using the above-mentioned natto bacteria, wherein the cellulose of the steamed soybean is decomposed by the enzyme of the natto bacteria. In the present invention, the natto bacterium includes the natto bacterium described above, and the cellulose of the steamed soybean is decomposed to improve digestion absorbability and chewability.

  In general, it is known that Bacillus natto does not produce enzymes that highly degrade cellulose and hemicellulose in soybean seed coat. For this reason, soybean seed coat remains in natto, which is thought to reduce the digestibility and absorption of natto. If Bacillus natto can degrade the cellulose component of soybean seed coat to a high degree, Bacillus natto obtained using the Bacillus natto is expected to be soft. And the time can be shortened.

  Therefore, the present inventors have attempted to develop a Bacillus natto having a high cellulose resolving ability that highly degrades cellulose in soybean seed coat. In order to develop a Bacillus natto having such enzyme activity, the present inventors performed a mutation treatment on a commercially available Bacillus natto or a known Bacillus natto, screened from the natural world, A Bacillus natto having high enzymatic activity with high resolution of cellulose, which decomposes cellulose highly, was obtained. Conventionally, cellulose of soybean seed coat was expected to have a strong bond and difficult to be decomposed. On the other hand, a natto bacterium that produces an enzyme having high cellulose resolution was found.

  And it became clear that natto manufactured using natto bacteria having high cellulose resolving ability was partially degraded in cellulose components such as soybean seed coat, and digestibility was improved compared to conventional products. The decomposition product of cellulose can be assimilated by natto bacteria.

  In addition, natto produced using this natto fungus is softer than conventional natto and has a preferable texture because cellulose in soybean seed coat is partially degraded. Furthermore, by using the natto bacteria, the natto bacteria decompose the cellulose in the soybean seed coat and soften the soybeans, so that it is no longer necessary to soften the soybeans by steaming for long periods under harsh conditions as before. It is possible to produce steamed soybeans by steaming for a short time or steaming under mild conditions.

  The Bacillus natto of the present invention is Bacillus natto belonging to Bacillus subtilis, and has high cellulose resolution. As such Bacillus natto, the present inventors have found a new Bacillus natto strain, named Bacillus subtilis TTCC940, and in the National Institute of Advanced Industrial Science and Technology patent biological depository center, which is a public depositary organization, in 2007 Deposited on 23 July of the year as Bacillus subtilis TTCC940, receipt number AP-21324. The bacteriological properties of the natto bacteria other than the cellulose resolution are shown below.

[Form]
Shape: Aspergillus Size: 2-3 × 1.0μm
Mobility: +
Spore formation ability: +
Spore shape: elliptical spore size: 1.4-1.6 × 0.8 μm
Spore formation site: Central Gram staining: +

[Cultural properties]
(1) Agar plate culture shape: annular surface: sticky uplift state: faulty, raised color tone: milky white gloss: yes (2) growth of liquid culture surface: fungus film formation turbidity: yes precipitation: +
(3) State of gelatin puncture culture growth: +
Gelatin liquefaction: +

[Physiological properties]
Reduction of nitrate: +
Denitrification reaction: +
VP test: +
Indole production:-
Production of hydrogen sulfide:-
Starch hydrolysis: +
Use of citric acid: +
Pigment production: −
Urease:-
Oxidase: +
Catalase: +
Growth temperature range: 15-55 ° C
Growth pH range: pH 4.1 to pH 9.5
Oxygen demand: acid and gas production from aerobic sugar Arabinose: +
Xylose: +
Glucose: +
Mannose: +
Fructose: +
Galactose:-
Maltose: +
Sucrose: +
Mannitol: +
Starch: +
Growth on Sabouraud sucrose medium: +
Casein degradation: +
Protease activity: +
γ-glutamyl transpeptidase (γ-GTP) activity: +
Growth in minimal medium:-
Biotin requirement: +
Antibiotic resistance:-
Degradation of esculin: +
Sodium chloride resistance: 1.5 mol / L or less Phage sensitivity: +

  This strain was found to be Bacillus natto from the above mycological properties. The difference between Bacillus subtilis and Bacillus subtilis other than Bacillus natto is that, while Bacillus subtilis other than Bacillus natto shows biotin-requiring and mucilage-producing ability, Is not to show. The mucilage production ability can be confirmed by a known method (Journal of Agricultural Chemistry, 37 (6), p346-350, 1963).

  In this method, steamed soybean or glutamic acid series amino acid is used as a nitrogen source, the strain is cultured in a synthetic medium (for example, GSP medium) used in combination with a carbon source, and after contacting the tip of the platinum wire to the formed colony, Pull this up and measure the length of stringing. The stringing length determined to be Bacillus natto is 50 cm or more. In addition, even if there is what has cellulase activity in Bacillus subtilis other than Bacillus natto, those that do not have the ability to produce mucilage cannot be used to produce natto. .

  The natto bacillus having high cellulose resolution according to the present invention can be obtained, for example, by performing a mutation treatment on a commercially available natto bacterium, a known natto bacterium, or a naturally isolated natto bacterium, and screening from the natural world. did it.

  Specifically, first, a commercially available natto bacterium or a known spore suspension of natto bacterium is prepared. Examples of the commercially available natto bacteria include Miyagino natto bacteria, Naruse natto bacteria, and Takahashi natto bacteria. Moreover, examples of known natto bacteria include Bacillus natto strains on which microorganisms have been deposited. And a mutation process is performed with respect to the spore suspension of these Bacillus natto. In addition to this, naturally isolated Bacillus natto collected from soil and rice straw in various places may be used.

  Examples of the sudden transition treatment include ultraviolet ray irradiation, radiation irradiation (X-ray, γ-ray), drug treatment using N-methyl-N-nitro-N-nitrosoguanidine, ethylmethanesulfonate, and the like. Next, the spore suspension subjected to the sudden change treatment is plated on a standard agar medium. Then, this was cultured at 37 ° C. for 1 to 3 days, and the formed colonies were added to a Spitzen medium (Spizizen MM medium, hereinafter referred to as “Spitzen MM medium supplemented with 1% CMC”) in which glucose was replaced with carboxymethyl cellulose (CMC). Transfer (replica). At this time, normal natto bacteria (commercially available bacteria, etc.) that became the parent strain of the mutant are also transferred (replicated) to the same CMC 1% added Spitzeizen MM medium and cultured at 37 ° C. for 1 to 3 days. The colonies formed earlier than the parent strain are screened as Bacillus natto with confirmed cellulase activity.

  Next, the screened colonies are spotted on the GSP medium, and screening is performed using the mucus production ability of the colonies as an index. This mucilage production ability can be performed by the method described above. In addition to this index for producing mucilage, it is possible to more accurately select Bacillus natto by measuring γ-GTP activity. And the natto bacteria of this invention which have a cellulose high resolution | decomposability can be obtained from the strain by which the mucilage production ability was confirmed.

  The cellulose resolution of the Bacillus natto of the present invention is based on the cellulase produced by the Bacillus natto. In the Bacillus natto of the present invention, the cellulase activity is preferably 0.8 units or more, more preferably 1.0 units or more.

  The cellulase activity of Bacillus natto is measured, for example, as follows. That is, first, a cellulase enzyme solution is prepared. As the enzyme solution, a culture solution obtained by shaking culture for 48 hours in a cellulase activity determination medium is preferably used. An example of the composition of the cellulase activity determination medium is shown below.

[Example of cellulase activity determination medium composition]
0.6g potassium dihydrogen phosphate
Dipotassium hydrogen phosphate 1.4g
Sodium citrate dihydrate 0.1g
Ammonium sulfate 0.2g
Magnesium sulfate 0.12g
100 μg of biotin
Carboxymethylcellulose 10g
(Casamino acid) 0.5g
Distilled water total 1L

  Cellulase activity can be measured by decomposing cellulose with this enzyme solution and quantifying the reducing sugar produced by the decomposition.

  An example of this method for measuring cellulase activity is the dilinitrosalicylic acid method (the method described in “Dinitrosalicylic acid method”, “Food Analysis Handbook, Tetsujiro Ohara et al., Published in 1982, Kenshisha”). This dinitrosalicylic acid method is a method for coloriating the brown color that is exhibited when the nitro group at the 3-position of dinitrosalicylic acid is reduced to an amino group by the reaction of sugar and dinitrosalicylic acid.

  Next, a method for producing natto using natto bacteria having high cellulose resolution will be described. The method for producing natto of the present invention is characterized in that in the conventional production method, natto bacteria having a high cellulose resolving power are used. That is, cooked soybeans are prepared, inoculated with natto bacteria, and then the cooked soybeans are fermented. At this time, natto bacteria having a high cellulose resolution are used. The method for inoculating the natto bacteria and the fermentation conditions are the same as in the conventional natto production method. Next, fermented steamed soybeans are refrigerated and aged to produce natto.

  In the natto thus obtained, cellulose, which is one of the main components of soybean seed coat, is decomposed better than that of conventional products in addition to the decomposition of proteins and the like in soybean by the action of the natto bacteria. Therefore, it can be determined that the natto according to the present invention is decomposed by cellulose such as soybean seed coat. In addition to this, since the natto bacteria remain in natto, the natto bacteria are collected from natto, and if the natto bacteria have a high cellulose resolving ability, it is natto according to the present invention. Can be determined.

The present invention has the following effects.
(1) The Bacillus natto of the present invention has a high cellulose resolving power for decomposing cellulose, which is one of the main components of soybean seed coat.
(2) In natto produced using this natto fungus, cellulose such as soybean seed coat is partially decomposed, so that the natto of the present invention can be expected to improve digestion and absorption compared to conventional natto. .
(3) Since a reducing sugar that can be used by Bacillus natto itself is generated by the decomposition of cellulose, the growth of Bacillus natto can be expected to be promoted.
(4) The natto of the present invention is softer than the conventional standard natto because the cellulose in the soybean seed coat is partially decomposed, has a good texture and mouthfeel, has little resistance, and can be eaten. Can be expected.
(5) Since natto bacteria partially decompose cellulose in soybean seed coat, soybean cooking time can be shortened and cooking conditions can be made milder in the production of natto. Since the efficiency is improved and the outflow of nutrients of soybean is reduced, natto with improved nutritional value can be produced.

  Next, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples.

  In this example, Bacillus natto having high cellulose resolution was selected. That is, first, a spore suspension of a commercially available natto bacterium (Miyagino natto) was prepared. This spore suspension is treated with ultraviolet rays and radiation (X-rays, γ-rays), chemical treatment using N-methyl-N-nitro-N-nitrosoguanidine, ethylmethanesulfonate, etc. Mutants were made.

  The spore suspension subjected to the mutation treatment was plated on a standard agar medium. This was cultured at 37 ° C. for 1 day, and the formed colonies were transferred (replicated) to Spitzen MM medium supplemented with 1% CMC. At this time, normal natto bacteria (commercially available bacteria, etc.) that became the parent strain of the mutant were also transferred (replicated) to the same CMC 1% added Spitzeizen MM medium and cultured at 37 ° C. for 2 days. Then, colonies formed earlier than the parent strain were screened as Bacillus natto having a high cellulase activity.

  Next, the screened colonies were spotted on the GSP medium, the colony's mucilage producing ability was inspected, and the strains that were confirmed to have mucilage producing ability were screened to obtain the desired Bacillus subtilis.

[Cellulase activity]
20 g of natto fermented with cellulose-degrading bacteria for 12 hours and 80 g of distilled water were suspended, and the supernatant was used as an enzyme solution. And carboxymethylcellulose (substrate) was decomposed | disassembled with this enzyme solution, the reducing sugar to produce | generate was quantified by the above-mentioned dinitrosalicylic acid method, and the cellulase activity was measured. The dinitrosalicylic acid method is specifically as follows.

First, a DNS reagent used for the dinitrosalicylic acid method and a cellulose substrate solution were prepared.
Liquid A: After mixing 300 ml of 4.5% sodium hydroxide solution and 800 ml of 1% dinitrosalicylic acid solution, 225 g of Rochelle salt was dissolved.
Liquid B: 10 g of crystalline phenol was added to 22 ml of 10% sodium hydroxide solution, and the volume was adjusted to 100 ml with distilled water. Thereafter, 10 g of sodium hydrogen carbonate was dissolved.

  In addition, 69 ml of B liquid was added with respect to the whole amount of A liquid made with the said mixing | blending, and it left still for 2 days, Then, it filtered, and it was set as the DNS reagent.

  Cellulose substrate solution: 1% by weight cellulose suspension was prepared using carboxymethylcellulose (manufactured by Wako).

  Next, cellulase activity was measured using the enzyme solution, DNS reagent, cellulose substrate solution, and 20 mM sodium phosphate buffer (pH 6.8) as described below.

  That is, first, 0.3 ml of 1% cellulose substrate solution and 0.4 ml of sodium phosphate buffer were added to 0.3 ml of the enzyme solution, and the reaction was performed at 40 ° C. for 30 minutes. Then, 1.5 ml of a DNS reagent was added to 0.5 ml of this reaction solution, and heated for 5 minutes in a boiling boiling bath. Thereafter, it was quenched with running water for 5 minutes, added with 8 ml of distilled water, stirred and diluted, and then allowed to stand for 20 minutes.

  The absorbance of this solution at 560 nm was measured. From this absorbance, the amount of reducing sugar was calculated in advance using a calibration curve prepared with glucose. The cellulase activity was expressed as 1 unit of the amount of enzyme that produces a reducing sugar equivalent to 1 μmol of glucose per 1 g of natto.

  The cellulase activity of the natto bacterium of the present invention and the conventional natto bacterium (our conventional bacterium) possessed by the present applicant were compared by the method described above. The result is shown in FIG. The cellulase activity of the Bacillus natto of the present invention was found to be 10% or more higher than the conventional Bacillus natto possessed by the applicant.

[Thread pulling ability]
First, a GSP agar medium having the composition shown below was prepared by a conventional method. At the time of preparing the GSP agar medium, sterilization treatment was performed at 121 ° C. for 15 minutes. Then, fungi were spotted on the GSP agar medium with a platinum wire and cultured at 37 ° C. for 24 hours. Then, the tip of the platinum wire was brought into contact with the colony formed on the GSP agar medium, and this was pulled up to measure the length of stringing.

(GSP medium composition)
Sodium glutamate 1H ₂ O: 15 g
Sucrose: 30g
Phytone: 15g
KH ₂ PO ₄ : 2.5 g
Na ₂ HPO ₄ : 1.7 g
NaCl: 0.5g
MgCl ₂ · 7H ₂ O: 0.5 g
Biotin: 100 μg
Agar: 15g
Distilled water: 1000ml

(1) Selection of natto bacteria to make natto softer (screening)
Natto bacteria were selected from the natural world and were isolated from the difference in colony shape (44 strains). Next, natto was prepared for the 44 strains isolated, and the sensory evaluation regarding the hardness of the standard stock possessed by the applicant was normally set to 4, which was very soft 1, soft 2, slightly soft 3, hard 5, Were evaluated, and those having an evaluation of 1 or 2 were selected (17 strains). Next, the selected 17 strains were subjected to sensory evaluation in three stages of A, B, and C (A is better) for natto covering, stringing, aroma, and taste, and the most excellent strain was produced as soft natto. (TTCC940) suitable for the above.

  It was found that the Bacillus natto of Example 2 (Bacillus subtilis TTCC940) has high cellulase activity and has a string drawing ability of 50 cm or more. From this, it can be said that this Bacillus natto (Bacillus subtilis TTCC940) is a novel Bacillus natto having a higher cellulase activity than the standard strain. In contrast, normal natto bacteria have low cellulase activity and are not suitable for producing soft natto. Some Bacillus subtilis other than Bacillus natto were found to have cellulase activity, but were not capable of stringing and could not be used for the production of natto.

Using the natto bacteria of Example 2 (Bacillus subtilis TTCC940), natto was prototyped as shown below. That is, first, soybeans were soaked overnight in 3 times the amount of water, and then thoroughly drained and steamed for 20 minutes under the condition of 1.8 kg / cm ² . Next, the Bacillus natto spore suspension was sprayed and stirred well so that the number of Bacillus natto bacteria was 10 ³ per 1 g of steamed soybeans. A predetermined amount of this was filled in a polystyrene foam container, covered with a polystyrene film having a small hole, and capped. And after performing a fermentation process for about 18 hours at 40 degreeC and 80% of humidity, it refrigerated at 10 degreeC for 2 days or more and made it ripen, and obtained the target natto.

  Thus, about the natto of the Example obtained, the hardness evaluation and the sensory test were done. In addition, the said hardness evaluation and sensory test were done by the method shown below.

(1) Evaluation test of the hardness of natto The evaluation test was done about the hardness of the obtained natto. The evaluation is based on 9 levels of training for the texture of the product of the present invention compared to the product of the present invention and the commercial product (Mito tailoring). The product is very hard, hard, slightly hard, the same, slightly soft, soft, and very soft. Evaluation was carried out by sensory evaluation of nine panelists. The result is shown in FIG.

(2) Sensory test Comparative evaluation was performed on the natto of Example 3 and the commercial product of the comparative example (Mito tailoring) by 51 expert panelists who tasted natto every day and were trained in the sensory test.

  From FIG. 3, it can be seen that the natto of Example 3 produced using the natto bacterium of the present invention (Bacillus subtilis TTCC940) is softer than the commercially available natto.

  Moreover, as a result of the sensory test, it was found that the natto of Example 3 had more panelists that supported the natto of Example 3 in terms of stringiness and taste than the natto of the comparative example (FIGS. 4 and 5). Moreover, regarding natto of Example 3, many opinions were expressed that it was soft, mellow, mild, smooth, and good in mouth.

  And in manufacture of the natto of Example 3, cooking time was 20 minutes and compared with manufacture of the natto of a comparative example, the cooking time could be shortened for 10 minutes.

  Next, the size of soybeans used in natto production is not uniform, and is classified into large grains, medium grains, small grains, and extremely small grains for each particle size. In addition, the present applicant also uses soybeans having a particle size of ultra-minimal grains that are smaller than the ultra-small grains. It has been found that by using the natto bacteria according to the present invention, it is possible to produce soft natto regardless of the particle size of soybean. Examples thereof are shown below.

(Large soybean)
A large soybean was used to compare natto produced by using the conventional bacteria possessed by the present applicant and the highly cellulose-degrading bacteria of the present invention. A natto was prototyped in the same manner as in Example 3 except that the soybean cooking time was 28 minutes, and the hardness of the natto was measured and compared according to the food hardness measurement method (FIG. 6). The hardness of natto produced with the conventional bacteria possessed by the present applicant was 92.2 g. In the highly cellulose-degrading bacterium of the present invention, the natto hardness was 79.6 g, indicating that it was softer.

(Medium soybean)
Using soybeans of medium grain, natto prepared using the conventional bacteria possessed by the present applicant and the highly cellulose-degrading bacteria of the present invention was compared. A natto was made in the same manner as in Example 3 except that the soybean cooking time was used as a minute. The hardness of natto produced with the conventional bacteria possessed by the present applicant was 75.9 g. In the highly cellulose-degrading bacterium of the present invention, the natto hardness was 58.2 g, indicating that it was softer.

(Small soybean)
A comparison was made between natto prepared using a conventional soybean possessed by the present applicant and a highly cellulose-degrading bacterium of the present invention using small soybeans. A natto was prototyped in the same manner as in Example 3 except that the soybean cooking time was 21 minutes. The hardness of natto produced with the conventional bacteria possessed by the present applicant was 66.7 g. In the highly cellulose-degrading bacterium of the present invention, the natto hardness was 55.1 g, indicating that it was softer.

(Very small soybean)
Using extremely small soybeans, natto produced using the conventional bacteria possessed by the present applicant and the highly cellulose-degrading bacteria of the present invention was compared. A natto was prototyped in the same manner as in Example 3 except that the soybean cooking time was 21 minutes. The hardness of natto produced with the conventional bacteria possessed by the present applicant was 51.4 g. In the highly cellulose-decomposing bacterium of the present invention, the natto hardness was 41.5 g, indicating that it was softer.

(Very small soybean)
Using ultra-small soybeans, natto produced using the conventional bacteria possessed by the present applicant and the highly cellulose-degrading bacteria of the present invention was compared. A natto was made in the same manner as in Example 3 except that the soybean cooking time was 18 minutes. The hardness of natto produced with the conventional bacteria possessed by the present applicant was 36.5 g. In the cellulose high-degrading bacterium of the present invention, the natto hardness was 27.4 g, indicating that it was softer.

  Natto can vary in hardness depending on the variety of soybean used. Natto that is too hard is not preferred, and even the present applicant cannot use soybean varieties that exceed the hardness standard and become hard natto. By using the highly cellulose-degrading bacterium of the present invention, even soybean varieties that become hard natto exceeding the standard in the normal production method can produce natto with the hardness within the standard and can be used for production. I understood.

  Using extremely small soybeans that would become hard natto, we compared natto produced using the conventional bacteria possessed by the present applicant and the cellulose-degrading bacteria of the present invention. A natto was made in the same manner as in Example 3 except that the soybean cooking time was 26 minutes. The hardness of natto produced with the conventional bacteria possessed by the present applicant was 80.3 g (the natto standard for very small soybeans in the present applicant is 80 or less). In the cellulose high-degrading bacterium of the present invention, the natto hardness was 72.3 g, and it was possible to produce natto within the standard value.

  As described above in detail, the present invention relates to a novel natto fungus, soft natto and a method for producing the same, and according to the present invention, soft natto can be produced and provided regardless of grain size and variety. it can. According to the present invention, Bacillus subtilis Bacillus natto, which has a high resolution of steamed soybean cellulose, a method for producing soft natto using the Bacillus natto, and A soft natto product produced by the method can be provided. The present invention is useful for producing and providing soft natto with improved digestibility and chewability.

The composition of the Spitzenzen MM medium and the difference in growth between the conventional Bacillus natto possessed by the applicant and the Bacillus natto of the present invention are shown. A comparison of the cellulase activity of the natto bacteria of the present invention and the conventional natto bacteria (our conventional bacteria) possessed by the present applicant is shown. The hardness evaluation by a sensory test is shown. The evaluation result of string drawing is shown. The evaluation result of taste is shown. The comparison for each soybean size (hardness data for various soybeans) is shown.

Claims (8)

  A Bacillus natto belonging to Bacillus subtilis, which has a cellulose resolving power of steamed soybeans.   The Bacillus natto according to claim 1, which has cellulose resolving power of soybean seed coat.   The Bacillus natto according to claim 1 or 2, wherein the Bacillus subtilis belonging to Bacillus subtilis is Bacillus subtilis TTCC940 (Bacillus subtilis TTCC940, receipt number AP-21324).   A method for producing soft natto using the natto bacteria according to any one of claims 1 to 3, comprising a step of preparing steamed soybeans from raw soybeans, and inoculating the steamed soybeans with natto bacteria. A method for producing soft natto, comprising a step of fermenting soybeans and a step of aging fermented steamed soybeans.   The method for producing soft natto according to claim 3, wherein the steamed soybean is inoculated with natto bacteria and the cellulose of the steamed soybean is decomposed by an enzyme of the natto bacteria.   A soft natto produced by using the Bacillus natto according to claim 1 or 2, wherein the cellulose of the steamed soybean is decomposed by an enzyme of the Bacillus natto.   A soft natto comprising the natto bacteria according to any one of claims 1 to 3.   The natto according to any one of claims 5 to 7, wherein the cellulose of the steamed soybean is decomposed to improve digestibility and chewability.