JP2022063828A5 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel lactic acid bacterium, a method for obtaining the lactic acid bacterium, and a lactic acid bacterium-containing food or drink containing the lactic acid bacterium.

The optimal growth pH range for general lactic acid bacteria is pH 6 to 7, and the growth limit value in the acidic range is said to be pH 4, and the growth limit value in the alkaline range is said to be pH 8. However, some lactic acid bacteria have excellent acid resistance and can grow even in a harsh environment (around pH 3) where general lactic acid bacteria cannot grow (for example, Patent Documents 1 and 2).

In addition, there are lactic acid bacteria with excellent salt tolerance that can grow even in environments with high salt concentrations such as miso and soy sauce (for example, Patent Documents 3 and 4).

As described above, there are many lactic acid bacteria that can grow even in harsh environments. has not been previously reported to the applicant's knowledge.

Therefore, the present applicant believes that the presence of such lactic acid bacteria can improve the acidity and sucrose concentration of, for example, liquids obtained by mixing and squeezing plants and sugar, beverages based on this liquid, jams, fruit sauces, etc. It is possible to easily ferment materials that are difficult to ferment with general lactic acid bacteria, and it is possible to provide new fermented foods and fermented beverages. We have been researching lactic acid bacteria that can grow in low pH and high sucrose concentration.

JP 2009-225792 A WO2013/001862 JP 2007-236344 A JP 2018-42557 A

An object of the present invention is to provide lactic acid bacteria that can grow satisfactorily in a low pH and high sucrose environment.

The gist of the present invention will be described with reference to the accompanying drawings.

It relates to a lactic acid bacterium characterized by being a species belonging to the genus Lactobacillus (Lactobacillus sp.) deposited under accession number: NITE BP-03116 (identification indication: WR16-4).

The lactic acid bacterium according to claim 1 is characterized by having the base sequence of the 16S rDNA region shown in SEQ ID NO:1.

The lactic acid bacterium according to any one of claims 1 and 2 is obtained from a fermented plant extract.

The lactic acid bacterium according to claim 3, wherein the fermented plant extract is a fermented radish extract.

In the lactic acid bacterium according to claim 4, the fermented radish extract is obtained by mixing radish, white sugar and bacterial liquid and fermenting the mixture.

In addition, in the lactic acid bacterium according to claim 5, the fungus solution is composed of yeast.

In addition, the lactic acid bacterium according to any one of claims 1 to 6 grows in a low pH environment of pH 3.5 to 5.5 and grows in a high concentration sucrose environment with a sucrose concentration of 30 to 60 wt%. It relates to lactic acid bacteria characterized by

Alternatively, a fermented plant extract is added to a sterilized liquid medium to obtain a culture solution, and then this culture solution is subjected to enrichment culture to obtain an enrichment culture solution, and then this enrichment culture solution is mixed with a sterilized separation medium. A method for obtaining lactic acid bacteria, characterized by preparing a plate medium by interpreting the plate medium, and then fishing the colonies that have appeared on this plate medium to obtain lactic acid bacteria that can grow in a low-pH environment and a high-concentration sucrose environment. It is related to

Further, in the method for obtaining lactic acid bacteria according to claim 8 , the fermented plant extract is a fermented radish extract obtained by mixing and fermenting radish, white sugar, and bacterial liquid. is.

Moreover, in the method for obtaining lactic acid bacteria according to claim 9 , the bacterial solution is composed of yeast.

Further, in the method for obtaining lactic acid bacteria according to any one of claims 8 to 10 , the liquid medium contains a mixed fermented extract obtained using either one or both of a fermented vegetable extract and a fermented fruit extract, and wild grass A method for obtaining lactic acid bacteria, characterized in that an antibiotic is added to a mixture of a vegetable/superfine sugar mixture obtained by mixing a decoction and a refined sugar.

The method for obtaining lactic acid bacteria according to claim 11 , wherein the antibiotic is cycloheximide.

The present invention also relates to a lactic acid bacteria-containing food or drink, characterized by containing the lactic acid bacterium according to any one of claims 1 to 7 .

The lactic acid bacteria-containing food or drink according to claim 13 , wherein the lactic acid bacteria-containing food or drink is a fermented food or drink.

Since the lactic acid bacterium of the present invention grows (proliferates) predominantly in a low pH and high sucrose environment, it can be used, for example, as a liquid obtained by mixing and squeezing a plant and sugar, beverages based on this liquid, jams, and fruits. It is possible to easily ferment materials such as sauces that have high acidity and sucrose concentration that are difficult to ferment with common lactic acid bacteria, and to provide new fermented foods and fermented beverages.

It is a graph which shows the pH tolerance test result of Lactobacillus acidophilus JCM 1132 ^T in a present Example. 1 is a graph showing the pH tolerance test results of Lactococcus lactis subsp. lactis NBRC12007 in this example. It is a graph which shows the pH tolerance test result of Leuconostoc mesenteroides subsp. dextranicum ^NBRC100495T in a present Example. 1 is a graph showing the pH resistance test results of WR16-4 strain in this example. 1 is a graph showing the results of a sucrose tolerance test of Lactobacillus acidophilus JCM 1132 ^T in this example. 1 is a graph showing the results of a sucrose tolerance test of Lactococcus lactis subsp. lactis NBRC12007 in this example. It is a graph which shows the sucrose tolerance test result of Leuconostoc mesenteroides subsp. dextranicum ^NBRC100495T in a present Example. 1 is a graph showing the results of a sucrose tolerance test of the WR16-4 strain in this example. 4 is a table showing the composition of MRS medium in the sucrose tolerance test of this example. 4 is a table showing the composition of MRS medium in the fructose/glucose tolerance test of this example. Fig. 2 is a graph showing the results of a fructose/glucose tolerance test of the WR16-4 strain in this example. It is a data list which shows the homology search result in the gene database (NCBI) of this invention.

A preferred embodiment of the present invention will be briefly described with reference to the drawings showing the operation of the present invention.

The lactic acid bacterium of the present invention is a species belonging to the genus Lactobacillus (Lactobacillus sp.) and has been deposited under accession number: NITE BP-03116 (identification: WR16-4).

Based on the sequence data (16S rDNA sequence) obtained from the lactic acid bacterium of the present invention, a homology search was performed on the gene database of NCBI (National Center for Biotechnology Information). It is 93% (see FIG. 12), and from this result, it can be said that the lactic acid bacterium of the present invention is a new type of lactic acid bacterium (a species belonging to the genus Lactobacillus).

The lactic acid bacterium of the present invention has the characteristic of being difficult to grow at pH 6 to 7, which is generally considered to be the optimum growth environment for lactic acid bacteria, and growing well in an environment with a pH lower than this (for example, pH 3.5 to 5.5). have.

Furthermore, the lactic acid bacterium of the present invention has the characteristic of growing well even in a low pH (e.g., pH 5 or lower) and high sucrose (e.g., 30 wt% or higher) environment in which general lactic acid bacteria are difficult to grow.

As described above, the lactic acid bacteria of the present invention are characterized by superior growth in a low pH and high sucrose environment. Alternatively, it is possible to easily ferment materials such as jams and fruit sauces that have high acidity and sucrose concentration and are difficult to ferment with common lactic acid bacteria.

A specific embodiment of the present invention will be described with reference to the drawings.

The lactic acid bacterium of this example has the nucleotide sequence of the 16S rDNA region shown in SEQ ID NO: 1 and is a species belonging to the genus Lactobacillus deposited under accession number: NITE BP-03116 (identification indication: WR16-4). sp.).

The lactic acid bacteria of this example have a short rod-like cell shape, are white in the colony state, and produce extracellular polysaccharides (viscous substances).

The lactic acid bacterium (hereinafter referred to as WR16-4 strain) of this example will be described in detail below.

<Regarding the WR16-4 strain>
Based on the 16S rDNA data of the WR16-4 strain, a microorganism identification test was performed to investigate the strain of the WR16-4 strain. The microorganism identification test was commissioned to Fasmac Co., Ltd.

As a result of the microorganism identification test, the bacterial species with the highest homology value was Lactobacillus kefiri (ATCC=35441) (homology value 93.14%).

<About the novelty of the WR16-4 strain>
A homology search was performed on the NCBI gene database based on the 16S rDNA data of the WR16-4 strain to investigate the novelty of the WR16-4 strain.

FIG. 12 is a list of data showing high homology with the sample-derived sequences in this homology search. As shown in FIG. 12, even the highest homology with this WR16-4 strain was about 93%. In general, when there is no species with a homology value of 98.7% or more, it is judged to be a new species, so it can be said that this WR16-4 strain is a novel (new species) lactic acid bacterium.

<Isolation source of WR16-4 strain>
The WR16-4 strain is isolated from a fermented plant extract, specifically a fermented radish extract.

The fermented radish extract, which is the source of isolation, is obtained by mixing and fermenting radish, white sugar and fungus liquid. After fermenting the yeast fungi, the liquid obtained by pressing is further fermented and aged. Vegetables other than Japanese radish may be used as the source of separation.

<How to isolate the WR16-4 strain>
The WR16-4 strain cannot be separated from the fermented radish extract by a general separation method for lactic acid bacteria, and can be separated by the following separation method discovered by the present applicant.

(1) Add 80 μl of the above-mentioned fermented radish extract to 10 ml of liquid medium wet-sterilized (121° C., 15 minutes) and incubate at 25° C. for 6 days to obtain a culture solution.

(2) Add 80 μl of the obtained culture medium to 10 ml of the above liquid medium and incubate again at 25° C. for 3 to 4 days to obtain a culture medium.

(3) Enrichment culture is performed by repeating the treatment of 2 above several times (eight times in this example) to obtain an enrichment culture.

(4) Mix 1 ml of the enrichment culture thus obtained with 15 ml of an isolation medium that has been wet-sterilized (121° C., 15 minutes), and cool and solidify to prepare a plate.

(5) Keep the plate at 25°C for 10 days.

(6) The WR16-4 strain is obtained by picking the colonies that appear on the plate.

In addition, the liquid medium is obtained by mixing a mixed fermented extract obtained by using one or both of a fermented vegetable extract and a fermented fruit extract, a wild grass broth and white sugar. A mixture of a sucrose mixture and an antibiotic added, specifically, a wild grass obtained by mixing the above-mentioned mixed fermented extract and a boiled liquid of a plurality of wild grasses with white sugar at a ratio of 1:1. - A mixture of white sugar mixture and 1 g/L cycloheximide solution at a ratio of 10:90:1.

The above separation medium is a mixture of medium A and medium B shown in the table below after wet sterilization.

In order to confirm the characteristics of the WR16-4 strain obtained by the above isolation method, a pH tolerance test and a sucrose tolerance test were performed by comparison with common lactic acid bacteria.

Specifically, the lactic acid bacterium to be compared with the WR16-4 strain is a species belonging to a widely known genus among lactic acid bacteria, and the optimum growth pH range is pH 6 to 7, similar to general lactic acid bacteria. Lactobacillus acidophilus JCM 1132 ^T of the genus Lactobacillus, Lactococcus lactis subsp. lactis NBRC12007 of the genus Lactococcus, and Leuconostoc mesenteroides subsp. dextranicum NBRC100495 ^T of the genus Leuconostoc were used. .

<Pre-culture of each lactic acid bacterium>
In conducting the above two resistance tests, each lactic acid bacterium was precultured as follows.

(1) The MRS medium shown in FIG. 9 was prepared with 2-fold concentration. At this time, the WR16-4 strain was adjusted to pH 4.5, and the control to pH 6.5 by adding 4N sodium hydroxide solution or 4N hydrochloric acid.

(2) A 4 wt% sucrose solution or a 4 wt% glucose solution was prepared.

(3) Each of the above (1) and (2) was subjected to wet heat sterilization (121°C, 20 minutes) using an autoclave.

(4) After cooling the moist heat sterilized solutions of (1) and (2), they were mixed in a clean bench at a ratio of 1:1 (v/v) and added to MRS medium (pH 4.5) containing 2 wt% sucrose. Alternatively, an MRS medium (pH 6.5) containing 2 wt% glucose was prepared.

(5) Strain WR16-4 was cultured in MRS medium containing 2 wt% sucrose (pH 4.5) and for comparison in MRS medium containing 2 wt% glucose (pH 6.5) under anaerobic conditions at 30°C for 24-48 hours. gone.

<pH resistance test>
A pH resistance test of each precultured lactic acid bacterium was performed as follows.

(1) The MRS medium shown in FIG. 9 was prepared with 2-fold concentration. At this time, pH was adjusted to 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5 by adding 4N sodium hydroxide solution or 4N hydrochloric acid.

(2) A 4 wt% sucrose solution was prepared.

(3) Each of the above (1) and (2) was subjected to wet heat sterilization (121°C, 20 minutes) using an autoclave.

(4) After cooling the moist heat sterilized solutions of (1) and (2), they were mixed at a ratio of 1:1 (v/v) in a clean bench and mixed with MRS medium containing 2 wt% sucrose (pH 3-6. 5) was adjusted.

(5) After centrifuging each pre-cultured lactic acid strain (15,000 x g, 10 minutes) to remove the supernatant, the medium prepared in (3) has an initial concentration of A _{660 nm} ≈ 0.05 to 0. It was resuspended to 0.10.

(6) After dispensing 3 wells each (n=3) at 200 μl/well in a 96-well microplate, culture was performed at 30° C. under anaerobic conditions.

(7) Turbidity was measured over time using a microplate reader.

Figures 1 to 3 show the turbidity measurement results of lactic acid bacteria for comparison (Lactobacillus acidophilus JCM 1132 ^T (Figure 1), Lactococcus lactis subsp. lactis NBRC12007 (Figure 2), Leuconostoc mesenteroides subsp. dextranicum NBRC100495 ^T (Figure 3)). FIG. 4 is a graph showing the turbidity measurement results of the WR16-4 strain.

In the pH resistance test using 2 wt% sucrose as a carbon source, as shown in the turbidity measurement results of each lactic acid bacterium, the lactic acid bacterium for comparison grows well in an acidic region close to neutrality of pH 5 to 6.5. On the other hand, the WR16-4 strain grows in a more acidic region than the region where these lactic acid bacteria grow well, specifically in a low pH region of pH 3.5 to 5. It was confirmed that there was almost no growth in the near-neutral region with a high .

<Sucrose tolerance test>
A sucrose tolerance test of each precultured lactic acid bacterium was performed as follows.

(1) After adjusting the MRS medium shown in FIG. 4N hydrochloric acid was added to the solution to adjust the pH to 4.5.

(2) For (1) above, wet heat sterilization (121° C., 20 minutes) was performed using an autoclave.

(3) After centrifuging each precultured lactic acid strain (15,000 x g, 10 minutes) to remove the supernatant, the initial concentration in the medium adjusted in (2) is A _{660 nm} ≈ 0.05 to 0. It was resuspended to 0.10.

(4) After dispensing 3 wells each (n=3) at 200 μl/well in a 96-well microplate, culture was performed at 30° C. under anaerobic conditions.

(5) Turbidity was measured over time using a microplate reader.

Figures 5 to 8 show the turbidity measurement results of lactic acid bacteria for comparison (Lactobacillus acidophilus JCM 1132 ^T (Figure 5), Lactococcus lactis subsp. lactis NBRC12007 (Figure 6), Leuconostoc mesenteroides subsp. dextranicum NBRC100495 ^T (Figure 7)). FIG. 8 is a graph showing the turbidity measurement results of the WR16-4 strain.

In the sucrose tolerance test under acidic conditions of initial pH 4.5, as shown in the turbidity measurement results of each lactic acid bacterium, the lactic acid bacterium for comparison was confirmed to grow at a sucrose concentration of 20 wt% or less. Its growth condition (proliferation rate) was low, and it was almost impossible to grow in a high sucrose environment of 30 wt% or more. It was confirmed that it grows even in a high sucrose environment.

<Fructose/glucose tolerance test>
Sucrose is a disaccharide in which the monosaccharides fructose and glucose are combined, and it was confirmed that the WR16-4 strain can grow in a high-sucrose environment as described above. Considering that it is possible to grow in the same way as sucrose even in a fructose/glucose high concentration environment that exists in , a fructose/glucose tolerance test was performed as follows in the same manner as the above sucrose tolerance test.

(1) The MRS medium shown in FIG. 10 to which sugars such as sucrose, fructose and glucose were individually added was adjusted to a sugar concentration of 20 wt %, and then 4N hydrochloric acid was added to each to obtain a pH of 4.5. was adjusted to be

(2) Separately, the MRS medium shown in FIG. 10 to which fructose and glucose were added was adjusted so that the sugar concentration of fructose and glucose was 10 wt % (20 wt % in total), and then 4N hydrochloric acid was added to each. was added to adjust the pH to 4.5.

(3) Each of the above (1) and (2) was subjected to wet heat sterilization (121°C, 20 minutes) using an autoclave.

(4) After centrifuging the precultured strain WR16-4 (15,000×g, 10 minutes) to remove the supernatant, the initial concentration of A _{660 nm} ≈0.05 to 0.10 was added to the adjusted medium. was resuspended so that

(5) After dispensing 3 wells each (n=3) at 200 μl/well in a 96-well microplate, culture was performed at 30° C. under anaerobic conditions.

(6) Turbidity was measured over time using a microplate reader.

FIG. 11 shows the results of the above turbidity measurement in the fructose/glucose tolerance test under acidic conditions of initial pH 4.5.

As shown in FIG. 11, the WR16-4 strain has a low growth rate when either fructose or glucose is contained alone (although the growth rate is low), but when both fructose and glucose are contained, the growth rate is low. When it contains sucrose, the growth rate increases (becomes in a high growth state), and from this result, it is confirmed that the WR16-4 strain has not only sucrose tolerance but also fructose/glucose tolerance. was done.

In addition, as described above, sucrose is a disaccharide in which fructose and glucose are combined. Therefore, the WR16-4 strain contains, for example, 30 wt% each of fructose and glucose (the total sugar concentration is 60 wt%) It is considered that it can grow sufficiently even in a high sugar concentration environment.

<Use of WR16-4 strain>
The WR16-4 strain can be used for food and drink containing lactic acid bacteria, specifically fermented food and drink.

As described above, the WR16-4 strain is a lactic acid bacterium characterized by superior growth in a low pH and high sucrose environment. It is possible to easily ferment materials (acidic and high sugar concentration extracts) that are difficult to ferment with general lactic acid bacteria such as beverages, jams, fruit sauces, etc., which have high acidity and sucrose concentration. An organic acid can be contained in the extract, and effects such as imparting sourness (reducing sweetness and imparting freshness) and preserving (no need for preservatives as additives) can be obtained.

In addition, since the WR16-4 strain is a lactic acid bacterium characterized by superior growth even in a low pH and high fructose/glucose environment, in addition to the above, sugars containing both fructose and glucose (isomerized sugar, glucose and fructose, etc.).

In addition, an example of a method for obtaining the acidic and high-sugar concentration extract will be described below. Note that the method for obtaining the extract is not limited to this.

(1) Mix the cut vegetables and fruits with white sugar in the same ratio, add the bacterial solution and ferment.

(2) After fermentation, the liquid is recovered by squeezing, and the recovered liquid is further fermented and aged to obtain fermented liquid A.

(3) Fermentation liquid B is obtained by adding fermented liquid A to a wild grass boiled liquid and refined sugar, and fermenting and maturing the mixture.

The fermented liquid A and fermented liquid B become an acidic extract with a high sugar concentration. The fermented liquid A and the fermented liquid B are produced as beverages, and by fermenting with the WR16-4 strain, it imparts a sour taste and has a preservative effect without adding a preservative. It is possible to provide unprecedented beverages.

In addition, as shown in the above test results, the WR16-4 strain has the characteristic that it hardly grows in an environment of pH 6 to 7, which is the optimum pH environment for general lactic acid bacteria. When trying to ferment near-neutral materials with WR16-4 strain and other microorganisms (such as common lactic acid bacteria and yeast), WR16-4 strain does not grow until it reaches the optimum pH. Therefore, it does not inhibit the growth of other microorganisms. Therefore, it is useful when utilizing complex fermentation by multiple types of microorganisms.

In addition, from the above characteristics, the WR16-4 strain can stop fermentation without heating by adjusting the pH of the material to near neutrality, and is useful for fermented products that cannot be heated.

It should be noted that the present invention is not limited to this embodiment, and the specific configuration of each component can be appropriately designed.

NITE BP-03116

Claims (14)

A lactic acid bacterium characterized by being a species belonging to the genus Lactobacillus (Lactobacillus sp.) deposited under accession number: NITE BP-03116 (identification indication: WR16-4). 2. The lactic acid bacterium according to claim 1, wherein said lactic acid bacterium has the base sequence of the 16S rDNA region shown in SEQ ID NO:1. 3. The lactic acid bacterium according to claim 1, which is obtained from a fermented plant extract. 4. The lactic acid bacterium according to claim 3, wherein said fermented plant extract is a fermented radish extract. 5. The lactic acid bacterium according to claim 4, wherein said fermented radish extract is obtained by fermenting a mixture of radish, white sugar and bacterial solution. 6. The lactic acid bacterium according to claim 5, wherein said bacterial liquid is made of yeast. 7. The lactic acid bacterium according to any one of claims 1 to 6, wherein the lactic acid bacterium grows in a low pH environment of pH 3.5 to 5.5 and also grows in a high concentration sucrose environment of 30 to 60 wt% sucrose concentration. Lactic acid bacteria. A fermented plant extract is added to a sterilized liquid medium to obtain a culture solution, the culture solution is then enriched to obtain an enrichment culture solution, and the enrichment culture solution is then mixed with a sterilized separation medium. A method for obtaining lactic acid bacteria, characterized in that a plate medium is prepared by using the above method, and then the colonies that have appeared on this plate medium are caught to obtain lactic acid bacteria that can grow in a low-pH environment and a high-concentration sucrose environment. 9. The method for obtaining lactic acid bacteria according to claim 8 , wherein the fermented plant extract is a fermented radish extract obtained by mixing and fermenting radish, white sugar and bacterial liquid. 10. The method for obtaining lactic acid bacteria according to claim 9 , wherein said bacterial solution is made of yeast. 11. The method for obtaining lactic acid bacteria according to any one of claims 8 to 10 , wherein the liquid medium contains a mixed fermented extract obtained using either one or both of a fermented vegetable extract and a fermented fruit extract, and boiled wild grass. A method for obtaining lactic acid bacteria, characterized in that an antibiotic is added to a mixture of a vegetable/superfine sugar mixture obtained by mixing exudate and superfine sugar. 12. The method for obtaining lactic acid bacteria according to claim 11 , wherein said antibiotic is cycloheximide. A lactic acid bacteria-containing food or drink characterized by containing the lactic acid bacterium according to any one of claims 1 to 7 . 14. The food or drink containing lactic acid bacteria according to claim 13 , wherein said food or drink containing lactic acid bacteria is a fermented food or drink.