JP2000060535A - Preservation of microorganismal cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition capable of preserving microorganismal cells over an extended period by a simple treatment means without the need of any cumbersome process such as drying or freezing by incorporating the microorganismal cells with a compound functioning to lower the moisture activity of the cells. SOLUTION: This composition comprises microorganismal cells and a compound functioning to lower the moisture activity of the cells (hereafter called as compound); wherein the microorganismal cells is pref. those used in foods such as yeast cells or lactic acid bacteria; the above compound is pref. starch, esp. dry starch; the amount of the compound to be incorporated is pref. 0.5-5 pts.wt. per pt.wt. of the microorganismal cells; the moisture activity of this composition is pref. 0.6-0.8; when the compound is starch, its content in the composition is pref. 70-80 wt.%; and it is preferable that this composition is preserved in a closed vessel at 1-10 deg.C.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for preserving microbial cells used for fermentation of foods, a composition containing microbial cells having improved storability, and a method for producing the same.

[0002]

2. Description of the Related Art When microbial cells having a biological activity such as yeast, lactic acid bacterium, acetic acid bacterium, etc. are used for the production of foods, etc., a squeezed microbial cell obtained by squeezing the cells in a culture solution and then squeezing them. Body or dried microbial cells obtained by drying the pressed microbial cells are used. Compressed microbial cells have poor shelf life and can be stored only for a short period of time. This is due to a decrease in the number of viable bacteria or a decrease in activity due to autolysis of microbial cells. If the storage conditions are not completely aseptic, bacteria and fungi easily contaminate. Therefore, it is necessary to have an operation and equipment for completely ensuring aseptic conditions. Dried microbial cells have good storage stability, but a complicated drying process is required to produce them, and a considerable amount of dead microbial cells are generated, which adversely affects the production of, for example, bread.

[0003]

The use of viable bacteria is expanding in the production of fermented products and yeast for bread making, and a simple and efficient method for preserving microbial cells is desired. An object of the present invention is to provide a method for storing microbial cells for a long period of time by a simple processing method that does not require complicated treatment steps such as drying and freezing, a microbial cell containing a microbial cell having high preservability, and the microbial cell. It is to provide a method of manufacturing a composition comprising the body. Another object of the present invention is to provide a bread dough using a microbial cell having improved storage stability, a bread obtained by baking the bread dough, and a method for producing the bread.

[0004]

The present invention relates to a composition containing a compound which reduces the water activity of microbial cells and a composition containing the microbial cells, and a compound which reduces the water activity of microbial cells to the microbial cells. The present invention relates to a method for producing a microbial cell having improved storage stability, and a method for preserving a microbial cell, which comprises mixing and preserving a compound that reduces the water activity of the microbial cell and the microbial cell.

The water activity of the microbial cells mixed with the compound is, for example, 0.2 to 0.9. Examples of the compound that reduces the water activity of microbial cells include polysaccharides. Examples of polysaccharides include starch. The microbial cells are sealed in, for example, a closed container.

The present invention also provides a dough containing a composition containing a microbial cell having an improved storage stability, which is mixed with a compound that reduces the water activity of the microbial cell, a bread obtained by baking the dough, and its production. Regarding the method.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As microbial cells, any microbial cells may be used so long as they are alive.
Microbial cells used in pharmaceuticals, cosmetics and toiletries are preferred, and microbial cells used in foods are more preferred. Examples of the microorganism include yeast, lactic acid bacterium, and acetic acid bacterium.

Examples of the yeast include yeasts belonging to the genus Saccharomyces and the genus Candida . Examples of lactic acid bacteria include genus Streptococcus, genus Leuconostoc , and pediococcu.
Lactobacillus belonging to the genus s ), the genus Lactobacillus, and the genus Bifidobacterium . Examples of acetic acid bacteria include acetic acid bacteria belonging to the genus Acetobacter .

There is no particular limitation on the method for producing microbial cells, and any method may be used. For example, microbial cells can be obtained by culturing in a medium containing a carbon source, a nitrogen source, and optionally inorganic ions. If necessary, organic trace elements such as vitamins, purine bases and pyrimidine bases can be added to the medium.

Examples of carbon sources include carbohydrates such as glucose, sucrose and maltose, molasses, vegetable oils and fats, organic acids such as acetic acid, wheat flour and rye flour, and examples of nitrogen sources include ammonia and ammonium acetate. Examples thereof include various ammonium salts such as ammonium chloride, ammonium sulfate and ammonium nitrate, dairy products such as whole milk, whole milk powder and skim milk powder, amino acids, peptone, meat extract, yeast extract, peptone, yeast extract and malt extract. Examples of inorganic ions include various phosphates, sulfates, and chlorides.

Culturing is carried out, for example, at a temperature of 10 to 50 ° C. for 1 to 10 days under aeration if necessary. The microbial cell used in the present invention is preferably a fresh microbial cell obtained by culturing, and after culturing, the microbial culture solution is collected as it is, or the microbial culture solution is harvested by means such as filtration or centrifugation. The microbial cell of the present invention is a microbial cell that has not been subjected to treatment such as drying, freezing or freeze-drying.

In utilizing microbial cells, it may be preferable to utilize useful components such as aroma substances which are produced in the medium during culturing. For example, the microbial cell is a yeast,
When used for bread making, there is a method of adding wheat flour to a medium and culturing and utilizing an aroma component generated in the culture solution. In the present invention, as the microbial cells, it is also possible to use a microbial cell culture solution as it is or a microbial cell culture solution having an increased microbial cell concentration obtained by removing a part of the culture medium after culturing, and a preserved microorganism is obtained by this method. Even when cells are used, the useful components present in the culture medium can be used.

Further, when utilizing the microbial cells, it may not be preferable to wash the microbial cells. For example, when the microbial cells are yeast, and when they are used for bread making, if the microbial cells washed with an aqueous medium such as water or a fresh medium are used and harvested, yeast odor is produced in the bread. In the present invention,
As the microbial cells, microorganisms harvested without washing with an aqueous medium can be used.

The compound which reduces the water activity of microbial cells means a compound which reduces free water existing in the outer phase of the microbial cells without being associated with the microbial cells. The water activity (denoted as Aw) is the relative humidity indicated by the ratio of the saturated vapor pressure of the composition (denoted by P) and the saturated vapor pressure of pure water (denoted by Po), and means Aw = P / Po. To do. That is, the water activity of pure water is 1.

The compound that reduces the water activity of microbial cells means a compound that reduces the water activity of the entire mixture after mixing with the microbial cells. When the microbial cells are directly used for food, the compound is preferably a compound suitable for food use. Examples of the compound that reduces the water activity of microbial cells include cellulose, polysaccharides such as starch, glucose, monosaccharides such as galactose, mannitol, sugar alcohols such as sorbitol, and the like, preferably polysaccharides, and polysaccharides. Of these, starch is particularly preferable. Examples of starch include plant starch such as potato starch, sweet potato starch, tapioca starch, wheat starch, corn starch, rice starch and the like. In addition, natural starch is hydrolyzed, heat-treated, acid-treated, alkali-treated, enzyme-treated, oxidized, acetic acid, phosphorylated, succinic acid, octenyl succinic acid, hydroxypropylated, carboxymethylated, phosphoric acid cross-linked, phosphorylated. Phosphoric acid crosslinked, acetylated phosphoric acid crosslinked,
It is also possible to use a modified starch that has been subjected to a treatment such as hydroxypropylated phosphoric acid crosslinking or acetylated adipic acid crosslinking. Furthermore, a natural starch material having a high content of plant starch and the like, a crudely purified starch derived from the natural starch material, a purified starch and the like can also be used. These compounds can be used alone or in combination of two or more. These compounds are preferably dried products.

The mixing ratio of the microbial cells and the compound that reduces the water activity of the microbial cells is not particularly limited as long as the water activity of the microbial cells can be reduced.
Further, other compounds such as fragrance substances may be mixed. The compound that reduces the water activity of microbial cells varies depending on the type of the compound, but is preferably 0.01 to 100 parts by weight, more preferably 0.1 to 10 parts by weight with respect to 1 part by weight of the microbial cells.
Parts by weight, particularly preferably 0.5 to 5 parts by weight. The water activity of the composition containing microbial cells is 0.2 to 0.
9 is preferable, 0.4 to 0.8 is more preferable, and 0.6
-0.8 is especially preferable.

The water activity can be measured by a commercially available water activity measuring device. As a concrete water activity measuring instrument, water activity measuring instrument model 5803 manufactured by Lufft can be mentioned. When the compound that reduces the water activity of microbial cells is starch, the starch content in the composition is 30 to 99% by weight.
Is preferred, 50-95% by weight is more preferred, 70-9
0% by weight is particularly preferred.

The composition of the present invention can be obtained by mixing a culture solution or microbial cells obtained by culturing with a compound that reduces the water activity of the microbial cells. The mixing method is not particularly limited, and for example, a food cutter, a mixer, a blender or the like can be used. Further, other substances such as aroma components may be mixed at the same time.

The storage condition of the composition comprising the microbial cells and the compound that reduces the water activity of the microbial cells is not particularly limited, but the storage temperature is preferably 0 to 30 ° C, and 1 to 10 ° C.
Is particularly preferable. The composition of the present invention is preferably stored in a hermetically sealed container. Examples of the closed container include glass, aluminum, resin, aluminum vapor deposition resin and the like.
Examples of the resin include polyethylene, polystyrene, polycarbonate, polypropylene, polyvinyl chloride, nylon, polyethylene terephthalate, polyvinyl alcohol, polyacrylonitrile, natural rubber, ethyl cellulose and the like. The shape of the closed container is not particularly limited, and examples thereof include a bag shape and a bottle shape.

The cell harvesting step, the composition production step and the storage step are preferably operated under aseptic conditions,
The composition of the present invention has a feature that not only the preservability of the microbial cells contained therein is high but also microorganisms other than the microbial cells are unlikely to be contaminated, so that a fermentation product is produced using the microbial cells. Thus, when strictly pure strains are not required, the above-mentioned processing steps do not have to be under completely sterile conditions. Since the microbial cell of the present invention maintains a high biological activity even after being stored for a long period of time, it can be used in the production of a fermented product or the like in the same manner as when a non-preserved microbial cell is used. The use of the composition of the present invention is not particularly limited, but a method for producing bread will be specifically described in detail.

The microbial cell of the present invention is used by adding it to bread raw materials so that the amount thereof is 0.1 to 40 parts by weight, preferably 1 to 10 parts by weight, based on 100 parts by weight of wheat flour in the bread raw material. It Examples of the bread raw material include main raw materials composed of cereal flour, yeast and salt, sugars, dairy products, eggs, oils and fats, improving agents, spices and the like, and auxiliary raw materials added as necessary.

Examples of the cereal flour include wheat flour, rye flour, rice flour, corn flour and the like, and wheat flour is preferably used. Examples of the yeast include yeast belonging to Saccharomyces cerevisiae , as long as the yeast has the ability to ferment and swell the dough.
Both are used.

Examples of sugars include sucrose, glucose, fructose,
Examples include maltose, honey, molasses, liquid sugar and candy. Examples of dairy products include whole milk, skim milk powder, whole milk powder, condensed milk and the like. Any egg may be used, but chicken eggs are usually used.

Examples of fats and oils include butter, margarine, lard, coconut oil, soybean oil, cottonseed oil, shortening and the like. Examples of the improver include yeast food, emulsifier, malt extract and the like. Examples of spices include vanilla, cinnamon, nutmeg, ginger, pepper and the like.

The dough of the present invention may be any dough used for producing bread as long as it contains the powder material of the present invention. The dough of the present invention contains the composition of the present invention in an amount of 0.1 to 4 with respect to 100 parts by weight of wheat flour in bread raw materials.
It can be produced by adding 0 parts by weight, preferably 0.5 to 10 parts by weight, to the bread raw material, optionally adding food additives and the like, and adding water and kneading. .

The bread of the present invention can be any bread prepared by baking the dough of the present invention, such as loaf of bread, confectionery bread, pastry bread, French bread, live red, croissant,
The bread may have any form such as butter roll, sweet roll, donut, steamed bun, cake, and cookie, but it is preferable that the dough of the present invention is puffed and then baked.

The method of baking the dough is 180 ° C.
150 ~
Examples include a method of frying the dough in oil and fat at about 180 ° C, a method of steaming the dough in steam at about 100 ° C, and the like. As a method of puffing the dough, a method of fermenting yeast contained in the dough is mainly used, but a method of adding a puffing agent such as baking to the dough, a layer in which the dough layers and the fat and oil layers are alternately folded and a sediment layer You may use together the method of making.

The bread making method of the present invention may be a usual bread making method such as the medium seed method, the evening seed method and the straight method, except that the dough of the present invention is used. Hereinafter, the present invention will be described with reference to examples.

Example 1 Yeast Saccharomyces cerevisia contained in Dia yeast (manufactured by Kyowa Hakko Kogyo Co., Ltd.)
e ) was isolated and cultured on a standard agar medium (Nissui Pharmaceutical Co., Ltd.).
Then, one platinum loop was inoculated into a 500 ml Erlenmeyer flask containing 300 ml of the medium having the following composition, and the mixture was shake-cultured at 28 ° C. for 48 hours.

Medium composition Glucose (manufactured by Kishida Chemical Co., Ltd.) 15% by weight Malt extract (manufactured by Kanto Chemical Co., Ltd.) 1% by weight Peptone (polypeptone, manufactured by Nissui Pharmaceutical Co., Ltd.) 1% by weight potassium dihydrogen phosphate (manufactured by Kishida Chemical Co., Ltd.) 0.1 wt% water 82.9 wt% After culturing, centrifugation was performed at 3000 G for 10 minutes to obtain a precipitate.

20% by weight of the precipitate and 80% by weight of potato starch (purified and dried sterilized horse starch, manufactured by Matsutani Chemical Industry Co., Ltd.) were mixed and dispersed to produce the microbial cell of the present invention. The water activity of the obtained microbial cells was measured using a water activity measuring device [Model 580
3, manufactured by Lufft (Germany)], it was 0.71.

50 g of the microbial cells were placed in a No. 12 polyethylene bag to remove the air phase, then sealed by heat sealing and stored at 5 ° C. After storage for the period shown in Table 1, the viable cell count was measured by the standard agar medium method. The results are shown in Table 1.

[0033]

[Table 1] As shown in Table 1, the microbial cells of the present invention are 5 ° C.
A stable viable cell count was maintained in.

Example 2 Saccharomyces cerevisi
ae ) (the same as in Example 1) was inoculated into a 500 ml Erlenmeyer flask containing 300 ml of a medium having the following composition with 1 platinum loop of the inoculum,
The culture was carried out at 28 ° C. for 48 hours with shaking.

Soft flour (Angel, manufactured by Tokyo Seimitsu Co., Ltd.) 20% by weight Potassium dihydrogen phosphate (manufactured by Kishida Chemical Co., Ltd.) 0.1% by weight Enzyme (Crystase M5K, manufactured by Daiwa Kasei Co., Ltd.) 0.02% by weight Magnesium sulfate ( Kishida Chemical Co., Ltd.) 0.02% by weight water 79.86% by weight (medium having the above composition was treated at 55 ° C. for 1 hour and then 90% by weight).
What was treated at 30 ° C. for 30 minutes was used for culture. After the culture, centrifugation was performed at 3,000 × G for 10 minutes to obtain a precipitate. 20% by weight of the precipitate and 80% by weight of potato starch (purified and dried sterilized horse starch, manufactured by Matsutani Chemical Industry Co., Ltd.) were mixed,
It was dispersed to produce the microbial cell of the present invention. A storage test was performed on the obtained microbial cells at 5 ° C., and the viable cell count was measured on a standard agar medium. The results are shown in Table 2.

[0036]

[Table 2] As shown in Table 2, the microbial cells of the present invention are 5 ° C.
A stable viable cell count was maintained in.

Example 3 Lactobacillus plantar
um ) (manufactured by Kyowa High Foods Co., Ltd.) is a medium of the following composition
1 platinum loop was inoculated into a 500 ml Erlenmeyer flask containing 1 and shake-cultured at 30 ° C. for 48 hours.

Medium composition Maltose (manufactured by Kishida Chemical Co., Ltd.) 4% by weight yeast extract (manufactured by Kanto Chemical Co., Ltd.) 1.8% by weight Peptone (polypeptone, manufactured by Nissui Pharmaceutical Co., Ltd.) 1% by weight magnesium sulfate (manufactured by Kishida Chemical Co., Ltd.) 0 0.02% by weight L-cysteine hydrochloride (manufactured by Kanto Chemical Co., Inc.) 0.03% by weight lecithin (Hosei Soybean Lecithin AY, manufactured by Hosei Essential Oil Co., Ltd.) 0.05% by weight water 93.1% by weight. By weight, potato starch (purified and sterilized horse starch, manufactured by Matsutani Chemical Industry Co., Ltd.) was mixed and dispersed at a ratio of 80% by weight to produce the microbial cell of the present invention. A storage test was performed on the obtained microbial cells at 5 ° C., and the viable cell count was measured on a standard agar medium. The results are shown in Table 3.

[0039]

[Table 3] As shown in Table 3, the microbial cells of the present invention are 5 ° C.
A stable viable cell count was maintained in.

Example 4 The microbial cells prepared in Example 2 were stored in the following evening seed raw materials for the storage period shown in Table 5, and then fermented in the following steps. After the following main kneading raw material was mixed with the fermented product, main kneading-baking was performed according to the following steps to produce bread. Table 4 shows the storage period and evaluation of bread production.

[0041]

[Table 4] When bread is made using the microbial cells preserved in the present invention, the bread does not have the peculiar smell of raw yeast, and a preferable aroma obtained by culturing in a medium containing wheat flour can be introduced.

[0042] material (Evening material) 8 parts by weight of the composition of Example 2 70 parts by weight of strong flour (Super Lilac, manufactured by Tokyo Flour Milling Co., Ltd.) East Food (Pan Diamond C-500, Kyowa Fermentation Co., Ltd.) 0.1 part by weight Salt (Nakuru four 5, manufactured by Naikai Salt Industry Co., Ltd.) 0.3 parts by weight 42 parts by weight of water (Raw material for kneading) Strong powder (Super Lilac, manufactured by Tokyo Flour Mills) 30 parts by weight Sucrose (granulated sugar ME, manufactured by Dainippon Meiji Sugar Co., Ltd.) 6 parts by weight 1.7 parts by weight of salt (Nakuru Four 5, manufactured by Naikai Salt Industry Co., Ltd.) 2 parts by weight skim milk powder (Snow Brand Milk Products Co., Ltd.) Shortening (Carrot, manufactured by Kaneka Corporation) 6 parts by weight 24 parts by weight of water

[0043] Process (Evening seed fermentation) Mixing low speed 3 minutes, medium low speed 2 minutes Forging temperature 25 ℃ Fermentation 15 hours, 28 ℃ (Main kneading-baking) Mixing low speed 3 minutes, medium low speed 2 minutes, low speed 2 minutes, medium low speed 3 minutes Forging temperature 28 ℃ First fermentation 60 minutes, 28 ℃ Split 500g Bench time 20 minutes, room temperature Molding Proofer 38 ° C, 85% RH, 1.5cm above shoulder Firing 25 minutes, 220 ° C

Example 5 To the following evening seed raw materials, the microbial cells produced in Example 3 and preserved for the storage period shown in Table 5 were added, and the evening fermentation was performed according to the following steps. After the following main kneading raw material was mixed with the fermented product, main kneading-baking was performed according to the following steps to produce bread. Table 5 shows the storage period and bread production evaluation.

[0045]

[Table 5] The preferred acid odor can be obtained by storing the product according to this method.

[0046] material (Evening material) 5 parts by weight of the composition of Example 3 Strong powder (Super Lilac, manufactured by Tokyo Flour Mills) 30 parts by weight 17 parts by weight of water (Raw material for kneading) 70 parts by weight of strong flour (Super Lilac, manufactured by Tokyo Flour Milling Co., Ltd.) Yeast (Dia yeast, Kyowa Hakko Kogyo Co., Ltd.) 3 parts by weight Sucrose (granulated sugar ME, manufactured by Dainippon Meiji Sugar Co., Ltd.) 6 parts by weight 2 parts by weight of salt (Nakuru Four 5, manufactured by Naikai Salt Industry Co., Ltd.) 2 parts by weight skim milk powder (Snow Brand Milk Products Co., Ltd.) East Food (Pan-Dia C-500, Kyowa Hakko Kogyo Co., Ltd.) 0.1 part by weight Shortening (Carrot, manufactured by Kaneka Corporation) 6 parts by weight 50 parts by weight of water

[0047] Process (Evening seed fermentation) Mixing low speed 3 minutes, medium low speed 2 minutes Forging temperature 26 ℃ Fermentation 15 hours, 28 ℃ (Main kneading-baking) Mixing low speed 3 minutes, medium low speed 2 minutes, low speed 2 minutes, medium low speed 3 minutes Forging temperature 28 ℃ Floor time 60 minutes, 28 ℃ Split 500g Bench time 20 minutes, room temperature Molding Proof Time 38 ° C, 85% RH, Shoulder 1.5cm Firing 25 minutes, 220 ° C

Example 6 To the following evening seed raw materials, microbial cells produced in Example 2 and preserved for the storage period shown in Table 6 were added, and the evening fermentation was performed according to the following steps. After mixing the following main kneading raw material with the fermented product, main kneading-baking was performed according to the following steps to produce confectionery bread. Table 6 shows the storage period and the evaluation of sweet bread production.

[0049]

[Table 6] The specific volume indicates the volume of bread (ml) / the weight of bread (g). Bread volume was determined by the rapeseed replacement method. When bread is made using the microbial cells stored in the present invention, the bread does not have the peculiar smell of raw yeast.

[0050] material (Evening material) 8 parts by weight of the composition of Example 2 Strong flour super lilac, manufactured by Tokyo Flour Milling Co., Ltd.) 70 parts by weight Salt (Nakuru four 5, manufactured by Naikai Salt Industry Co., Ltd.) 0.3 parts by weight East Food (Pan-Dia C-500, Kyowa Hakko Kogyo Co., Ltd.) 0.1 part by weight Whole egg (chicken egg) 7 parts by weight 36 parts by weight of water (Raw material for kneading) 70 parts by weight of strong flour (Super Lilac, manufactured by Tokyo Flour Milling Co., Ltd.) Sucrose (Granulated sugar ME, manufactured by Dainippon Meiji Sugar Co., Ltd.) 25 parts by weight Salt (Nakuru Four 5, manufactured by Naikai Salt Industry Co., Ltd.) 0.5 part by weight 2 parts by weight skim milk powder (Snow Brand Milk Products Co., Ltd.) 8 parts by weight of shortening (carrot, manufactured by Kaneka Corporation) Water 11 parts by weight

[0051] Process (Evening seed fermentation) Mixing low speed 3 minutes, medium low speed 2 minutes Forging temperature 25 ℃ Fermentation 15 hours, 28 ℃ (Main kneading-baking) Mixing Low speed 3 minutes, Medium low speed 2 minutes, Low speed 2 minutes, Medium low speed 2 minutes Forging temperature 28 ℃ First fermentation 60 minutes, room temperature Split 50g Bench time 20 minutes, room temperature Formation Proof time 70 minutes, 38 ° C, 85% RH                         8 minutes, 200 ° C

[0052]

EFFECTS OF THE INVENTION According to the present invention, it is possible to provide a microbial cell having a high storage stability and requiring no complicated steps such as a heat drying step and a fermented product using the same.

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) C12R 1: 865) (C12N 1/20 C12R 1:25)

Claims (21)

[Claims] 1. A composition comprising a compound that reduces the water activity of microbial cells and the microbial cells. 2. The composition according to claim 1, wherein the water activity of the composition is 0.2 to 0.9. 3. The composition according to claim 1, wherein the compound that reduces the water activity of microbial cells is a polysaccharide. 4. The composition according to claim 3, wherein the polysaccharide is starch. 5. The composition according to claim 1, wherein the microbial cell is a yeast, a lactic acid bacterium, or an acetic acid bacterium. 6. The composition according to claim 1, which is hermetically sealed in a hermetically sealed container. 7. A method for producing a microbial cell having improved preservability, which comprises mixing a compound that reduces the water activity of the microbial cell with the microbial cell. 8. The production method according to claim 7, wherein the mixing is performed so that the water activity becomes 0.2 to 0.9. 9. The method according to claim 7, wherein the compound that reduces the water activity of microbial cells is a polysaccharide. 10. The method according to claim 9, wherein the polysaccharide is starch. 11. The production method according to claim 7, wherein the microbial cell is a yeast, a lactic acid bacterium, or an acetic acid bacterium. 12. The method according to claim 7, wherein the composition cells are sealed in a closed container. 13. A method for preserving microbial cells, which comprises mixing a compound that reduces the water activity of the microbial cells with the microbial cells and storing the mixture. 14. The storage method according to claim 13, wherein the water activity is stored in a state of 0.2 to 0.9. 15. The storage method according to claim 13, wherein the compound that reduces the water activity of microbial cells is a polysaccharide. 16. The storage method according to claim 15, wherein the polysaccharide is starch. 17. The storage method according to claim 13, wherein the microbial cell is a yeast, a lactic acid bacterium, or an acetic acid bacterium. 18. The storage method according to claim 13, wherein the microbial cells are sealed in a closed container. 19. A dough containing the composition according to claim 1. 20. Bread obtained by baking the bread dough according to claim 19. 21. A method for producing bread, which uses the bread dough according to claim 19.