JP2021078358A - Yeast and food product using the same - Google Patents

Abstract

To provide yeast having high survival rate even if freeze-thaw is repeated, and a food product using the yeast.SOLUTION: Yeast is selected which is suitable for application of food product manufacturing such as baking bread, from predetermined leaf mold on the basis of trehalose assimilation ability, assimilation ability under each type of carbon source, and fermentation ability under each type of carbon source, and furthermore, screening is performed by a freeze-thaw test, and Saccharomyces cerevisiae having excellent freeze-thaw tolerance is obtained.SELECTED DRAWING: None

Description

The present invention relates to yeast, and more particularly to yeast having high freeze-thaw resistance and foods using the same.

Examples of commercially available baker's yeast products derived from wild yeast and whose strains have been clarified include "Shirakami Kodama Yeast" (Patent Document 1, Non-Patent Document 1) and "Tokachino Yeast" (Patent Document 2). is there. "Shirakami Kodama Yeast" is a yeast isolated from humus in the temperate deciduous forest zone, and "Tokachino Yeast" is a yeast isolated from the cherry of Ezoyama cherry tree that grows naturally in the Tokachi region of Hokkaido.

Japanese Unexamined Patent Publication No. 2001-178449 Japanese Unexamined Patent Publication No. 2010-08739

J. Appl. Glycosci., Vol. 56, Suppl., 2009

Yeast used for food is generally stored or distributed in a refrigerator. Shirakami Kodama Yeast (registered trademark) is the only yeast for bread making that is stored and distributed frozen in Japan. However, when Shirakami Kodama yeast is frozen and thawed a plurality of times, the survival rate of the yeast is lowered, and it tends to be difficult to use it in fermented foods and the like. Therefore, once the frozen yeast is thawed, it is not desirable to freeze it again, and it is necessary to use it within about one week.

In view of the above circumstances, it is an object of the present invention to provide yeast having a high survival rate even after repeated freezing and thawing and a food product using the yeast.

The present inventors carried out screening using various indexes, and as a result of keen research, found a yeast capable of solving the above-mentioned problems, and completed the present invention.

[1] Saccharomyces cerevisiae having a survival rate of 70% or more after repeating the freeze-thaw treatment twice.
[2] The Saccharomyces cerevisiae according to the above [1], wherein the survival rate after repeating the freeze-thaw treatment three times is 55% or more.
[3] The trehalose content in the cells recovered after culturing in a YPD medium containing glucose as a carbon source for 2 days is 19% by weight or more based on the dry cell weight of the cells. Alternatively, the Saccharomyces cerevisiae according to any one of [2].
[4] The Saccharomyces cerevisiae according to any one of the above [1] to [3], which has salt tolerance to grow in a YPD medium containing 10% salt (w / v).
[5] Further, the Saccharomyces cerevisiae according to the above [1] to [4], which has the ability to assimilate glucose, sucrose, and maltose as carbon sources.
[6] Saccharomyces cerevisiae strains (A) or (B) below:
The identity of (A) Saccharomyces cerevisiae KAY 723 strain or (B) strain of (A) above to the entire genome sequence is 90% or more, and the survival rate after repeated freeze-thaw treatment is Strains that are 70% or more.
[7] Saccharomyces cerevisiae KAY 723 strain.
[8] A frozen yeast composition which is a frozen product containing the cells of Saccharomyces cerevisiae according to any one of the above [1] to [7].
[9] A frozen bread dough containing the cells of Saccharomyces cerevisiae according to any one of the above [1] to [7].
[10] Dried baker's yeast, which is a dried cell cell of Saccharomyces cerevisiae according to any one of the above [1] to [7].
[11] A method for producing a fermented food, which comprises fermenting using the cells of Saccharomyces cerevisiae according to any one of the above [1] to [7].
[12] A method for producing bread, which comprises baking a bread dough containing the cells of Saccharomyces cerevisiae according to any one of the above [1] to [7].
[13] A method for preserving Saccharomyces cerevisiae, wherein the cells of Saccharomyces cerevisiae according to any one of the above [1] to [7] are frozen at −10 to −30 ° C.

The present invention provides yeast with high freeze-thaw resistance. The yeast of the present invention has a high survival rate even if freeze-thaw is repeated a plurality of times, and is highly convenient for storage and distribution as a food additive or a food containing the same.

Hereinafter, embodiments of the present invention will be described. The numerical values used to specify the present invention can be specified by the method described in Examples described in detail below.

1. 1. Yeast of the Present Invention The present invention provides a yeast having high freeze-thaw resistance.
One embodiment of the present invention may be Saccharomyces cerevisiae, which has a survival rate of 70% or more after repeating the freeze-thaw treatment twice. The survival rate can be more preferably 75%, even more preferably 76, 77, 78, 79, or 80%.

In addition, another embodiment of the present invention may be Saccharomyces cerevisiae, which has a survival rate of 55% or more after repeating the freeze-thaw treatment three times. The survival rate can be more preferably 58%, even more preferably 59, or 60%.

In addition, as another embodiment of the present invention, the survival rate at the time of performing the freeze-thaw treatment once is 80% or more, more preferably 82% or more, still more preferably 83, 84, or 85% or more. Can be.

The yeast of the present invention may, as yet another embodiment, Saccharomyces cerevisiae, which highly accumulates trehalose. As for the degree of high accumulation of trehalose, for example, the content of trehalose in the cells recovered after culturing in a YPD medium containing glucose as a carbon source for 2 days is 19% by weight based on the dry cell weight of the cells. The above can be preferably 20% by weight, more preferably 23% by weight, still more preferably 25, 26, or 27% by weight.

Further, another embodiment of the present invention may be Saccharomyces cerevisiae having high salt tolerance. The presence or absence or degree of salt tolerance can be specified by, for example, applying to a YPD medium containing a predetermined concentration of salt or the like and confirming the presence or absence of proliferation. More specifically, for example, it is possible to evaluate whether or not it is possible to grow in a YPD medium containing 10% (w / v) of salt.

In yet another embodiment, the yeast of the present invention can be Saccharomyces cerevisiae, which has the ability to assimilate glucose, sucrose, and maltose as carbon sources. As described above, yeast having an assimilation ability for various sugars can be used for making various breads, and thus can be said to be excellent in bread making suitability.

A preferred embodiment of the present invention is, for example, Saccharomyces cerevisiae KAY 723 strain. The KAY 723 strain was collected with the permission of the competent authority from the buffer area of the world natural heritage "Shirakami Mountains" in Hachimori, Happo-cho, Yamamoto-gun, Akita Prefecture, as described in detail in the example section below. It is a strain isolated from the humus soil. The KAY 723 shares have been deposited as follows.
(1) (Consignment number: NITE P-03028)
(2) (Consignment date: September 26, 2019)
(3) Depositor: National Institute of Technology and Evaluation Biotechnology Center Patented Microbial Deposit Center (NPMD) (2-5-8 Kazusakamatari, Kisarazu City, Chiba Prefecture, Japan)

The KAY 723 strain exhibits the following characteristics as mycological properties. (+: Positive,-: Negative)
Freeze-thaw resistance: +
Trehalose storage capacity: +
Glucose assimilation ability: +
Sucrose assimilation ability: +
Maltose assimilation ability: +
Fermentation ability with sugar-free bread dough: +
Fermentation ability in low sucrose-containing bread dough: +
Fermentation ability in bread dough containing high sucrose: +
Good growth in the presence of glucose concentration 46% (w / v), can grow in the presence of 50% (w / v) Good growth in the presence of salt concentration 6% (w / v) 10% (w / v) ) Can grow in the presence of oval shape with nuclei and vacuoles Proliferates by budding Forming matte milky white colonies with a diameter of 2 to 8 mm on a YPD plate medium

In addition, the yeast of the present invention can be a mutant strain having high freeze-thaw resistance equivalent to that of the KAY 723 strain. For example, the mutant strain has an identity of about 90% or more with respect to the entire genome sequence of the Saccharomyces cerevisiae KAY 723 strain, and has a survival rate of 70% or more after repeating the freeze-thaw treatment twice. Can be a strain of Saccharomyces cerevisiae. In another embodiment, the mutant strain has an identity of about 90% or more with respect to the entire genome sequence of the Saccharomyces cerevisiae KAY 723 strain, and after the freeze-thaw treatment is repeated twice. Can be a strain having a survival rate of 55% or more.

Sequence identity can be determined by using known software such as BLAST (Basic Local Element Search Tool). In the yeast according to the invention, the identity of the KAY 723 strain to the entire genome sequence is preferably about 93% or more, more preferably about 95% or more, still more preferably about 96, about 97, about 98, or about 99%. That could be the end. According to the entire genome sequence of Saccharomyces cerevisiae published so far, the genome size is generally about 12 Mb to 12.5 Mb. The known sequence of Saccharomyces cerevisiae can be searched through, for example, NCBI (National Center for Biotechnology Information), DDBJ (DNA Data Bank Of Japan), and the like.

2. Utilization of yeast of the present invention The yeast of the present invention may adopt various forms. One embodiment of the present invention may be a frozen yeast composition obtained by freezing the above-mentioned Saccharomyces cerevisiae cells. As described above, the Saccharomyces cerevisiae of the present invention has excellent freeze-thaw resistance and is suitable for storage and distribution as a frozen product.

The frozen yeast composition may be, for example, frozen bread dough, frozen pizza dough, or the like. The Saccharomyces cerevisiae of the present invention, as an embodiment, has excellent bread-making suitability and is suitable as a frozen bread dough. Further, the Saccharomyces cerevisiae of the present invention, as an embodiment, has excellent salt resistance and can be suitably used for foods containing salt.

The yeast of the present invention can be added to food raw materials and used in the production of fermented foods in the same manner as ordinary yeasts. The yeast of the present invention can be suitably used in a method for producing bread.

Further, if the yeast added to the bread dough is not alive, fermentation does not proceed, and the bread dough and the swelling of the bread become insufficient. As an embodiment, the yeast of the present invention has a higher survival rate than conventional yeast even if it is repeatedly frozen and thawed in a freezer at around -18 ° C, which is widely used in household refrigerators. Therefore, bread dough for home bakery. It is suitable as such.

Further, the yeast of the present invention, as an embodiment, has an assimilation ability for glucose, sucrose, and maltose, and also has a fermentation ability for sugar-free, low-sugar, and high-sugar bread dough, and therefore has excellent bread-making suitability. There is. Therefore, the yeast of the present invention can be suitably used for bread production by adding it to bread dough and baking it.

In addition, the yeast of the present invention may be dried and in the form of dried mycelium. In the case of dried cells, they may be stored at room temperature, or may be stored refrigerated under temperature conditions of −10 ° C. or higher and lower than 0 ° C.

In addition, one embodiment of the present invention may be a method for preserving Saccharomyces cerevisiae, in which the cells of Saccharomyces cerevisiae are frozen at −10 to −30 ° C. The freezing temperature does not have to be constant. For example, after quick freezing at about −20 ° C. to −30 ° C., the product may be frozen or refrigerated at about −19 ° C. to −10 ° C. As described above, the yeast of the present invention has a higher survival rate than the conventional yeast even if it is repeatedly frozen and thawed in a freezer at around -18 ° C, which is widely used in household refrigerators. Therefore, a preferred embodiment of the yeast storage method of the present invention may be, for example, freezing storage at about −10 ° C. to −20 ° C., −15 ° C. to −19 ° C., or −18 ° C.

Hereinafter, the present invention will be specifically described with reference to examples, but the technical scope of the present invention is not limited to the following examples.

In addition, in the amount notation of the dough composition in the following Examples, Baker's Percent was used. Baker's Percentage is the weight percent based on the weight of flour used in the dough, and is abbreviated as BP. To give an example, when 70 baker's percent of water is used, 70 g of water is used for every 100 g of flour. Similarly, for 250 g of flour, 175 g of water is used.

The YPD liquid medium was prepared as follows. After accurately weighing 1 g of Yeast Extract (manufactured by Difco), 2 g of Polypepton (manufactured by Difco), and 2 g of Dextrose (manufactured by Kanto Chemical Co., Inc.), the mixture was dissolved in distilled water and scalpeled to 100 ml. This YPD liquid medium was sterilized in an autoclave at 121 ° C. for 15 minutes and cooled to room temperature before use. The YPD agar medium was used after sterilization by adding agar so as to have a concentration of 1.5% (w / v) with respect to the above-mentioned YPD liquid medium component.

Live yeast was prepared as follows. The live yeast was used as a live yeast by pre-culturing from the preserved strain and then washing the bacterial cells obtained by performing the main culture. Preserved strains of each strain are stored at -80 ° C as a 20% (w / w) glycerol suspension.
The cells were washed twice with sterile physiological saline and used as live yeast.

The KAY 723 strain, which is an example of the yeast of the present invention, was isolated by the method shown below.
1. 1. Isolation of microorganisms 1.1. Isolation of strains 0.1 g of leaf mold collected with the permission of the competent authority from the buffer area of the world natural heritage "Shirakami Mountains" in Hachimori, Hachimine-cho, Yamamoto-gun, Akita Prefecture, 200 ppm of chloramphenicol, butou Place in a medium consisting of 0.3 g of sugar, 0.1 g of peptone, 0.05 g of yeast extract, and 10 ml of tap water, and shake-culture at 25 to 26 ° C. at an amplitude of 5 cm for 5 to 7 days to measure yeast collection. After that, the cells were cultured in a koji juice agar medium having a composition of 50 g of powdered koji extract, 15 g of agar, 1,000 ml of tap water, and pH 5.0 at 27 ° C. for 3 days, and the strain was purely separated.

1.2. Selection of trehalose-producing bacteria The strain purely isolated by the above method was placed in 5 ml of YPD medium having a composition of 1 g of yeast extract, 2 g of peptone, 2 g of glucose, and 100 ml of distilled water at 30 ° C. and an amplitude of 5 cm for 2 days. Shaking culture was performed at 250 rpm to prepare a preculture. As the main culture, 1/100 amount of the preculture solution was inoculated into the YPD medium, and shaking culture was carried out at 30 ° C. and 120 rpm per minute for 2 days. The cells obtained in the main culture were centrifuged using a centrifuge at 4,000 rpm and 4 ° C. for 10 minutes, the supernatant was discarded, and the cells were collected.

0.5 g of the bacterial cells was extracted with 2.5% trichloroacetic acid, and trehalose in the extract was measured by high performance liquid chromatography (manufactured by Hitachi High-Tech Science). Eleven strains (trehalose high accumulation strains) showing a trehalose content of 19% or more based on the weight of dried cells were selected.

2. Selection of Saccharomyces cerevisiae Some yeasts are pathogenic. Among them, the yeast widely used in foods such as bread and sake is Saccharomyces cerevisiae. In order to obtain yeast that can be used for food processing such as bread making, it is necessary to select Saccharomyces cerevisiae from the trehalose high accumulation strains obtained above. Therefore, we attempted to identify and select Saccharomyces cerevisiae, which can be widely used in foods, from the 11 trehalose-rich strains obtained above.

The identification of Saccharomyces cerevisiae was performed by comparing the homology of the ribosomal RNA (rRNA) base sequence contained in the fungus. It has been shown that the rRNA base sequence has 99% or more homology of the base sequence of the ITS region between strains of the same species, and this value is generally used as a guideline for identification. Therefore, we attempted to identify by comparing the homology of the base sequences of the D1 / D2 region of the 26 / 28S rRNA gene in addition to the ITS region of the rRNA base sequence. The homology comparison of the base sequence was performed by BLAST.

As a result, 4 strains of Saccharomyces cerevisiae were obtained. Of the 4 strains, 3 strains showed 100% homology in both the ITS region and the D1 / D2 region. One strain had 99% homology in the ITS region, but the D1 / D2 region of this one strain showed 100% homology, so it was identified as Saccharomyces cerevisiae. From the above, 4 strains of yeast, Saccharomyces cerevisiae, which can be used for food, were obtained from 11 strains. These four strains are Saccharomyces cerevisiae, which highly accumulate trehalose.

3. 3. Saccharomyces cerevisiae sugar assimilation test Types of sugar-free bread include French bread and baguette. In addition to glucose, maltose is abundant as sugar contained in wheat flour. Therefore, we tried to select a strain that can grow using glucose, sucrose, or maltose as a carbon source.

Therefore, the four strains of Saccharomyces cerevisiae, which highly accumulate trehalose, obtained above were cultured with shaking in 5 ml of YPD medium at 30 ° C. and an amplitude of 5 cm for 2 days at 250 rpm to obtain a preculture solution. ..

In the YPD medium having a composition of 1 g of yeast extract, 2 g of peptone, 2 g of sugar, and 100 ml of distilled water, the type of sugar is set to either glucose 2 g, sucrose 2 g, or maltose 2 g, and three types having different sugars are used. YPD medium was prepared. A 1/100 amount of the preculture solution was placed in 5 ml of each YPD medium and suspended well, and then 200 μl of each was transplanted to a round-bottomed 96-well microplate (manufactured by Iwaki Glass Co., Ltd.). This microplate was measured for absorbance at 600 nm every hour at 30 ° C. with an incubation leader HiTS (manufactured by Sinix Co., Ltd.), and the growth of microorganisms was measured from the increase in the numerical value.

As a result, since one of the four strains grew very poorly in the presence of maltose, it was considered that there was substantially no maltose assimilation ability. As a result, three strains showing good growth even in a medium containing maltose as the sole carbon source were selected. These three strains are Saccharomyces cerevisiae, which highly accumulate trehalose and show good growth in a medium containing maltose as the sole carbon source.

4. Measurement of carbon dioxide gas generation amount in low-sugar or sugar-free bread dough For the three Saccharomyces cerevisiae strains obtained through the above "3. Saccharomyces cerevisiae sugar utilization test", the amount of carbon dioxide gas generated in each low-sugar or sugar-free bread dough. Was measured.

The amount of carbon dioxide generated was observed based on the yeast test method for bread of the Japan Yeast Industry Association. As Comparative Example 1, commercially available baker's yeast (Super Camellia Dry Yeast (Nisshin Seifun Group)) was used. As the commercially available baker's yeast, live yeast obtained by culturing in YPD medium was used.

100 g of wheat flour was accurately weighed and mixed so that water was BP = 70% and salt was BP = 1.5% to obtain a base dough. For the sugar-free dough, sucrose was not added to the base dough. For the low sugar dough, sucrose was added to the base dough at BP = 6%. Live yeast or dried yeast was added as the test yeast.

The amount of carbon dioxide generated was measured at 30 ° C. using a pharmacograph (registered trademark, manufactured by ATTO). The thermograph is a device that measures the amount of gas generated in the system over time, and the unit is ml. The amount of gas generated per unit time was measured as each gas, and the cumulative total amount of gas generated was measured as total gas. The amount of gas generated (ml) obtained was converted to 3 g as live yeast.

In the low sugar bread dough, the amount of carbon dioxide generated was measured over time for 900 minutes (15 hours). As a result of the measurement, in the low sugar bread dough, the initial carbon dioxide generation pattern was similar for all the strains. However, only one strain (No. 723 strain) of the three strains of "Saccharomyces cerevisiae" obtained through the above "3. Saccharomyces cerevisiae sugar assimilation test" and the commercially available baker's yeast of Comparative Example 1 were 6 It was found that carbon dioxide gas continued to be generated slowly over time. On the other hand, in the other two strains obtained through the above-mentioned sugar assimilation test, the generation of carbon dioxide gas decreased significantly after 6 hours, and the increase in the cumulative total amount of carbon dioxide gas generation became very gradual.
From this result, in the low sugar dough, all the strains are suitable for bread making, but No. The 723 strain and the commercially available baker's yeast of Comparative Example 1 were judged to be particularly excellent.

Similarly, as a result of measurement using sugar-free bread dough, No. A good carbon dioxide generation pattern was observed in the 723 strain and the commercially available baker's yeast of Comparative Example 1. The other two strains obtained through the above sugar assimilation test showed very similar carbon dioxide generation patterns to each other, and the amount of carbon dioxide generated in the sugar-free bread dough was No. for 0 to 10 hours. .. It was found to be considerably lower than the amount of carbon dioxide generated in 723 and Comparative Example 1.

Based on the above results, among the three strains of Saccharomyces cerevisiae obtained through the above-mentioned "3. Saccharomyces cerevisiae sugar assimilation test", the sugar-free dough was No. One of the 723 strains was determined to be the strain with the highest bread-making suitability.

Based on the results so far, Saccharomyces cerevisiae, which has excellent fermentability and highly accumulates trehalose, is No. One of the 723 strains was selected and the selection test was completed. This No. The 723 strain was named KAY 723 strain.

5. Measurement of carbon dioxide gas generation in high-sugar bread dough KAY 723, which has excellent bread-making suitability and highly accumulates trehalose, selected by the tests up to "4. Measurement of carbon dioxide gas generation in low-sugar or sugar-free bread dough" For one of the strains, the suitability for bread making in high sugar dough was examined, and the difference in fermentation characteristics from the commercially available baker's yeast of Comparative Example 1 was compared.

The high sugar dough was prepared by adding sucrose at BP = 30% to the above base dough. Other points regarding the measurement method were the same as in the case of the above-mentioned low-sugar or sugar-free bread dough.

As a result of the measurement, the amount of gas generated by the KAY 723 strain almost always exceeds the amount of carbon dioxide generated by the commercially available baker's yeast of Comparative Example 1, and the cumulative amount of gas generated always exceeds that of Comparative Example 1. The results exceeded the amount of gas generated by the commercially available baker's yeast. That is, it was judged that the KAY 723 strain had a better fermenting ability than the commercially available baker's yeast of Comparative Example 1.

From the above results, it was considered that the KAY 723 strain can be produced for any of sugar-free bread, low-sugar bread, and high-sugar bread, and it is possible to improve the time efficiency in the bread-making operation.

6. Survival rate against repeated freeze-thaw <Significance>
In order to know the resistance to freeze-thaw, the survival rate against repeated freeze-thaw was determined as follows. Generally, when the microorganism is cryopreserved, -80 ° C is used because of its high survival rate. On the other hand, the household freezer temperature of -18 ° C. is a temperature at which the survival rate of microorganisms is very low, that is, a temperature at which microorganisms are likely to die.

Therefore, yeast having a high survival rate at the household freezer temperature of -18 ° C. is highly useful for realizing repeated freeze-thaw utilization of the freezing block of live yeast used in the bakery industry.

<Measurement of survival rate>
As test bacteria, Example 1: KAY 723 strain, Comparative Example 1: Commercial baker's yeast (Super Camellia dry yeast (Nisshin Seifun Group)), Comparative Example 2: Shirakami Kodama yeast, and Comparative Example 3: Saccharomyces cerevisiae. The widely used Association No. 7 yeast was used. Live bacteria were used as each test bacterium.

As a medium, a YPD medium (yeast extract 1% (w / v), peptone 2% (w / v), glucose 2% (w / v)) was prepared. A Sakaguchi flask containing 150 mL of YPD medium was prepared, test bacteria were added, and the cells were cultured for 96 hours before the first freezing. 10 mL of the obtained culture was collected in a 15 mL centrifuge tube (3000 rpm, 10 minutes) and washed once with sterile water. Immediately after washing, the mixture was cooled with a -20 ° C freezer. It was thawed every 2 or 3 days, a part was sampled, diluted with sterile water, and applied to YPD agar medium (agar 2% (w / v)).

The number of colonies formed on the YPD agar medium was measured, and the average value of the number of colonies was calculated. The survival rate (%) was calculated from the average value of the number of colonies after each thawing and the average value of the number of initial bacteria. The results are shown in Table 1.

As shown in Table 1, Example 1 (KAY 723 strain) maintained a survival rate of 80% or more even after the first freeze-thaw and the second freeze-thaw, and after repeated freeze-thaw three times. Also showed a high survival rate of over 60%.

In contrast, the commercially available baker's yeast of Comparative Example 1 had a survival rate of about 56% after one freeze-thaw, and less than 20% after three freeze-thaw. In addition, Comparative Example 2 (Shirakami Kodama Yeast) maintained a survival rate of about 80% at the stage after the first freeze-thaw, but fell below the survival rate of 50% at the stage after the third freeze-thaw.

7. Measurement of trehalose content Table 2 shows the results of measuring the trehalose content using the above-mentioned Examples 1, Comparative Examples 1 and 2, and further, as Comparative Example 3, using Kyokai No. 7 yeast widely used as Saccharomyces cerevisiae. The measurement of the trehalose content is the same as the method described in "1.2. Selection of trehalose-producing bacteria" above.

It was revealed that the yeast of Example 1 is a yeast that highly accumulates trehalose.

8. Proliferation in the presence of high-concentration salt The YPD medium used in "1.2. Selection of trehalose-producing bacteria" above was used as the default base medium, and the salt concentration was in the range of 0 to 11%, and the predetermined salt in 1% increments was used. The growth of yeast under concentration conditions was evaluated. As the yeast, the yeasts of Example 1, Comparative Examples 1 and 2 were used. Yeast growth was measured over time using an incubation leader (manufactured by Synics) in the same manner as in "3. Saccharomyces cerevisiae sugar assimilation test" above. The measurement was performed from 0 hour to 168 hours.

In Example 1 (KAY 723 strain), the growth rate tended to be lower than that of Comparative Example 2 (Shirakami Kodama yeast) as the salt concentration increased. However, the yeast of Comparative Example 2 had a maximum salt concentration of 9%, whereas in Example 1, growth started after about 100 hours even under the condition of a salt concentration of 10%, and the maximum salt concentration was 10. It was shown that it can grow up to%. The commercially available yeast of Comparative Example 1 had a maximum salivable salt concentration of 9%. Among these three types of yeast, the yeast of Example 1 was able to grow even under the highest concentration of salt conditions, and was shown to have excellent salt tolerance.

9. Proliferation in the presence of high-concentration glucose Using the YPD medium used in "1.2. Selection of trehalose-producing bacteria" above as the default base medium, prepare YPD medium containing different concentrations of glucose, and glucose concentrations 2 to 50. Yeast growth was evaluated under predetermined glucose concentration conditions in the range up to% (w / v). As the yeast, the yeasts of Example 1, Comparative Examples 1 and 2 were used. Yeast proliferation was measured over time using an incubation leader (manufactured by Synics) in the same manner as in "3. Saccharomyces cerevisiae sugar assimilation test" above. The measurement was performed from 0 hour to 168 hours.

Example 1 (KAY 723 strain) showed good growth even at a glucose concentration of 46% (w / v), and was able to grow even at a glucose concentration of 50% (w / v). On the other hand, when the glucose concentration of the commercially available yeast of Comparative Example 1 exceeded 42% (w / v), the growth was significantly poor. Further, Comparative Example 2 (Shirakami Kodama Yeast) tended to grow inferior to Example 1 at a glucose concentration of 50% (w / v). Among Example 1, Comparative Examples 1 and 2, the yeast of Example 1 was found to have the highest sugar resistance.

Claims (13)

Saccharomyces cerevisiae having a survival rate of 70% or more after repeating the freeze-thaw treatment twice. The Saccharomyces cerevisiae according to claim 1, wherein the survival rate after repeating the freeze-thaw treatment three times is 55% or more. Either of claims 1 or 2, wherein the trehalose content in the cells recovered after culturing in a YPD medium containing glucose as a carbon source for 2 days is 19% by weight or more based on the dry cell weight of the cells. Saccharomyces cerevisiae described in item 1. The Saccharomyces cerevisiae according to any one of claims 1 to 3, which has salt tolerance to grow in a YPD medium containing 10% salt (w / v). The Saccharomyces cerevisiae according to claim 4, which has the ability to assimilate glucose, sucrose, and maltose as carbon sources. Saccharomyces cerevisiae strains (A) or (B) below:
The identity of (A) Saccharomyces cerevisiae KAY 723 strain or (B) strain of (A) above to the entire genome sequence is 90% or more, and the survival rate after repeated freeze-thaw treatment is Strains that are 70% or more. Saccharomyces cerevisiae KAY 723 strain. A frozen yeast composition which is a frozen product containing the cells of Saccharomyces cerevisiae according to any one of claims 1 to 7. A frozen bread dough containing the cells of Saccharomyces cerevisiae according to any one of claims 1 to 7. Dried baker's yeast, which is a dried cell cell of Saccharomyces cerevisiae according to any one of claims 1 to 7. A method for producing a fermented food, which comprises fermenting using the cells of Saccharomyces cerevisiae according to any one of claims 1 to 7. A method for producing bread, which comprises baking a bread dough containing the cells of Saccharomyces cerevisiae according to any one of claims 1 to 7. A method for preserving Saccharomyces cerevisiae, wherein the cells of Saccharomyces cerevisiae according to any one of claims 1 to 7 are frozen at −10 to −30 ° C.