JP5579209B2 - Improved baker's yeast and method for producing bread using the yeast - Google Patents

Description

  The present invention relates to an improved baker's yeast used for producing high-quality breads, a method for producing breads using the yeasts, and the like.

  There are many types of bread, collectively referred to as bread, including bread, sweet bread and other bread. There are various methods for producing bread, but the most consumed bread is produced by the medium seed method or the straight rice method. In the middle seed method, the dough is first kneaded with wheat flour, water, and baker's yeast (yeast) at room temperature for about 4 hours, and then the remaining flour, water, sugar, salt, fats, etc. are added and kneaded. Is further baked after fermentation. This method is widely used in large-scale factories where automation is advanced because the finished bread is difficult to harden although the manufacturing process is complicated. On the other hand, the straight rice bran method is a method in which bread dough mixed with all ingredients at once is fermented and then baked, and is widely used in small and medium bakery due to its short working time.

  The baker's yeast used in these production methods is a species classified as Saccharomyces cerevisiae, and an important property is the ability to rapidly expand the bread dough by carbon dioxide generated in the glycolysis pathway, that is, high bread dough fermentation power .

  Since medium seed dough does not add sugar as a raw material, in medium seed dough, yeast ferments monosaccharides that are slightly present in bread dough and consumes it in about 1 hour, and the subsequent 2-3 hours are contained in the flour. Maltose produced from starch is fermented by the action of β-amylase and the like. At this time, the yeast takes maltose into cells by maltose permease and decomposes it into two glucose molecules by α-glucosidase. Moreover, in the bread dough manufactured by the straight rice bran method, yeast hydrolyzes sucrose into glucose and fructose by extracellular invertase, and ferments maltose from starch in the same manner as the medium seed dough. Therefore, as a commercially available baker's yeast, a strain having sufficient maltose permease activity, α-glucosidase activity, and high sucrose metabolic activity is used so that it can be applied to both the intermediate seed method and the straight rice bran method. Yes.

  On the other hand, in the wild yeast Saccharomyces cerevisiae isolated from the natural world, there exist strains that are found to have properties that impart a favorable flavor to bread. However, even if wild yeast has maltose fermentability, the expression of maltose metabolizing enzymes such as maltose permease and α-glucosidase is suppressed in the presence of easily metabolized sugars such as sucrose and glucose, so-called Due to catabolite repression (catabolic metabolite suppression), maltose cannot be fermented. For this reason, there is a problem that the fermenting power of wild yeast is significantly lower than that of commercially available bread yeast. Accordingly, there has been a need in the art for the development of a new wild yeast having the same high bread dough fermenting ability as commercial baker's yeast.

Heretofore, catabolite repression that simultaneously ferments both glucose and maltose from 2-deoxyglucose-resistant strains of Saccharomyces cerevisiae that can grow in a minimal medium containing maltose containing 2-deoxyglucose as the main sugar source. Canceled strains have been found (Non-Patent Documents 1 and 2). In addition, a 2-deoxyglucose resistant strain in which the fermentation power of sugar-free bread dough is increased has been isolated from cell fusion strains of wild yeast and wine yeast (Non-patent Document 3). 2-Deoxyglucose, which is a structural analog of glucose, causes catabolite repression similar to glucose but is not metabolized, and thus suppresses the expression of maltose metabolic enzymes. Therefore, it is thought that a catabolite repression release strain can be obtained by imparting 2-deoxyglucose resistance.
However, obtaining a resistant strain using a high-concentration 2-deoxyglucose-containing selective medium has a problem that other fermentation characteristics may be impaired due to strong mutation conditions. Conversely, selection at a low concentration is sufficient. There is a problem that it is difficult to obtain mutant strains.

  In addition, as a wild yeast that can produce high-quality bread by the middle seed method, there is a yeast Saccharomyces cerevisiae AK46 strain isolated from cherry cherries of Ezoyama cherry grown in Tokachi region, Hokkaido (Patent Document 1). However, since this strain also has a bread dough fermenting power lower than that of commercially available baker's yeast, it is the actual situation that a fully expanded bread cannot be obtained by the straight rice cake method.

JP 2010-68739 A

Journal of Industrial Microbiology, 6, 149-156 (1990) Applied Microbiology and Biotechnology, 42, 581-586 (1994) Improvement research of yeast for bread making "Miyano yeast", Gunma Prefectural Industrial Technology Center research report (2008)

  The present invention uses an improved mutant baker's yeast having a parent strain of a wild yeast having a high fermentability in both the middle seed method and the straight rice bran method, which is used for producing high-quality breads, and the yeast. It aims at providing the manufacturing method of breads.

  In order to achieve the above object, as a result of earnest research, the present inventors have improved wild-type yeast isolated from cherry cherries of Ezoyama cherry tree, Saccharomyces cerevisiae AK46 strain (NITE P-487), which grows naturally in Tokachi region, Hokkaido. By using mutant baker's yeast, it was found that high-quality breads can be produced by either the middle seed method or the straight rice bran method, and the present invention was completed.

That is, the embodiment of the present invention is as follows.
(1) A mutant of Saccharomyces cerevisiae AK46 strain (NITE P-487), wherein both sugar-free bread dough and sugar-added bread dough fermenting power are higher than the parent strain (and maintaining other fermentation characteristics) Improved mutant baker's yeast.
(2) The mutation is impartation of 2-deoxyglucose tolerance (particularly, impartation of 2-deoxyglucose tolerance by a selective medium containing 2-deoxyglucose at a high concentration). Improved mutant baker's yeast.
(3) Saccharomyces cerevisiae MCD4 strain (NITE P-1165), which is an improved mutant baker's yeast having 2-deoxyglucose resistance.
(4) A method for producing bread, characterized in that the improved mutant baker's yeast according to any one of (1) to (3) is used.
(5) The method for producing breads according to (4), wherein the breads are produced by a straight rice cake method.
(6) 2-deoxyglucose tolerance using a selective medium containing Saccharomyces cerevisiae AK46 strain (NITE P-487) as a parent strain and containing 0.08 to 0.10% (preferably 0.08%) of 2-deoxyglucose A method for breeding improved mutant baker's yeast, wherein both sugar-free bread dough and sugar-added bread dough fermenting power are higher than those of the parent strain, characterized in that a mutant is obtained.

  According to the present invention, improved mutant baker's yeast having a high fermentative power is provided in any bread dough of sugar-free bread and sugar-added bread, and a preferable flavor is imparted by producing bread using the yeast. It is possible to obtain high-quality breads that are sufficiently swollen (especially bread that is produced by the straight rice cake method).

It is a graph which shows medium seed | species dough fermenting power (change of the amount of carbon dioxide generated per 10 minutes) of MCD4 stock (circle mark), AK46 stock (black square mark), and HP216 stock (triangle mark). The vertical axis represents the amount of carbon dioxide generated (ml / 10 minutes), and the horizontal axis represents the fermentation time (minutes). It is a graph which shows the direct dough fermentation power (change of the amount of carbon dioxide generated per 10 minutes) of MCD4 stock (circle mark), AK46 stock (black square mark), and HP216 stock (triangle mark). The vertical axis represents the amount of carbon dioxide generated (ml / 10 minutes), and the horizontal axis represents the fermentation time (minutes).

The improved mutant baker's yeast of the present invention is obtained from a yeast Saccharomyces cerevisiae AK46 strain (NITE P-487) isolated from cherry cherries of Ezoyama cherry grown in Tokachi region, Hokkaido, as a parent strain. This AK46 strain is capable of producing breads having a preferred fruity fragrance and taste, but has a weak bread dough fermenting power (particularly, a straight dough fermenting power without addition of sugar) as compared with commercially available baker's yeast.
The improved mutant baker's yeast of the present invention is a mutant in which both the sugar-free bread dough and the sugar-added bread dough fermenting power are higher than the parent strain and maintain other fermentation characteristics (the fermentation characteristics are not impaired by the mutation). Can be obtained by stock selection method.

  A suitable method is exemplified by a method in which the AK46 strain is used as a parent strain and a 2-deoxyglucose resistant mutant is obtained using a 2-deoxyglucose-containing selective medium. The growth of yeast is inhibited by 2-deoxyglucose, but the minimum inhibitory concentration differs depending on the strain and is 0.08% for the AK46 strain. Therefore, it is preferable to use a selective medium containing 0.08 to 0.10% by weight (preferably 0.08% by weight) of 2-deoxyglucose as the selective medium. The improved mutant baker's yeast of the present invention is obtained by using such a high-concentration 2-deoxyglucose-containing selective medium, both of sugar-free bread dough and sugar-added bread dough fermenting power are higher than the parent strain, and other fermentation characteristics. It is also characterized by being a mutant strain that has also been maintained.

  In this way, several excellent mutant strains are obtained using the Saccharomyces cerevisiae AK46 strain (NITE P-487) as a parent strain, and Saccharomyces cerevisiae MCD4 strain is exemplified as one having the most suitable fermentation characteristics. The main bacteriological properties of this MCD4 strain are exemplified as follows.

(A) Bacterial morphology when cultured on YM agar medium at 25 ° C. for 3 days (1) Size of vegetative cells: 3-6 μm × 4-7 μm.
(2) Vegetative cell shape: spherical or elliptical.
(3) Type of proliferation: multipolar budding.
(4) Colony properties: light brown and shiny.
(B) Presence or absence of sporulation When cultured on an SPO medium (potassium acetate 1.0%, yeast extract 0.1%, glucose 0.05%, agar 2.0%) at 25 ° C. for 3 to 5 days, 1 to 4 Forms spherical spore.
(C) Physiological and chemical taxonomic properties (1) Range of growth: grows at 22-37 ° C.
(2) Fermentability of sugar Glucose: +
Galactose: +
Sucrose: +
Maltose: +
Lactose:-
Raffinose: +
Trehalose: +
Inulin:-
(3) Carbon source assimilation glucose: +
Galactose: +
L-sorbose:-
Sucrose: +
Maltose: +
Cellobiose:-
Trehalose: +
Lactose:-
Melibiose:-
Raffinose: +
Merezitose:-
Inulin:-
Soluble starch:-
D-xylose:-
L-arabinose:-
D-arabinose:-
D-ribose:-
L-rhamnose:-
Erythritol:-
Adonitol:-
Dulcitol:-
D-mannitol:-
D-sorbitol:-
α-methylglucoside: −
Salicin:-
Gluconic acid:-
Lactic acid:-
Succinic acid:-
Citric acid:-
Inositol:-
(4) Other assimilation and growth characteristics Potassium nitrate:-
Cadaverine:-
L-lysine:-
Ethylamine hydrochloride:-
50% glucose:-
Gelatin liquefaction:-
Degradation of arbutin:-
Decomposition of urea:-
Organic acid generation:-
Cycloheximide resistance (100 mg / l):-

  In addition, Saccharomyces cerevisiae MCD4 strain was established in 2011 (2011) in the National Institute of Technology and Evaluation, Patent Deposit Microorganisms Depositary Center (2-5-8, Kazusa Kamashi, Kisarazu City, Chiba Prefecture, Japan 292-0818). It has been deposited as NITE P-1165 on November 22.

  The obtained excellent mutant strain is preferably subcultured several times (for example, 2 to 10 times) in a medium containing 2-deoxyglucose at a concentration similar to that of the selective medium and immobilized. The improved mutant baker's yeast thus obtained can be used in various bread production methods to obtain high-quality breads with sufficient fermentative power. In particular, the baker's yeast of the present invention is characterized in that it exhibits a remarkable effect in both fermentation-free production of sugar-free breads (bread etc. produced by the straight rice process) and sugar-added breads. .

  Examples of the present invention will be described below, but the present invention is not limited to these examples, and various modifications can be made within the technical idea of the present invention.

(Acquisition of improved mutant baker's yeast)
Saccharomyces cerevisiae AK46 strain was inoculated into 10 ml of YPD liquid medium (yeast extract 1.0%, polypeptone 2.0%, glucose 2.0%) in a 200 ml Erlenmeyer flask and cultured with shaking at 150 rpm at 30 ° C. for 24 hours. . 40 ml of this culture broth was collected by centrifugation, washed twice with sterilized water, and suspended in 10 ml of sterilized water. 0.1 ml of this bacterial cell suspension was added to a minimal maltose agar medium (maltose 2.0%, Yeast Nitrogen Base without Amino Acids 0.67%) containing 0.08% 2-deoxyglucose in a petri dish (diameter 8 cm), (Agar 2.0%). After culturing two agar media at 30 ° C. for 10 days, one colony that appeared was repeatedly purified by single colony separation twice on a minimal agar medium containing 0.09% 2-deoxyglucose. It was grown on a minimal agar medium containing 10% 2-deoxyglucose and stored as MCD4 strain.

(Sugar-free bread dough fermentation power and aroma comparison confirmation test)
In order to compare the Saccharomyces cerevisiae MCD4 strain, Saccharomyces cerevisiae AK46 strain and Saccharomyces cerevisiae HP216 strain isolated from commercial baker's yeast, the sugar-free bread dough fermentation power and aroma were compared.

Each strain was cultured in 10 ml of 50 ml Erlenmeyer flask YPD medium (Bacto yeast extract 1.0%, Bacto peptone 2.0%, Glucose 2.0%) at 30 ° C. for 24 hours with shaking (150 rpm). 6 ml of YPS medium in a 300 ml baffled Erlenmeyer flask (Bacto yeast extract 2.0%, Bacto peptone 4.0%, KH ₂ PO ₄ 0.2%, MgSO ₄ .7H ₂ O 0.1%, NaCl. 0%, Adecanol LG-294 0.05%, sucrose 2.0%) was inoculated into 60 ml, and cultured with shaking at 30 ° C. for 24 hours (150 rpm). The YPS medium is a medium for enhancing the bread dough fermentation power of yeast cells described later, and sucrose and other components were sterilized separately and mixed immediately before use. The cultured cells were collected by centrifugation, washed twice with distilled water, and then placed on a dried absorbent plate for several minutes to obtain cultured cells. Although the solid content of the cultured cells is about 30%, an accurate numerical value was calculated by drying a part thereof, and in the following experiment, the weight was converted to 33% solid content.

  1.0 ml of a suspension containing 10 g of wheat flour (strong), 5.5 ml of distilled water and 0.2 g of yeast cells was kneaded for 1 minute. Prepared bread dough with no added sugar is placed in a 2.4cm x 20cm test tube, and the amount of carbon dioxide generated is introduced into a graduated cylinder in saturated saline solution, and the amount of carbon dioxide generated per hour at 30 ° C is measured as the bread dough fermenting power. As measured.

  As shown in Table 1, the sugar-free bread dough fermentation power of the MCD4 strain increased to 1.6 times that of the parent strain AK46, which was higher than that of the HP216 strain.

(Medium bread dough fermentation power comparison confirmation test)
140 g of wheat flour (strong flour), 4.0 g of cultured yeast cells of MCD4 strain, AK46 strain and HP216 strain obtained by the same method as in Example 2, 1.0 ml of ascorbic acid solution (6 mg / ml) and 83 ml of distilled water The medium dough was prepared so that the temperature when kneaded with a pin mixer at 135 rpm for 3 minutes was 30 ° C. 20 g of bread dough was divided and the change in the amount of carbon dioxide gas generated per 10 minutes was measured with a Pharmagraph II (Ato Co., Ltd. product). As a result, it was shown that the MCD4 strain generates carbon dioxide more rapidly than the AK46 strain and the HP216 strain (FIG. 1).

(Bread quality confirmation test by the middle seed method)
The bread was produced by the medium seed method, and the quality was compared. After the medium seed dough prepared in the same manner as in Example 3 was fermented at 30 ° C. for 4 hours, 60 g of flour, 10.0 g of sucrose, 4.0 g of sodium chloride, 10.0 g of shortening and 50 ml of distilled water were added thereto, and 135 rpm. And chaotic until the maximum resistance to the pin mixer. After a floor time of 30 ° C. for 20 minutes, the bread dough was divided by 100 g by hand and rounded to take a bench time of 30 ° C. for 15 minutes. This was molded with a molder and a sheeter and subjected to proof fermentation at 38 ° C. and 85% humidity for 55 minutes and then baked at 200 ° C. for 25 minutes. This was allowed to cool at room temperature, and the specific volume (ml / g) was calculated by measuring the weight and volume.

  The results are shown in Table 2. The bread made from the MCD4 strain showed a larger specific volume than the AK46 strain as in the HP216 strain. Moreover, when comparing the breads produced by the MCD4 strain and the HP216 strain, the former showed better appearance, fragrance, and taste, and showed preferable quality.

(Fermentation power comparative confirmation test of straight bread dough)
200 g of wheat flour (strong flour), 10.0 g of sucrose, 4.0 g of sodium chloride, 10 g of shortening, 4.0 g of yeast cells of MCD4 strain, AK46 strain and HP216 strain obtained by the same method as in Example 2, ascorbic acid solution 1.0 ml (20 mg / ml) and 132 ml of distilled water were mixed with a pin mixer, and a straight dough was prepared so that the temperature when kneaded was 30 ° C. 20 g of bread dough was divided and the change in the amount of carbon dioxide gas generated per 10 minutes was measured with a Pharmagraph II (Ato Co., Ltd. product). It was shown that the MCD4 strain generates carbon dioxide more rapidly than the AK46 strain, like the HP216 strain (FIG. 2).

(Bread quality confirmation test by direct method)
Bread bread was produced by the straight rice cake method and the quality was compared. The straight dough prepared in the same manner as in Example 4 was divided by 100 g by hand and rounded to take a bench time of 30 ° C. for 20 minutes. This was molded with a molder and a sheeter and subjected to proof fermentation at 38 ° C. and 85% humidity for 70 minutes, followed by baking at 200 ° C. for 25 minutes. This was allowed to cool at room temperature, and the specific volume was calculated by measuring the weight and volume.

  The results are shown in Table 3. The bread made from the MCD4 strain showed a larger specific volume than the AK46 strain as in the HP216 strain. Moreover, when comparing the breads produced by the MCD4 strain and the HP216 strain, the former showed better appearance, fragrance, and taste, and showed preferable quality.

  From these results, it can be seen that the MCD4 strain exhibits very excellent bread-making properties, and the obtained bread also has very excellent characteristics, and the quality is significantly improved as compared with conventional bread.

  The present invention is summarized as follows.

  The present invention uses an improved mutant baker's yeast having a parent strain of a wild yeast having a high fermentability in both the middle seed method and the straight rice bran method, which is used for producing high-quality breads, and the yeast. It aims at providing the manufacturing method of breads.

  And by using an improved mutant baker's yeast that is a mutant of the wild yeast Saccharomyces cerevisiae AK46 strain (NITE P-487) isolated from cherry cherries that grow naturally in the Tokachi region of Hokkaido, In any case, sufficient fermenting power is exhibited, and high-quality breads can be produced.

The accession numbers of the microorganisms deposited in the present invention are shown below.
(1) Saccharomyces cerevisiae AK46 strain (NITE P-487).
(2) Saccharomyces cerevisiae MCD4 strain (NITE P-1165).

Claims (3)

    Saccharomyces cerevisiae MCD4 strain (NITE P-1165), which is an improved mutant baker's yeast.     A method for producing bread, characterized in that the improved mutant baker's yeast according to claim 1 is used.     The method for producing breads according to claim 2, wherein the breads are produced by a straight rice cake method.

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