A strain of Candida and its application

Abstract

The present invention relates to a strain of Candida and its application, belonging to the technical field of microbial fermentation. The Candida SY152 provided by the present invention is deposited in the General Microbiological Center of China Microbiological Culture Collection Administration Committee, with a deposit number of CGMCC No.31427, a deposit date of July 24, 2024, a deposit address of Beijing, China, and is classified and named as tropical Candida Candida tropicalis The Candida SY152 provided by the present invention can increase the pH value of the culture medium, and when used for fermentation of soybean paste or soy sauce, it can significantly reduce the total acid content in the soybean paste or soy sauce, while increasing the ethanol content, thereby increasing the generated alcohol and ester substances, thereby enhancing the mellow flavor of the finished soybean paste or soy sauce, and significantly improving its taste and flavor.

Description

Technical Field

[0001] The invention relates to the technical field of microbial fermentation, in particular to a strain of Candida and application thereof. Background Art

[0002] Both soybean paste and soy sauce are fermented with beans and wheat as raw materials. During the fermentation process, starch is gradually hydrolyzed to produce reducing sugars, which are used by microorganisms to mainly produce acids, alcohols and other substances. The fermentation of soybean paste and soy sauce belongs to a multi-microorganism co-fermentation system. On the basis of strict process management, natural brewing microorganisms will inevitably be introduced. The multi-strain co-fermentation process forms the rich aroma and flavor of soybean paste, but due to the uncertainty of natural inoculation, the different microbial composition and proportion in the multi-strain co-fermentation process also cause the flavor quality of the fermented semi-finished products to be unstable. For example, in the fermentation of soybean paste and soy sauce, the proliferation of acid-producing microorganisms can increase the types and contents of organic acids after fermentation and enrich the taste of the product, but their excessive reproduction will lead to high acidity after the fermentation is completed, and insufficient aroma substances such as alcohols and esters, which will have an adverse effect on the flavor of soybean paste and soy sauce.

[0003] Invention patent application CN111748481A discloses an active dry yeast for soy sauce prepared using Candida and a method for fermenting soy sauce using the same. The method uses Candida to prepare active dry yeast for soy sauce fermentation, which increases the amino acid nitrogen content and reducing sugar content, but does not study the effect of improving the sour taste and overall flavor of soy sauce.

[0004] There are also studies showing that the total acidity of soybean paste can be reduced by screening lactic acid bacteria to inhibit acid-producing Bacillus (Zhou Qiyang, Hou Jie. Screening, identification and application of a lactic acid bacterium that can improve soybean paste flavor [J]. China Brewing, 2019, 38(6)). However, in actual production, in addition to Bacillus, there are also a large number of lactic acid bacteria in the soybean paste fermentation system. This method can inhibit the acid production of Bacillus, but it cannot take into account the acid production of other types of microorganisms. Summary of the invention

[0005] The invention aims to provide a Candida sp. strain used for fermenting soybean paste and soy sauce, which can significantly reduce the total acid content in soybean paste and soy sauce and increase the ethanol content at the same time.

[0006] To achieve the above object, the present invention provides the following technical solution: a strain of Candida, which is deposited in the General Microbiological Center of China Microbiological Culture Collection Administration, with a deposit number of CGMCC No.31427, a deposit date of July 24, 2024, a deposit address of Beijing, China, and is classified and named as tropical Candida Candida tropicalis .

[0007] The invention also provides a soybean paste containing the Candida sp.

[0008] In a preferred embodiment, the inoculation amount of the Candida species in each gram of mash is 10 5 -10 7 indivual.

[0009] The invention also provides a product containing the Candida or the soybean paste.

[0010] In a preferred embodiment, the product includes microbial agents and fermentation preparations.

[0011] The present invention also provides application of the Candida, or the fermented soybean paste, or the product in preparing soybean paste and soy sauce.

[0012] The invention also provides a method for preparing a sauce product, and the Candida is inoculated during the preparation process.

[0013] In a preferred embodiment, the Candida sp. is inoculated into the mash fermented for 20 to 40 days.

[0014] In a preferred embodiment, the sauce product is soybean paste or soy sauce.

[0015] The present invention also provides a method for reducing the total acid content in a product and increasing the ethanol content at the same time, wherein the Candida is inoculated into the product raw material and fermented.

[0016] Compared with the prior art, the present invention has the following beneficial effects: the Candida sp. SY152 provided by the present invention is used for fermentation of soybean paste or soy sauce, can improve the pH of the culture medium, significantly reduce the total acid content in the soybean paste or soy sauce, and increase the ethanol content at the same time, that is, the reducing sugar in the fermentation of soybean paste or soy sauce is used more for generating ethanol instead of accumulating total acid, and after the ethanol content is increased, it can react with organic acid to generate ester substances in the fermentation maturity period, further reduce the total acid content, and increase the content of generated alcohol and ester substances, thereby enhancing the mellow flavor of the finished soybean paste or soy sauce, and significantly improving the taste and flavor of the soybean paste and soy sauce. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a diagram of a yellow-green blank culture medium in an embodiment of the present invention;

[0018] Figure 2 FIG. 1 is a diagram showing the culture of Candida SY152 in a rescreening medium according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] In the following embodiments, the koji making and fermentation of soybean paste and soy sauce are achieved by the following steps:

[0021] Bean paste

[0022] 1) Koji making process:

[0023] The pretreatment of soybeans includes: after washing the soybeans, the temperature is controlled at 98~120℃ and steamed for 8~10 minutes; the pretreatment of wheat flour includes: the temperature is controlled at 98~120℃, steamed for 20~30s, and the moisture content is controlled at 22%~24%;

[0024] The pretreated soybeans and wheat flour are mixed in a ratio of 1:10 to 1:1, inoculated with Aspergillus oryzae, and koji is made at 28 to 35°C for 38 to 45 hours to obtain brewing sauce koji.

[0025] 2) Fermentation:

[0026] The above brewed sauce koji and salt water are mixed to make sauce mash, the concentration of the salt water used is 20.5%~23.5%; the amount of salt water added is 0.9~1.5 times the weight of the brewed sauce koji. The fermentation temperature is maintained at 25~35℃, and the fermentation time is 70~100 days; after the fermentation is completed, the changes in the total acid, alcohol, reducing sugar and amino acid nitrogen content are detected, and sensory evaluation is organized.

[0027] soy sauce

[0028] 1) Koji making process:

[0029] The pretreatment of defatted soybeans includes: washing defatted soybeans, controlling the temperature at 115-120°C, controlling the pressure at 0.05-0.15MPa, and steaming for 9 minutes; the pretreatment of roasted wheat includes: controlling the temperature at 300-400°C, controlling the pressure at 0.01-0.05MPa, controlling the moisture content of roasted wheat at 0.8%, and finally crushing, and the particle size after crushing is 20-100 mesh. The pretreated defatted soybeans and roasted wheat are mixed in a ratio of 1:1.5, inoculated with Aspergillus oryzae, and then koji is made at 28-40°C for 42 hours to obtain soy sauce koji.

[0030] 2) Fermentation:

[0031] The soy sauce koji and salt water are mixed to make the sauce mash. The concentration of the salt water used is 16-20%. The koji and salt water are mixed at a weight ratio of 1:1-1:1.5. The early fermentation temperature is 8-10℃, and the fermentation time is 1-1.5 months; the middle fermentation temperature is 20-25℃, and the fermentation time is 2.5-3 months; the late fermentation temperature is 30-32℃, and the fermentation time is 1-2 months. The early, middle and late stages are sealed fermented for a total of 6 months.

[0032] In the following examples, the strain isolation and culture conditions involved are as follows:

[0033] Source of strain isolation: fermented soybean paste mash for 1-2 months.

[0034] Primary screening culture medium: PDA medium supplemented with 100 g / L NaCl.

[0035] Rescreening culture medium: Add 0.02 g / L bromocresol purple and 100 g / L NaCl to malt extract agar and adjust the pH to 5.5-5.6.

[0036] Culture conditions of Candida SY152: Streak the strain preserved in glycerol tube on PDA medium and culture it at 28~30℃ for 3~5 days.

[0037] Inoculation of Candida SY152: Inoculate the strain SY152 at 10 5 ~10 7 The inoculation amount of each / g mash is inoculated into soybean paste or soy sauce mash that has been fermented for 20 to 40 days. During the fermentation period of the mash, the environment of the mash system gradually reaches a state suitable for the rapid growth of yeast. If the inoculation time is earlier than 20 days, Candida SY152 cannot quickly adapt and reproduce in the mash, thus affecting its fermentation; if the inoculation time is later than 40 days, the reducing sugar has been excessively used by microorganisms to generate acidic substances. Even if the yeast SY152 is inoculated, the effect of reducing total acid and improving flavor cannot be achieved.

[0038] Example 1 Isolation and screening of Candida

[0039] Take 25 g of fermented soybean paste mash for 1.5 months and add it to 225 mL of sterile saline. Beat it with a homogenizer for 2 minutes to obtain 10 -1 dilution, serially dilute to obtain 10 -2 , 10 -3 , 10 -4 , 10 -5 , 10 -6100 μL of the dilution was spread on the primary screening medium containing 10% NaCl, cultured at 30°C for 5 days, single colonies with good growth were picked, and separated and purified using PDA medium containing 10% NaCl to obtain pure culture, thereby preliminarily obtaining salt-tolerant yeast.

[0040] From the purified salt-tolerant yeast strain, a single colony was picked and streaked on a rescreening medium containing 10% NaCl. After culturing at 30°C for 5 days, the strain whose medium around the colony changed from yellow-green to purple was selected, which was the strain that could increase the pH of the medium. After rescreening, strain SY152 grew fastest on the salt-containing plate, and the rescreening plate completely changed from yellow-green to purple. Figure 1 As shown, it is a yellow-green blank culture medium. Figure 2 This is the culture condition of strain SY152. The rescreening plate completely turns purple. Since the pH color change range of bromocresol purple is 5.2 (yellow) to 6.8 (purple), SY152 can turn the culture medium purple, indicating that SY152 can increase the pH of the culture medium and reduce the acidity of the culture medium.

[0041] Molecular identification: The strain SY152 was sequenced and the sequencing results were compared and analyzed in the NCBI database. The results showed that the strain SY152 was Candida tropicalis Candida tropicalis The strain was deposited in the General Microbiology Center of China Microorganism Culture Collection Administration with the deposit number CGMCC No.31427.

[0042] Example 2 Small-scale test of strain SY152 for soybean paste fermentation

[0043] The fermented soybean paste mash was taken for 30 days, and the strain SY152 was activated and cultured for 10 6 The inoculation amount of SY152 / g was inoculated into the fermented soybean paste for 30 days, and this group was used as the experimental group; the soybean paste fermented for 30 days without inoculation of strain SY152 was used as the control group; both the experimental group and the control group were controlled according to the normal soybean paste fermentation process (the fermentation temperature was maintained at 25-30°C, and the total fermentation time was 90 days). After the fermentation, the soybean paste was pasteurized to obtain the original sauce, and the changes in the total acid, alcohol, reducing sugar and amino acid nitrogen content were detected. The total acid content was detected in accordance with "GB 12456-2021 National Food Safety Standard Determination of Total Acid in Food", the alcohol content was detected in accordance with "GB 5009.225-2023 National Food Safety Standard Determination of Ethanol Concentration in Wine and Edible Alcohol", the reducing sugar content was detected in accordance with "GB 5009.7-2016 National Food Safety Standard Determination of Reducing Sugar in Food", and the amino acid nitrogen content was detected in accordance with "GB 5009.235-2016 National Food Safety Standard Determination of Amino Acid Nitrogen in Food".

[0044] The test results showed that compared with the control group, the total acid content of the experimental group was significantly reduced, indicating that strain SY152 has the effect of reducing the total acid content of fermented sauce; at the same time, the alcohol content of the experimental group was detected to be increased, while the reducing sugar content was not significantly different from that of the control group, indicating that the reducing sugar in the experimental group was used more for alcohol accumulation, while the reducing sugar in the control group was used more for total acid accumulation. It can be seen that strain SY152 has a dual effect on the regulation of fermented sauce, which can not only reduce the total acid content of fermented sauce, but also increase the alcohol content. The specific test results are shown in Table 1.

[0045] Table 1 Detection of soybean paste indexes at maturity

[0046]

[0047] Example 3 Pilot application of strain SY152 in soybean paste fermentation

[0048] After the strain SY152 was activated and cultured, 5 The inoculation amount of SY152 / g mash was inoculated into the pilot fermented soybean paste mash fermented for 20 days, and this group was used as the experimental group; the soybean paste mash fermented for 20 days without inoculation of strain SY152 was used as the control group; the experimental group and the control group were controlled according to the same soybean paste fermentation process, the temperature was controlled at 30-35°C, the pH was controlled at 4-6, and the fermentation was carried out for 3 months to obtain the soybean paste, and the total acid, alcohol, reducing sugar, and amino acid nitrogen were detected. The detection method was the same as in Example 2. The detection method of volatile flavor substances refers to the literature "Analysis of the aroma differences of 10 special soy sauces" (Shi Yige et al. [J]. Food Industry Science and Technology, 2024, 45 (04): 250-260.). After obtaining the finished product, 20 professional tasters were selected to evaluate and score the product based on ten dimensions: shape, color, aroma, sourness, sweetness, bitterness, saltiness, umami, sauce flavor and overall taste. The score range is 0-5 points. The higher the score, the better the indicator.

[0049] It can be seen from Tables 2, 3 and 4 that compared with the control group:

[0050] 1) The total acid content of the experimental group was significantly reduced, the alcohol content was significantly increased, and the reducing sugar content remained basically unchanged, indicating that strain SY152 can not only reduce the total acid content through its own metabolism, but also generate alcohol, so that the reducing sugar is used to accumulate alcohol instead of total acid.

[0051] 2) The amino acid nitrogen content in the experimental group was higher than that in the control group, indicating that strain SY152 inhibited the growth of some bacteria and reduced the consumption of amino acid nitrogen;

[0052] 3) The increase in alcohol content can increase the mellow flavor of the fermented sauce on the one hand, and on the other hand, it can react with organic acids to generate esters, which significantly improves the aroma. The alcohol content of this experimental group increased, and it can be seen from the data in Table 3 that its alcohol and ester substances are higher than those of the control group. Combined with the data in Table 4, it can be seen that the finished product fermented by the experimental group not only has a significant improvement in sourness, but also has better aroma and overall taste than the control group. Therefore, the inoculated strain SY152 can not only improve the sour taste problem in terms of taste, but also enhance the aroma of the fermented sauce, which has a significant effect on improving the overall flavor of the bean paste.

[0053] Table 2 Detection of soybean paste indexes at maturity

[0054]

[0055] Table 3 Comparison of volatile flavor compounds in mature mash

[0056]

[0057] Table 4 Sensory evaluation results of fermented sauce products

[0058]

[0059] Example 4 Pilot application of strain SY152 in soy sauce koji fermentation

[0060] After the strain SY152 was activated and cultured, 7 The inoculation amount of each / g sauce mash was inoculated into the pilot soy sauce mash fermented for 35 days, and this group was used as the experimental group; the soy sauce mash fermented for 35 days without inoculation of strain SY152 was used as the control group; the experimental group and the control group were controlled according to the same soy sauce fermentation process, the initial fermentation temperature was 8~10℃, and the fermentation time was 1.5 months; the mid-term fermentation temperature was 20~25℃, and the fermentation time was 2.5 months; the late fermentation temperature was 30~32℃, and the fermentation time was 2 months, and the early, mid-term and late stages were closed for a total of 6 months. After the fermentation was completed, it was squeezed to obtain the soy sauce crude oil, and its total acid, alcohol, reducing sugar, amino acid nitrogen and volatile flavor substances were detected, and the detection method was the same as in Example 3. After obtaining the finished product, 20 professional tasters were selected to evaluate and score from ten dimensions of body shape, color, aroma, sourness, sweetness, bitterness, saltiness, umami, sauce flavor and comprehensive taste, where the score was 0-5 points, and the higher the score, the better the indicator.

[0061] It can be seen from Tables 5, 6 and 7 that compared with the control group:

[0062] 1) The total acid content of the experimental group was significantly reduced, the alcohol content was significantly increased, and the reducing sugar content remained basically unchanged, indicating that strain SY152 can not only reduce the total acid content through its own metabolism, but also generate alcohol, so that the reducing sugar is used to accumulate alcohol instead of total acid.

[0063] 2) The amino acid nitrogen content in the experimental group was higher than that in the control group, indicating that strain SY152 inhibited the growth of some bacteria and reduced the consumption of amino acid nitrogen;

[0064] 3) The increase in alcohol content can increase the mellow flavor of soy sauce on the one hand, and on the other hand, it can react with organic acids to generate ester substances, increase the ester flavor, and significantly improve the aroma. The alcohol content of this experimental group increased, and it can be seen from the data in Table 6 that its alcohol substances and ester substances are higher than those of the control group. Combined with the data in Table 7, it can be seen that the finished soy sauce fermented in the experimental group is not only significantly improved in sourness, but also has better aroma and comprehensive taste than the control group. Therefore, the inoculated strain SY152 can not only improve the sour taste problem in terms of taste, but also enhance the aroma of soy sauce, which has a significant effect on the overall flavor of soy sauce.

[0065] Table 5 Detection of soy sauce crude oil index

[0066]

[0067] Table 6 Comparison of volatile flavor compounds in crude soy sauce oil

[0068]

[0069] Table 7 Sensory evaluation results of finished soy sauce

[0070]

[0071] From the above embodiments, it can be seen that the Candida SY152 provided by the present invention is used for fermentation of soybean paste or soy sauce, which can increase the pH of the culture medium, significantly reduce the total acid content in soybean paste or soy sauce, and increase the ethanol content. It can react with organic acids to generate ester substances during the fermentation maturity period, further reduce the total acid content, and increase the content of alcohol and ester substances, thereby enhancing the mellow flavor of the finished soybean paste or soy sauce, and improving its aroma and overall taste.

[0072] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, which are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A strain of Candida, characterized in that: The Candida species is deposited in the General Microbiology Center of the China Microorganism Culture Collection Administration, with a deposit number of CGMCC No. 31427, a deposit date of July 24, 2024, a deposit address of Beijing, China, and a classification name of Candida tropicalis.

2. A moromi containing the Candida sp. according to claim 1.

3. The mash according to claim 2, characterized in that: In each gram of mash, the inoculation amount of the Candida species is 10 5 -10 7 indivual.

4. A microbial agent or fermentation preparation containing the Candida according to claim 1 or the mash according to claim 2.

5. Use of the Candida albicans according to claim 1, or the fermented soybean paste according to claim 2, or the microbial agent or fermented preparation according to claim 4 in the preparation of soybean paste or soy sauce.

6. A method for preparing a sauce product, characterized in that: In the preparation process, the Candida yeast of claim 1 is inoculated into the sauce mash fermented for 20 to 40 days, and the sauce product is soybean paste or soy sauce.

7. A method for reducing the total acid content in a product and increasing the ethanol content, characterized in that: The Candida yeast of claim 1 is inoculated into soybean paste fermented for 20 to 40 days and fermented, and the product is soybean paste or soy sauce.

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