Yarrowia lipolytica Z6-2 as well as fungicide and application thereof

Abstract

The invention provides Yarrowia lipolytica Z6-2 as well as a microbial inoculum and application of the Yarrowia lipolytica Z6-2, and belongs to the technical field of food fermentation. The preservation number of the Yarrowia lipolytica Z6-2 is CGMCC (China General Microbiological Culture Collection Center) No.31548, the preservation unit of the Yarrowia lipolytica Z6-2 is CGMCC (China General Microbiological Culture Collection Center), and the preservation date of the Yarrowia lipolytica Z6-2 is August 5, 2024. The Yarrowia lipolytica Z6-2 disclosed by the invention is high in tolerance, has obvious advantages in the production of ester compounds, and has obvious potential in the aspect of improving the flavor of a fermented product; and the product can be symbiotic with lactic acid bacteria, so that the quality, flavor and functional components of fermented food can be further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of food fermentation, and in particular relates to Yarrowia lipolytica Z6-2 and a bacterial agent and application thereof. Background Art

[0002] The natural fermentation environment contains rich microbial resources, among which lactic acid bacteria and yeast often coexist. In some cases, specific yeasts and lactic acid bacteria can ferment synergistically in a suitable environment, promote each other, and have a positive impact on the flavor of fermented products. For example, studies have shown that there is a complementary mechanism between the metabolites of lactic acid bacteria and yeasts. Yeasts can provide nutritional factors for lactic acid bacteria, and lactic acid bacteria can provide energy sources for yeasts.

[0003] However, the accumulation of lactic acid is a common problem in the production of fermented foods. Excessive lactic acid can cause the food to taste too sour, affecting the quality and flavor of the product. Therefore, how to effectively reduce the lactic acid content has become one of the research focuses in the field of food fermentation.

[0004] Although there are some methods for dealing with lactic acid problems in the fermentation process, there are still many limitations. Traditional physical or chemical methods may damage the natural characteristics of the product or introduce unnecessary chemical residues. Among biological methods, the comprehensive effect of existing microbial strains in reducing lactic acid content and improving flavor still needs to be improved. For example, some strains may only work under limited conditions, have poor adaptability to the environment, or fail to effectively produce rich flavor substances while reducing lactic acid.

[0005] Therefore, it is of great significance to find a microbial strain with strong tolerance, which can effectively reduce the lactic acid content and significantly improve the flavor of fermented products. This will not only help solve practical problems in the fermented food industry, but also meet consumers' demand for high-quality and uniquely flavored fermented foods, and promote the further development of food fermentation technology. Summary of the invention

[0006] In view of this, the object of the present invention is to provide a Yarrowia lipolytica Z6-2, which has strong tolerance, obvious advantages in the production of ester compounds, significant potential in improving the flavor of fermented products, and can coexist with lactic acid bacteria.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] A Yarrowia lipolytica Z6-2, with a preservation number of CGMCC No.31548.

[0009] The present invention also provides a bacterial agent containing the Yarrowia lipolytica Z6-2.

[0010] Preferably, the viable count of Yarrowia lipolytica Z6-2 is ≥ 1×10 7 CFU / mL.

[0011] The present invention also provides a method for preparing the bacterial agent, wherein the Yarrowia lipolytica Z6-2 bacterial suspension is inoculated into a YDP liquid culture medium for culture. Preferably, the pH value of the YDP liquid culture medium is 3-6, the inoculation amount is 5%-15%, and the culture temperature is 25-35°C.

[0012] The present invention also provides a bacterial agent containing the Yarrowia lipolytica Z6-2 and lactic acid bacteria, wherein the lactic acid bacteria include one or more of Leuconostoc citrinum, Lactobacillus breve or Lactobacillus plantarum.

[0013] The present invention also provides a method for preparing the bacterial agent, wherein the Yarrowia lipolytica Z6-2 bacterial suspension and the lactic acid bacteria suspension are inoculated into a symbiotic culture medium for symbiotic culture at 30-35° C. Preferably, the symbiotic culture medium has a formula of: 1L of 15-20° BX saccharified malt juice, 5g / L yeast extract, 10g / L peptone, and lactic acid to adjust the pH to 3.5-4.0.

[0014] The present invention also provides the use of the Yarrowia lipolytica Z6-2 or bacterial agent in the preparation of fermented food. Preferably, the Yarrowia lipolytica Z6-2 has the ability to produce esters, enriching the flavor of the fermented food.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The present invention provides a Yarrowia lipolytica Z6-2, which has strong tolerance (low temperature resistance, acid resistance, salt resistance, and ethanol resistance) and can be applied to a variety of fermentation environments; it also has a strong ability to produce esters and aromas, which can effectively improve the aroma and flavor of fermented products. In addition, it has a relatively balanced performance on volatile compounds such as aldehydes, ketones, and acids, which helps to form a complex flavor combination, can bring a richer and unique flavor to fermented foods, and meet consumers' demand for flavor diversification. Yarrowia lipolytica Z6-2 can also coexist with a variety of lactic acid bacteria, which helps to improve fermentation efficiency and product quality, and enhance the flavor and functional components of fermented foods. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The colony morphology and microscopic examination photos of Yarrowia lipolytica Z6-2;

[0018] Figure 2 is the phylogenetic tree of Yarrowia lipolytica Z6-2;

[0019] Figure 3is the growth curve of Yarrowia lipolytica Z6-2;

[0020] Figure 4 is the total ester content of the fermentation broth of different strains;

[0021] Figure 5 is the content of volatile flavor compounds in the fermentation broth of different strains.

[0022] Biological Deposit Description

[0023] The Yarrowia lipolytica Z6-2 of the present invention is classified and named as Yarrowia lipolytica (Yarrowialipolytica), the preservation unit is the General Microbiology Center (CGMCC) of the China Microbiological Culture Collection Administration, the preservation unit address is the Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, the preservation number is CGMCC.No:31548, and the preservation date is August 5, 2024. DETAILED DESCRIPTION

[0024] The present invention provides a Yarrowia lipolytica Z6-2, the deposit number of which is CGMCC.NO:31548. The bacterium is derived from the naturally fermented soybean paste flora. 60 The strain was obtained by Co-γ-ray irradiation. In the soybean paste fermentation environment, the bacterial competition is fierce. The strain can exist in such an environment, indicating that it has strong adaptability, which provides the possibility for its application in various fermentation industrial scenarios.

[0025] The present invention also provides a bacterial agent containing the Yarrowia lipolytica Z6-2, preferably the number of viable bacteria of the Yarrowia lipolytica Z6-2 is ≥ 1×10 7 CFU / mL

[0026] The present invention also provides a method for preparing the bacterial agent, wherein the Yarrowia lipolytica Z6-2 bacterial suspension is inoculated into a YDP liquid culture medium for culture. As an implementation method, the YDP liquid culture medium of the present invention has a formula of: 10 g / L yeast extract, 20 g / L peptone, and 20 g / L glucose.

[0027] In the present invention, the pH value of the YDP liquid culture medium is preferably 3-6, and the pH value is more preferably 4; the inoculation amount of the Yarrowia lipolytica Z6-2 bacterial suspension is preferably 5%-15%, and more preferably 10% (v / v); the culture temperature is preferably 25-35°C, and more preferably 29°C.

[0028] The present invention also provides a bacterial agent containing the Yarrowia lipolytica Z6-2 and lactic acid bacteria, wherein the lactic acid bacteria include one or more of Leuconostoc citrinum, Lactobacillus brevis or Lactobacillus plantarum. The Yarrowia lipolytica Z6-2 of the present invention can be symbiotically cultured with Leuconostoc citrinum, and the two have a synergistic effect; and can also be symbiotically cultured with Lactobacillus brevis and Lactobacillus plantarum, and the growth of the two does not affect each other.

[0029] The present invention also provides a method for preparing the bacterial agent, which comprises inoculating a Yarrowia lipolytica Z6-2 bacterial suspension and a lactic acid bacteria suspension into a symbiotic culture medium for symbiotic culture at 30-35°C.

[0030] In the present invention, the preferred culture temperature is 32°C; the preferred symbiotic culture medium formula is: 1L of 15-20°BX saccharified malt juice, 5g / L yeast extract, 10g / L peptone, and lactic acid to adjust the pH to 3.5-4.0.

[0031] The present invention also provides the use of Yarrowia lipolytica Z6-2 or its bacterial agent in the preparation of fermented food. Preferably, Yarrowia lipolytica Z6-2 has the ability to produce esters, which enriches the flavor of the fermented food.

[0032] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0033] Example 1

[0034] Screening of strain Z6-2

[0035] (1) Bacterial source

[0036] Naturally fermented soybean paste from the Northeast region, packaged in 50g bags.

[0037] (2) Irradiation mutagenesis of bacterial strains

[0038] Irradiation treatment was carried out at the Irradiation Center of Liaoning Academy of Agricultural Sciences. 60 The Co-γ ray static irradiation method was used, and the irradiation dose was set to 0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6 kGy. The irradiation needed to be flipped 360° once during the process to ensure uniform dose.

[0039] (3) Preparation of bacterial solution

[0040] The irradiated soybean paste was diluted with sterile water of equal mass ratio, centrifuged at 800-1000 r / min, the supernatant was removed, and the precipitate was repeatedly washed 3-5 times with 10 mL of sterile water to obtain the bacterial solution.

[0041] (4) Screening of irradiated dominant bacterial flora

[0042] The obtained bacterial liquid was mixed with an equal volume of modified YPD culture medium (containing 8-10 mL / L lactic acid), and cultured at 28°C for 3-5 days to obtain fermentation liquid. The number of viable bacteria and lactic acid content of the fermentation liquid after treatment with different irradiation doses were compared, and their lethality was calculated. It was determined that the soybean paste bacterial liquid induced by 0.6 kGy irradiation was the dominant bacterial community.

[0043] (5) Isolation and screening of single bacteria

[0044] Dilute the 0.6 kGy irradiated soybean paste solution to 10 -4 , 10 -5 , 10 -6 Gradient, 0.1 mL of each dilution was spread on YPD agar medium plates, and inverted for 48 h at 28 °C. Strains with different morphology, size and color were selected, and streaked three times in succession according to the three-zone streak method. Then, the strains were transferred to YPD culture medium (containing 8-10 mL / L lactic acid), and incubated at 28 °C for 24 h. The yeast with the highest number of viable bacteria was screened out and named Z6-2.

[0045] Example 2

[0046] Morphological and biological identification of strain Z6-2

[0047] Streak strain Z6-2 on YDP agar medium and culture at 28℃ for 2 days. Observe the colony morphology. The colonies are regular round, milky white, opaque, moist, and smooth without wrinkles. Figure 1 As shown on the left; microscopic examination revealed that the bacteria are round in shape, colorless and transparent single cells, such as Figure 1 Shown right.

[0048] The strain was sent to Shanghai Paisono Biotechnology Co., Ltd. for 16s rDNA identification. The results showed that strain Z6-2 was Yarrowia lipolytica. The basic local alignment search tool (BLAST) module in NCBI was used to draw the phylogenetic tree of the screened strains with the help of MEGA7.0 software. The results are shown in Figure 2 .

[0049] The growth curve of Yarrowia lipolytica Z6-2 was determined by turbidimetry. 600 (Optical density at 600nm) The results are as follows Figure 3 As shown, it can be seen that Yarrowia lipolytica Z6-2 began to enter the logarithmic growth phase after 4 hours and entered the stable phase after 16 hours, and the number of microorganisms reached the maximum value and remained relatively stable.

[0050] Example 3

[0051] Tolerance verification of Yarrowia lipolytica Z6-2

[0052] (1) Low temperature resistance

[0053] The bacterial suspension was prepared with distilled water and inoculated into YDP liquid medium at a ratio of 1:9. The viable bacteria were cultured at 21°C, 25°C, 29°C, 33°C, and 35°C for 24 h. Three purchased strains of Yarrowia lipolytica were used as controls, with the preservation numbers of CGMCC No.31032, CCTCC No.M 2023974, and CCTCC No.M 2022320, respectively.

[0054] Table 1 The number of viable bacteria of each strain at different temperatures

[0055]

[0056] The viable bacterial counts (CFU / mL) of different strains at 21°C, 25°C, 29°C, 33°C and 37°C are shown in Table 1. The viable bacterial count of Z6-2 at 21°C was 2.39×10 7 CFU / mL, which is significantly higher than the viable count of other strains at the same temperature. The viable count of CGMCC No.31032 at 21°C is only 0.42×10 7 CFU / mL. The viable bacterial counts of CCTCC No.M 2023974 and CCTCC No.M 2022320 at 21°C were 1.56×10 7 CFU / mL and 1.66×10 7 CFU / mL. The viable count of Z6-2 was high in the range of 21°C to 35°C, and reached a peak value (6.44×10 7 CFU / mL), indicating that it can grow well in a wide temperature range. The viable counts of other strains decreased significantly at lower temperatures, showing poor low-temperature resistance. Z6-2 maintains a higher metabolic activity at lower temperatures, has a more stable cell membrane structure, and can maintain normal physiological functions at low temperatures. In summary, the Z6-2 strain exhibits good low-temperature resistance and can maintain a higher viable count in a wider temperature range.

[0057] (2) pH resistance

[0058] The bacterial suspension was prepared with distilled water and inoculated into YDP liquid medium at a ratio of 1:9. The pH value was adjusted to 2, 3, 4, 5, and 6 with lactic acid. The culture was shaken at 29°C for 24 hours, and the number of viable bacteria was determined. Three purchased strains of Yarrowia lipolytica were used as controls, with the preservation numbers of CGMCC No.31032, CCTCC No.M 2023974, and CCTCC No.M 2022320, respectively.

[0059] Table 2 The number of viable bacteria of each strain at different pH

[0060]

[0061]

[0062] As shown in Table 2, when the pH is less than 4, the number of viable bacteria of the strain increases with the increase of pH value. When the pH is 4, the number of viable bacteria of Z6-2 is 53.81×10 6 CFU / mL, which is also significantly higher than other strains, indicating that it has a stronger adaptability in acidic environments. When the pH exceeds 4, the trends of the strains are different. The live bacterial counts of Z6-2 and CGMCC No.31032 first increase and then decrease, the live bacterial counts of CCTCC No.M 2023974 continue to increase, and the live bacterial counts of CCTCC No.M2022320 first decrease and then increase. When the pH is 5, the live bacterial count of Z6-2 is 47.18×10 6 CFU / mL, although slightly lower than pH 4, is still significantly higher than other strains, indicating that it can maintain high activity even in a near-neutral environment. In summary, the Z6-2 strain has a high number of viable bacteria in the pH range of 2-5, has good acid resistance, and adapts to a wider pH range, which gives it advantages in certain specific application scenarios.

[0063] (3) Salt tolerance

[0064] The bacterial suspension was prepared with distilled water and inoculated into YDP liquid medium at a ratio of 1:9, containing 2%, 4%, 6%, 8%, and 10% salt by volume, and cultured at 30°C in a shaking incubator for 24 hours to determine the number of viable bacteria. Three purchased strains of Yarrowia lipolytica were used as controls, with the preservation numbers being CGMCC No.31032, CCTCC No.M 2023974, and CCTCC No.M 2022320, respectively.

[0065] Table 3 The number of viable bacteria of each strain at different salt concentrations

[0066]

[0067] As shown in Table 3, compared with other strains, the Z6-2 strain can still maintain a higher viable count at higher salt concentrations (such as 8% and 10%). For example, at a salt concentration of 10%, the viable count of Z6-2 was 3.46×10 6CFU / mL, while the viable counts of other strains were lower than this value. From low salt concentration to high salt concentration, the Z6-2 strain can survive well, showing its good adaptability to environmental changes. In a high-salt environment, the difference in osmotic pressure inside and outside the cell increases. The Z6-2 strain may regulate the osmotic pressure by accumulating specific organic solutes (such as glycerol, proline, etc.), thereby protecting the cells from damage. In summary, the advantages of the Z6-2 strain in a high-salt environment are mainly reflected in its high salt tolerance and wide adaptability, which may be due to the combined effect of its special genetic characteristics, osmotic pressure regulation mechanism, enzyme activity and other factors.

[0068] (4) Ethanol resistance

[0069] The bacterial suspension was prepared with distilled water and inoculated into YDP liquid medium at a ratio of 1:9, containing 4%, 8%, 12%, 16%, and 20% anhydrous ethanol, respectively, and cultured at 30°C in a shaking incubator for 24 hours to determine the number of viable bacteria. Three purchased strains of Yarrowia lipolytica were used as controls, with the preservation numbers of CGMCC No.31032, CCTCC No.M 2023974, and CCTCC No.M 2022320, respectively.

[0070] Table 4 The number of viable bacteria of each strain at different ethanol concentrations

[0071]

[0072] As shown in Table 4, the number of viable bacteria of CGMCC No.31032 dropped sharply to 10×10 6 Below, the number of live bacteria in CCTCC No.M 2023974 dropped sharply when the ethanol concentration was 8%, and the number of live bacteria in CCTCC No.M2022320 gradually and evenly decreased with the increase of ethanol concentration. When the ethanol concentration reached 20%, the number of live bacteria in Z6-2 was 1.08×10 6 , other strains could hardly grow. The number of viable bacteria of Z6-2 strain at different ethanol concentrations was higher than that of other control groups, showing stronger tolerance and adaptability. This may be because Z6-2 strain has a better metabolic regulation mechanism or a more efficient stress response system, which enables it to maintain high activity in a high concentration ethanol environment.

[0073] Example 4

[0074] Verification of the esterification capacity of Yarrowia lipolytica Z6-2

[0075] (1) The germinated barley is ground into powder, 4-5 times the volume of water is added and mixed evenly, boiled at 50-70°C for 30-60 minutes, filtered to prepare saccharified wort (sugar content 15-20°Bx), cooled, added with 8-10 mL / L lactic acid, sterilized, and prepared into an ester production medium.

[0076] (2) The activated Yarrowia lipolytica Z6-2 was repeatedly rinsed with distilled water and then cultured in a shaking incubator at 30°C until the number of viable cells reached 10 6 CFU / mL order, and prepare bacterial liquid for later use.

[0077] (3) The bacterial solution was inoculated into the ester-producing medium at a volume ratio of 10%, and cultured at 30°C for 4 days. The uninoculated medium was used as a blank control, and the purchased Yarrowia lipolytica was used as a comparison. The preservation numbers were CGMCC No. 31032, CCTCC No. M 2023974, and CCTCC No. M 2022320, respectively.

[0078] (4) Take 100 mL of fermentation broth and 50 mL of ultrapure water for atmospheric distillation, collect a certain amount of distillate, and determine the total ester content by titration. The calculation formula is as follows:

[0079]

[0080] In the formula: C1 is the concentration of NaOH standard titration solution, mol / L; C2 is the concentration of HCl standard titration solution, mol / L; V1 is the volume of NaOH standard titration solution added during saponification, mL; V2 is the volume of HCl standard titration solution consumed in back titration, mL; V3 is the distillate sampling volume, mL; 0.08812 is the mass of ethyl acetate equivalent to 1.00mL NaOH standard titration solution, g.

[0081] Total esters are an important indicator of the ability of yeast to produce esters and aroma. The results of ester production performance of different yeasts are as follows: Figure 4 As shown, under the same fermentation conditions, the Z6-2 strain can produce the highest total ester content, reaching 3.84 g / L. By comparing with known strains, it can be clearly seen that the Z6-2 strain has a significant advantage in total ester content, which makes it a very potential choice.

[0082] (5) Prepare Yarrowia lipolytica Z6-2 bacterial solution (the number of viable cells reaches 10 7 CFU / mL) was inoculated into the ester-producing medium at a volume ratio of 10%, and cultured at 30°C and 150 r / min for 5 days, with the uninoculated medium as a blank control. After fermentation, the supernatant was obtained by centrifugation at 8000 r / min for 10 minutes.

[0083] (6) Add 10 mL of supernatant, 4 g of NaCl, and 10 μL of internal standard solution (2-octanol, mass concentration of 164 μg / L) to the headspace bottle, equilibrate at 55 °C for 15 min, extract for 40 min, and then perform automatic injection. Desorb the sample in the injection port at 230 °C for 5 min.

[0084] (7) The volatile flavor substances in the ester-producing medium after fermentation were determined by GC-MS. Qualitative analysis was performed based on the measured mass spectrum and the 11-spectral library search of the National Institute of Standards and Technology of the United States combined with the retention index. The internal standard method was used for semi-quantitative analysis, and the content of the analyte was calculated using the peak area ratio of the analyte to the internal standard.

[0085] like Figure 5 As shown in the figure, the Z6-2 strain has a significant advantage in the production of ester compounds, and its ester content is about 26.38 mg / L, which is much higher than other strains. Ester compounds are important aroma components in many foods and beverages, so the Z6-2 strain has significant potential in improving product flavor. The Z6-2 strain also has a relatively high content of alcohol compounds, second only to esters. Alcohol compounds also make an important contribution to flavor, which further enhances the flavor advantage of the Z6-2 strain. Although the content of other volatile compounds such as aldehydes, ketones and acids is not as prominent as esters and alcohols, the performance of the Z6-2 strain on these compounds is still relatively balanced, which helps to form a complex flavor combination. In summary, the Z6-2 strain shows significant advantages in the production of volatile flavor compounds, especially in the production of ester compounds, which makes it have high potential and value in multiple application fields.

[0086] Example 5

[0087] Symbiotic relationship between Yarrowia lipolytica Z6-2 and different lactic acid bacteria

[0088] (1) Yarrowia lipolytica Z6-2 and lactic acid bacteria were activated in PDY and MRS culture, respectively, and repeatedly washed with sterile water to prepare bacterial suspensions. The suspensions were cultured in a shaking incubator at 30°C and 37°C for 24 h, respectively, and centrifuged at 800 rpm. The supernatant was removed and the precipitate was retained for later use.

[0089] (2) The lactic acid bacteria used in the symbiotic experiment included Leuconostoc citraceus (BNCC 194779), Lactobacillus casei (BNCC134415), Lactobacillus helveticus (BNCC 189793), Lactobacillus breve (CGMCC No.31284), and Lactobacillus plantarum (CGMCC No.31547), which were independently bred and registered with the China Center for Microbiological Collection.

[0090] (3) Yeast extract (0.5 g / 100 mL) and peptone (1 g / 100 mL) were added to saccharified wort (sugar content 15-20° Bx), and the pH was adjusted to 3.5-4.0 with lactic acid to prepare a symbiotic culture medium.

[0091] (4) The Yarrowia lipolytica Z6-2 obtained in step (1) was inoculated into a symbiotic culture medium with different lactic acid bacteria in equal proportions, and cultured in a shaking incubator at 32° C. for 24 h.

[0092] (5) After the culture was completed, the OD of the mixed fermentation broth of each symbiotic bacteria was measured and compared. 600 The value is the OD value of the fermentation broth mixed in equal proportion after its single culture. 600 The values ​​were used as the control to determine the most suitable lactic acid bacteria for the symbiotic culture of Yarrowia lipolytica Z6-2.

[0093] Table 5 Growth of Z6-2 and lactic acid bacteria when cultured alone or together

[0094]

[0095] Note: D: OD600nm value of 2mL lactic acid bacteria and 2mL yeast cultured separately; H: OD600nm value of 1mL yeast and 1mL lactic acid bacteria mixed; G: OD600nm value of 1mL mixed fermentation broth and 1mL uninoculated culture medium mixed.

[0096] As shown in Table 5, Z6-2 and Leuconostoc citrinum showed a synergistic effect when co-fermented or mixed again, and the number of both microorganisms increased. This relationship may be due to the complementary metabolites between the two, or because they create a microenvironment that is conducive to the growth of each other. There is an antagonistic effect between Z6-2 and Lactobacillus casei and Lactobacillus helveticus, which means that when these two bacteria coexist with Z6-2, their growth may be inhibited, resulting in a decrease in the number of colonies. This may be due to resource competition, the production of harmful metabolites, or direct antimicrobial activity. Z6-2 can coexist well with Lactobacillus breve and Lactobacillus plantarum, indicating that they can coexist harmoniously without significantly affecting their respective growth. This relationship suggests that these microorganisms may not need the same resources, or they have evolved a mechanism to share resources without hindering each other. These interactions are important for the quality, flavor, and production of functional components of fermented foods.

[0097] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A Yarrowia lipolytica Z6-2, characterized in that The deposit number of the Yarrowia lipolytica Z6-2 is CGMCC No.31548.

2. A bacterial agent containing the Yarrowia lipolytica Z6-2 according to claim 1.

3. The bacterial agent according to claim 2, characterized in that The viable count of Yarrowia lipolytica Z6-2 is ≥1×10 7 CFU / mL.

4. The method for preparing the bacterial agent according to claim 2 or 3, characterized in that: The Yarrowia lipolytica Z6-2 bacterial suspension was inoculated into YDP liquid medium for culture.

5. The preparation method according to claim 5, characterized in that: The pH value of the YDP liquid culture medium is 3-6, the inoculation amount is 5%-15%, and the culture temperature is 25-35°C.

6. The bacterial agent according to claim 2 or 3, characterized in that: The invention also contains lactic acid bacteria, which include one or more of Leuconostoc citraceus, Lactobacillus brevis or Lactobacillus plantarum.

7. The method for preparing the bacterial agent according to claim 6, characterized in that: The Yarrowia lipolytica Z6-2 bacterial suspension and the lactic acid bacteria suspension were inoculated into the symbiotic culture medium for symbiotic culture at 30-35°C.

8. The preparation method according to claim 7, characterized in that: The symbiotic culture medium formula is: 1L of 15-20° BX saccharified malt juice, 5g / L yeast extract, 10g / L peptone, and lactic acid to adjust the pH to 3.5-4.

0.

9. Use of the Yarrowia lipolytica Z6-2 according to claim 1, the bacterial agent according to any one of claims 2 or 3, or the bacterial agent according to claim 6 in the preparation of fermented food.

10. The use according to claim 9, characterized in that: The Yarrowia lipolytica Z6-2 has the ability to produce esters, thus enriching the flavor of the fermented food.

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