Yeast hydrolysate as well as preparation method and application thereof

Abstract

The invention discloses a yeast hydrolysate as well as a preparation method and application thereof. The method comprises the following steps: preparing a saccharomyces cerevisiae HKB-145051 zymophyte solution and a geotrichum candidum zymophyte solution; inoculating the saccharomyces cerevisiae HKB-145051 zymophyte liquid to a brewer's grain fermentation medium for anaerobic fermentation to obtain saccharomyces cerevisiae zymophyte milk; inoculating the saccharomyces cerevisiae fermented bacterial milk with the geotrichum candidum fermented bacterial liquid, and carrying out aerobic fermentation to obtain bacterial milk; and adding a wall breaking agent into the bacterial milk to carry out wall breaking treatment, and then drying and crushing to obtain the yeast hydrolysate. The yeast hydrolysate provided by the invention is rich in protein content, low in flavoring substance content and relatively low in production cost, can replace part of soybean meal to be applied to livestock and poultry breeding, and has important practical significance in promoting cost reduction and efficiency improvement of the livestock and poultry breeding industry.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of microorganisms and feed technology, and specifically to a yeast hydrolyzate and a preparation method and application thereof. Background Art

[0002] At present, the prices of global feed raw materials such as soybean meal, corn, and wheat continue to fluctuate greatly, especially the supply changes of soybean meal, a protein feed raw material in feed, have a great impact on the development of my country's animal husbandry. In order to ensure the sustainable development of my country's animal husbandry, the Ministry of Agriculture and Rural Affairs has issued a number of relevant policies since 2021 to promote a new model of reducing and replacing corn and soybean meal in feed. The development of new protein feed raw materials is one of the research focuses of reducing and replacing soybean meal in feed.

[0003] A large number of studies have found that microbial protein feed is a biologically active protein feed with a protein content of 20-70% and an energy of about 12-22MJ / kg. The protein content and energy level are between corn and soybean meal. Among them, yeast protein feed raw materials are the most widely developed and applied microbial protein feed resources. Brewer's yeast is one of the yeast species approved by the Ministry of Agriculture and Rural Affairs of my country for use in feed raw materials and additives. Yi Xianguo et al. (2019) found that when yeast hydrolysate was added to growing pigs at 0.05, 0.10, 0.50, and 1.00%, growth performance and feed conversion rate increased linearly. Hu Wenshuang (2018) found that adding yeast hydrolysate to the diet can significantly improve the growth performance of weaned piglets and growing and finishing pigs, enhance the body's antioxidant capacity, and improve the structure of intestinal flora. The application effect on growing and finishing pigs is better than Bacillus coagulans and antibiotics. Since yeast hydrolysates are generally rich in flavoring substances such as small peptides and nucleotides, their large-scale use in monogastric animal farming will reduce feed intake. At the same time, the product price is generally 20-25 yuan / kg, and the cost of use is too high. Therefore, the rich flavoring substances and high price are important factors limiting the large-scale use of yeast hydrolysates.

[0004] The development and use of non-corn-soybean meal type diets is one of the important technical means of “reducing costs and increasing efficiency” in fattening pig farming in my country. However, the main problem in the promotion and application of miscellaneous meal type diet raw materials is that the plant fiber content is relatively high and the breeding efficiency is lower than that of corn-soybean meal type diets. In order to cope with the application of non-corn-soybean meal type diets in fattening pig farming, the present invention provides a yeast hydrolyzate product with high protein content and low content of flavor substances and low production cost. By combining feed nutrition technical means such as precision nutrition and low-protein diets, it can replace part of soybean meal in fattening pig farming, and improve the utilization rate of feed mainly composed of miscellaneous meal protein raw materials, thereby promoting the reduction and substitution of the use of soybean meal for feed, so as to ensure the safety of feed grains in my country and ensure production efficiency. Summary of the invention

[0005] To this end, an embodiment of the present invention provides a yeast hydrolyzate and a preparation method and application thereof. The present invention uses brewer's yeast HKB-145051 and Geotrichum candidum to re-ferment, hydrolyze, break the wall, dry and crush the brewer's grains that are a by-product of beer production and processing. The obtained yeast hydrolyzate is rich in protein and low in flavor substances. At the same time, the production cost is low. It can replace part of soybean meal and be used in livestock and poultry farming, which has important practical significance for promoting cost reduction and efficiency improvement in the livestock and poultry farming industry.

[0006] In order to achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0007] According to a first aspect of an embodiment of the present invention, the present invention provides a method for preparing yeast hydrolysate, the method comprising the following steps:

[0008] (1) Preparation of fermentation broth of Saccharomyces cerevisiae HKB-145051 and Geotrichum candidum;

[0009] (2) inoculating the fermentation liquid of Saccharomyces cerevisiae HKB-145051 into the brewer's grain fermentation medium for anaerobic fermentation to obtain Saccharomyces cerevisiae fermented milk;

[0010] (3) inoculating the fermented bacterial liquid of Geotrichum candidum into the fermented bacterial milk of Saccharomyces cerevisiae for aerobic fermentation to obtain bacterial milk;

[0011] (4) adding a cell wall breaking agent to the bacterial milk for cell wall breaking treatment, and then drying and crushing to obtain the yeast hydrolyzate.

[0012] Furthermore, in step (1), the brewer's yeast HKB-145051 is subjected to slant culture activation and seed tank culture to obtain a fermentation broth of the brewer's yeast HKB-145051;

[0013] Among them, the brewer's yeast (Saccharomyces cerevisiae) HKB-145051 was deposited on June 9, 2022 at the General Microbiology Center of China Microorganism Culture Collection Administration, address: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, Postal Code 100101, Deposit Number CGMCC No.25020;

[0014] The slant culture activation step is as follows: inoculating the brewer's yeast HKB-145051 into a slant culture medium containing 130 g / L malt extract powder, 0.1 g / L chloramphenicol, and 20 g / L agar, and culturing at a constant temperature of 30° C. for 48 hours to obtain the activated brewer's yeast HKB-145051;

[0015] The seed tank culture step is as follows: inoculating the activated brewer's yeast HKB-145051 at an inoculation amount of 10-12% into a liquid culture medium containing 10% sugarcane molasses, 20 g / L peptone, 1 g / L KH2PO4, 1 g / L MgSO4·7H2O, 0.5 g / L CaCl2, 0.08 g / L chloramphenicol, and a pH value of 6.5, and culturing the culture medium at a constant temperature of 28°C and a rotation speed of 100-300 r / min for 36-40 hours in a shaking table to obtain a fermentation culture liquid of brewer's yeast HKB-145051;

[0016] The Geotrichum candidum is cultured in a seed tank to obtain a fermentation bacterial liquid of the Geotrichum candidum;

[0017] The Geotrichum candidum used in the present invention is from the Hubei Industrial Microbiological Strain Collection and Research Center, with the collection number HBCICC71016.

[0018] The seed tank culture step comprises: inoculating the candidum with an inoculum amount of 10-15% in a culture medium containing 2.0% glucose, 1.0% yeast extract, 1.0% peptone, 0.02% defoamer, and a pH value of 5.4-5.6, at a tank pressure of 0.03-0.05Mpa and an oxygen supply air volume of 3.0-6.0m 3 / h, a rotation speed of 200-500rpm, and a temperature of 26-30°C for cultivation. When the pH value rises to 6-6.4, the cultivation is completed to obtain a fermentation bacterial liquid of Geotrichum candidum.

[0019] Further, in step (2), the method for preparing the brewer's grain fermentation medium comprises: mixing wet brewer's grains with an aqueous solution containing 80 g / L starch, 20 g / L corn cob powder, 0.2% MgSO4·7H2O, 0.2% KH2PO4, and 0.1% NaCl in a volume ratio of 1:0.8-1.2, and adjusting the pH value to 5.6-5.8;

[0020] The wet brewer's grains contain 5-7% crude protein, 2-4% crude fat, 3-5% crude fiber and 80-85% moisture.

[0021] The anaerobic fermentation step is: inoculating brewer's yeast HKB-145051 fermentation liquid into brewer's grain fermentation medium at an inoculation rate of 10-15%, with an initial fermentation temperature of 28° C., an initial pH value of 6.0-6.5, and anaerobic fermentation for 48-52 hours.

[0022] Furthermore, in step (3), the aerobic fermentation step is as follows: inoculating the fermented bacterial liquid of Geotrichum candidum into the fermented bacterial milk of Saccharomyces cerevisiae at an inoculation rate of 5-8%, at a temperature of 30-32°C and a ventilation volume of 1.0-2.0 m 3 / h and ferment for 24-28h.

[0023] Furthermore, in step (4), the amount of the cell wall breaking agent added is 20-25 mg / L, and the cell wall breaking treatment conditions are: sealed treatment at 50-55°C for 4-6 hours;

[0024] The wall-breaking agent consists of zinc sulfate, beta-glucanase and mannanase in a mass ratio of 180:10:10.

[0025] According to a second aspect of the embodiments of the present invention, the present invention provides a yeast hydrolysate, which is prepared by any of the methods described above.

[0026] According to a third aspect of the embodiments of the present invention, the present invention provides the use of the yeast hydrolyzate as described above in livestock and poultry feed.

[0027] Furthermore, the yeast hydrolyzate replaces part of soybean meal in livestock and poultry feed.

[0028] Furthermore, the yeast hydrolyzate can replace 10-20 kg / t of soybean meal in livestock and poultry feed.

[0029] Furthermore, the livestock and poultry breeding feed is fattening pig feed.

[0030] The embodiments of the present invention have the following advantages:

[0031] 1. The yeast hydrolysate of the present invention is obtained by fermenting Saccharomyces cerevisiae HKB-145051 and Geotrichum candidum on brewer's grains, and is rich in three microbial proteins of Saccharomyces cerevisiae HKB-145051, Geotrichum candidum and Saccharomyces cerevisiae (brewer's grains), and has a rich protein content;

[0032] 2. The present invention optimizes the cell wall breaking conditions, and the obtained yeast hydrolyzate not only has a high protein content, but also greatly reduces the content of yeast nucleotides, small peptides and other flavoring substances, thereby avoiding the influence of low palatability caused by high yeast flavoring substance content, thereby increasing the amount that can be added to the feed;

[0033] 3. The present invention uses brewer's yeast HKB-145051 and Geotrichum candidum to jointly ferment beer production byproduct brewer's grains, and reduces the use of protease and cellulase. At the same time, no molasses is needed in the fermentation process of brewer's yeast, and the production cost is only 20-30% of the general yeast hydrolyzate, which greatly reduces the production cost of yeast hydrolyzate products and provides a technical reference for further developing microbial protein products that can replace soybean meal in large quantities;

[0034] 4. The yeast hydrolyzate of the present invention uses brewer's yeast HKB-145051 that can metabolize cellulase, which is particularly beneficial to the feeding mode of mixed meal type diets for fattening pigs, can reduce the risks of high fiber and high mycotoxin in mixed meal diets for fattening pig farming, and is helpful to promote the use of non-soybean meal protein raw materials. It has important practical significance for promoting cost reduction and efficiency improvement of my country's pig farming industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0036] Figure 1 The yeast cell wall breaking effect under different temperatures and time provided by the present invention;

[0037] Figure 2 The yeast cell wall breaking effect under different ions and concentrations provided by the present invention;

[0038] Figure 3 The yeast cell wall breaking effect under different enzymolysis conditions provided by the present invention;

[0039] Figure 4 The effect of the yeast hydrolyzate provided by the present invention replacing soybean meal on fattening pigs, wherein A is daily weight gain; B is daily feed intake; C is feed-to-weight ratio, and * indicates significant difference, P < 0.05;

[0040] Figure 5 The effect of adding yeast hydrolyzate to the barley-sorghum diet provided by the present invention on fattening pigs, wherein A is daily weight gain; B is daily feed intake; C is feed-to-weight ratio, and * indicates significant difference, P < 0.05. DETAILED DESCRIPTION

[0041] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are 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.

[0042] In the following content, the wet brewer's grains come from beer production and processing enterprises, with crude protein 5-7%, crude fat 2-4%, crude fiber 3-5%, and moisture 80-85%.

[0043] Example 1 Preparation of yeast hydrolysate

[0044] (1) Preparation of fermentation broth of Saccharomyces cerevisiae HKB-145051:

[0045] The fermentation liquid of Saccharomyces cerevisiae HKB-145051 was obtained by slant culture activation and seed tank culture.

[0046] The brewer's yeast HKB-145051 with a deposit number of CGMCC No. 25020 was inoculated into a slant medium (130 g / L malt extract powder, 0.1 g / L chloramphenicol, 20 g / L agar), and cultured at 30° C. for 48 hours to obtain activated brewer's yeast HKB-145051;

[0047] The activated Saccharomyces cerevisiae HKB-145051 was inoculated into a liquid culture medium (10% cane molasses, 20 g / L peptone, 1 g / L KH2PO4, 1 g / LMgSO4·7H2O, 0.5 g / L CaCl2, 0.08 g / L chloramphenicol, pH 6.5) with an inoculation amount of 10%. The culture was carried out in a constant temperature shaker at 28°C, a rotation speed of 200 r / min, and a culture time of 36 hours to obtain a fermentation culture liquid of Saccharomyces cerevisiae HKB-145051.

[0048] (2) Preparation of Geotrichum candidum fermentation broth:

[0049] The candidum with the deposit number HBCICC71016 was inoculated in a seed tank for cultivation, with an inoculation amount of 12%, a culture medium composed of 2.0% glucose, 1.0% yeast extract, 1.0% peptone, 0.02% defoamer (polyether polyol defoamer SGR-1810, Xingrui), and a pH value of 5.5; the culture conditions were: tank pressure of 0.03Mpa, oxygen supply air volume of 4.5m3 / h, rotation speed of 200rpm, and culture temperature of 28°C. When the pH value rose to 6.1, the cultivation was completed, and the candidum fermentation liquid was obtained.

[0050] (3) Preparation of brewer's grains fermentation medium:

[0051] After the wet brewer's grains were sterilized at 75°C for 3 minutes, an aqueous solution containing 80 g / L starch, 20 g / L corncob powder, 2 g / L MgSO4·7H2O, 2 g / L KH2PO4 and 1 g / L NaCl was added in equal volumes, mixed evenly, and the pH value was adjusted to 5.6-5.8 to obtain a brewer's grains fermentation medium.

[0052] (4) Anaerobic fermentation of Saccharomyces cerevisiae:

[0053] The brewer's yeast HKB-145051 fermentation liquid of step (1) is inoculated into the brewer's grain fermentation medium of step (3) at an inoculation rate of 10%, with an initial fermentation temperature of 28° C., an initial pH value of 6.0, and anaerobic fermentation for 52 hours to obtain brewer's yeast fermentation milk.

[0054] (5) Aerobic fermentation:

[0055] The fermented bacterial liquid of Geotrichum candidum in step (2) was inoculated into the fermented bacterial milk of Saccharomyces cerevisiae in step (4) at an inoculum rate of 5%, and the fermentation temperature was adjusted to 30°C and the ventilation volume was 1.2 m 3 / h, ferment for 24h, and obtain bacterial milk.

[0056] (6) Post-processing:

[0057] 0.10 wt % of a cell wall-breaking agent (composed of zinc sulfate, β-glucanase and mannanase in a mass ratio of 180:10:10) was added to the bacterial milk of step (5), sealed at 50° C. for 6 h, dried at low temperature, and crushed to obtain yeast hydrolyzate.

[0058] The contents of the main active ingredients in the yeast hydrolysate obtained in this example were detected and compared with commercially available yeast hydrolysate and Saccharomyces cerevisiae HKB-145051 hydrolysate. The results are shown in Table 1 below.

[0059] Table 1 Comparison of main active ingredients of yeast hydrolysate

[0060]

[0061] Note: Cellulase activity = cellulase activity + ligninase activity + xylanase activity

[0062] According to tests, the yeast hydrolyzate obtained in the embodiment of the present invention has a high protein content, is rich in active ingredients such as mannan, β-glucan and fiber degrading enzyme, and the content of flavor substances such as nucleotides is significantly lower than that of other yeast hydrolyzate products.

[0063] Example 2 Study on yeast cell wall breaking conditions

[0064] (1) Study on wall breaking temperature and time

[0065] Take an appropriate amount of the fermented yeast milk of brewer's yeast obtained in step (4) of Example 1, centrifuge it at 8000 rpm for 10 min, discard the supernatant to obtain yeast mud, and prepare yeast suspension with sterile water. Place it in a water bath at 40°C, 45°C, 50°C, 55°C, 60°C, and 65°C respectively, take a certain amount of yeast suspension every 2 hours, centrifuge it at 8000 rpm for 10 min, and measure the overflow of soluble protein in the supernatant.

[0066] The results are as follows Figure 1As shown in the figure, the optimum temperature for autolysis is above 50°C, and the soluble protein overflow reaches a peak at 4-6 hours and is relatively high. Considering the production cost, 4-6 hours at 50-55°C is selected as the best cell wall breaking time.

[0067] (2) Different Zn 2+ , Mn 2+ Effect of ion concentration on yeast cell autolysis

[0068] Take an appropriate amount of the fermented yeast milk obtained in step (4) of Example 1, centrifuge it at 8000 rpm for 10 min, and discard the supernatant to obtain yeast paste. Add 0.2, 0.5, 1.0, 2.0, 4.0, 6.0, 8.0 mg / L of Zn to the citric acid-sodium citrate buffer solution at the optimal pH, respectively. 2+ and Mn 2+ The yeast paste was resuspended and autolyzed at 55°C for 6 h, and the amount of soluble protein overflowed in the supernatant was measured.

[0069] The results are as follows Figure 2 , the zinc ion concentration is 4.0 mg / L, which is the most cost-effective concentration for treating yeast cells.

[0070] (3) Effects of adding different exogenous enzymes on yeast cell autolysis

[0071] Take an appropriate amount of the fermented yeast milk obtained in step (4) of Example 1, centrifuge it at 8000 rpm for 10 min, and discard the supernatant to obtain yeast paste. Add 4.0 mg / L of Zn 2+ After the cells were treated with 1 mg / L of different exogenous enzymes at 55°C for 4 h, the amount of soluble protein overflow in the supernatant was determined.

[0072] Table 2 Different enzyme combinations

[0073] A B C D E β-Glucanase - + + + + Mannanase - + + + + Acid protease - - + - + Fibrase - - - + +

[0074] The results are as follows Figure 3 As shown, cellulase has little effect on the yeast cell wall breaking effect. At the same time, although the wall breaking effect of adding acid protease (Group C and Group D) is the best, the purpose of the present invention is to reduce proteolysis and the production of small molecular flavor substances, so Group B (β-glucanase + mannanase) is selected as the composite enzyme.

[0075] Through experimental research, it was found that adding 20-25 mg / L of cell wall breaking agent and sealing treatment at 55-60℃ for 4-6 hours; wherein the cell wall breaking agent is a zinc ion complex enzyme, which is composed of zinc sulfate, β-glucanase, and mannanase in a mass ratio of 180:10:10, this method can obtain a more ideal yeast cell wall breaking effect.

[0076] Example 3 Application of yeast hydrolyzate in fattening pig feed

[0077] (1) Experimental study on replacing soybean meal with yeast hydrolysate in corn-soybean meal diet

[0078] This study used a corn-soybean meal based diet as the control group (CON), and replaced 5, 10, 15, and 20 kg / t of soybean meal in the diet formula with an equal amount of yeast hydrolyzate (the yeast hydrolyzate obtained in Example 1), and conducted feeding experiments on growing and finishing pigs weighing 50-75 kg.

[0079] Table 3 Basic diet design

[0080]

[0081]

[0082] Thirty boars weighing 50±5kg were selected and divided into five treatments according to Table 4, with six pigs in each treatment and each pig as a replicate. The feed intake was recorded every day, and the weight was weighed on day 60. The average daily feed intake (kg / d), average daily weight gain (g / d) and feed-to-weight ratio were calculated.

[0083] Table 4 Design without experimental group

[0084]

[0085] (2) Effect of yeast hydrolysate replacing soybean meal on growth performance of finishing pigs

[0086] See also Figure 4 The test results show that 10-15kg / t (experimental groups 2 and 3) replacing soybean meal significantly improved the growth performance (daily weight gain) and daily feed intake of fattening pigs, but the feed-to-weight ratio of 10kg / t (experimental group 2) replacing soybean meal was equivalent to the basic diet, and the feed-to-weight ratio of 15kg / t (experimental group 3) replacing soybean meal was significantly lower than the basic diet, and the feed return was higher. Therefore, considering the comprehensive factors of the price of alternative raw material soybean meal and the pig market, when the soybean meal price is at a low level, or the pig breeding market is general, 10kg / t replacing soybean meal is a better addition amount; but when the soybean meal price is high, or the pig breeding market is good, 15kg / t addition is more cost-effective.

[0087] Example 4 Application of yeast hydrolyzate in non-corn feed for fattening pigs

[0088] (1) Experimental study on replacing soybean meal with yeast hydrolysate in non-corn diets

[0089] This study used a barley-sorghum diet as the control group (CON), and conducted a feeding trial on growing and finishing pigs (50-100 kg) by replacing the soybean meal in the diet with 10 kg / t and 15 kg / t of yeast hydrolysate (the yeast hydrolysate obtained in Example 1) in equal amounts.

[0090] Table 5 Experimental diet design

[0091]

[0092] (2) Effect of yeast hydrolysate replacing soybean meal on growth performance of finishing pigs

[0093] See also Figure 5 The results showed that 10-15kg / t (experimental groups 1 and 2) replacing soybean meal significantly improved the growth performance of fattening pigs, but 15kg / t replacing soybean meal also significantly increased feed intake. Therefore, based on comprehensive consideration of feed costs and market conditions, with barley, sorghum and other energy feed raw materials, if the price of soybean meal is low, 10kg / t yeast hydrolyzate replacing soybean meal can bring better growth performance and feed return for fattening pigs; if the price of soybean meal is high and the pork market is good, you can choose to replace 15kg / t soybean meal in fattening pig feed.

[0094] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for preparing yeast hydrolysate, characterized in that: The method comprises the following steps: (1) Preparation of fermentation broth of Saccharomyces cerevisiae HKB-145051 and Geotrichum candidum; (2) inoculating the fermentation liquid of Saccharomyces cerevisiae HKB-145051 into the brewer's grain fermentation medium for anaerobic fermentation to obtain Saccharomyces cerevisiae fermented milk; (3) inoculating the fermented bacterial liquid of Geotrichum candidum into the fermented bacterial milk of Saccharomyces cerevisiae for aerobic fermentation to obtain bacterial milk; (4) adding a cell wall breaking agent to the bacterial milk for cell wall breaking treatment, and then drying and crushing to obtain the yeast hydrolyzate.

2. The method for preparing yeast hydrolyzate according to claim 1, characterized in that: In step (1), The brewer's yeast HKB-145051 was subjected to slant culture activation and seed tank culture to obtain a fermentation liquid of the brewer's yeast HKB-145051; Among them, the brewer's yeast (Saccharomyces cerevisiae) HKB-145051 was deposited on June 9, 2022 at the General Microbiology Center of China Microorganism Culture Collection Administration, address: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, Postal Code 100101, Deposit Number CGMCC No.25020; The slant culture activation step is as follows: inoculating the brewer's yeast HKB-145051 into a slant culture medium containing 130 g / L malt extract powder, 0.1 g / L chloramphenicol, and 20 g / L agar, and culturing at a constant temperature of 30° C. for 48 hours to obtain the activated brewer's yeast HKB-145051; The seed tank culture step is as follows: inoculating the activated brewer's yeast HKB-145051 at an inoculation amount of 10-12% into a liquid culture medium containing 10% sugarcane molasses, 20 g / L peptone, 1 g / L KH2PO4, 1 g / L MgSO4·7H2O, 0.5 g / L CaCl2, 0.08 g / L chloramphenicol, and a pH value of 6.5, and culturing the culture medium at a constant temperature of 28°C and a rotation speed of 100-300 r / min for 36-40 hours in a shaking table to obtain a fermentation culture liquid of brewer's yeast HKB-145051; The Geotrichum candidum is cultured in a seed tank to obtain a fermentation bacterial liquid of the Geotrichum candidum; The seed tank culture step comprises: inoculating the candidum with an inoculum amount of 10-15% in a culture medium containing 2.0% glucose, 1.0% yeast extract, 1.0% peptone, 0.02% defoamer, and a pH value of 5.4-5.6, at a tank pressure of 0.03-0.05Mpa and an oxygen supply air volume of 3.0-6.0m 3 / h, a rotation speed of 200-500rpm, and a temperature of 26-30°C for cultivation. When the pH value rises to 6-6.4, the cultivation is completed to obtain a fermentation bacterial liquid of Geotrichum candidum.

3. The method for preparing yeast hydrolyzate according to claim 1, characterized in that: In step (2), The preparation method of the brewer's grain fermentation medium comprises: mixing wet brewer's grains with an aqueous solution containing 80 g / L starch, 20 g / L corn cob powder, 0.2% MgSO4·7H2O, 0.2% KH2PO4, and 0.1% NaCl at a volume ratio of 1:0.8-1.2, and adjusting the pH value to 5.6-5.8; The wet brewer's grains contain 5-7% crude protein, 2-4% crude fat, 3-5% crude fiber, and 80-85% moisture; The anaerobic fermentation step is: inoculating brewer's yeast HKB-145051 fermentation liquid into brewer's grain fermentation medium at an inoculation rate of 10-15%, with an initial fermentation temperature of 28° C., an initial pH value of 6.0-6.5, and anaerobic fermentation for 48-52 hours.

4. The method for preparing yeast hydrolyzate according to claim 1, characterized in that: In step (3), The aerobic fermentation steps are as follows: inoculating the fermented bacterial liquid of Geotrichum candidum into the fermented bacterial milk of Saccharomyces cerevisiae at an inoculation rate of 5-8%, at a temperature of 30-32°C and a ventilation volume of 1.0-2.0 m 3 / h and ferment for 24-28h.

5. The method for preparing yeast hydrolyzate according to claim 1, characterized in that: In step (4), The amount of the wall-breaking agent added is 20-25 mg / L, and the wall-breaking treatment conditions are: sealed treatment at 50-55°C for 4-6 hours; The wall-breaking agent consists of zinc sulfate, beta-glucanase and mannanase in a mass ratio of 180:10:

10.

6. A yeast hydrolysate, characterized in that: The invention is prepared by the method according to any one of claims 1 to 5.

7. Use of the yeast hydrolyzate according to claim 6 in livestock and poultry feed.

8. The use according to claim 7, characterized in that: The yeast hydrolyzate replaces part of soybean meal in livestock and poultry feed.

9. The use according to claim 8, characterized in that: The yeast hydrolyzate replaces 10-20 kg / t of soybean meal in livestock and poultry feed.

10. The use according to claim 7, characterized in that: The livestock and poultry breeding feed is fattening pig feed.

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