Yeast culture with high protein content as well as preparation method and application thereof

Abstract

The invention discloses a high-protein-content yeast culture as well as a preparation method and application thereof, and belongs to the technical field of biology. The invention discloses a preparation method of a yeast culture, which comprises the following steps: mixing DDGS (distillers dried grains with soluble) and corn protein powder, adding an enzyme preparation 1, saccharomycetes and auxiliary materials for primary fermentation, and finally adding bacillus subtilis, bacillus coagulans, glucose and an enzyme preparation 2 for secondary fermentation to obtain the yeast culture. According to the invention, corn source alcohol-soluble protein is hydrolyzed to generate soluble polypeptide, small peptide and amino acid which are easy to digest and absorb through the enzymolysis effect of protease; through fermentation of beneficial microorganisms, various organic acids and thallus metabolites are generated, the taste of the feed is improved, and the probiotic effect is improved. According to the high-protein yeast culture, the problems of digestibility, palatability and the like of original corn byproducts serving as feed raw materials are solved, and value-added modification of the corn byproducts is achieved.

Description

Technical Field

[0001] The invention relates to the field of biotechnology, in particular to a yeast culture with high protein content and a preparation method and application thereof. Background Art

[0002] Corn is one of the most important food crops in the world, and it is widely used in many fields such as food, feed and industry. In the process of corn processing, a large number of by-products are produced, mainly including corn protein meal and DDGS. These by-products are rich in nutrients, but due to their complex structure and the presence of anti-nutritional factors, they have problems such as low digestibility and poor palatability when used directly as feed, which limits their application in the feed industry. At present, although some studies have tried to improve the quality of corn processing by-products through enzymatic hydrolysis or microbial fermentation, most methods have the following problems: Limited enzymatic hydrolysis effect: The effect of a single enzyme preparation is limited, and it is difficult to fully degrade complex polysaccharides and proteins. Low fermentation efficiency: Traditional fermentation methods often take a long time, and the protein content in the product is not significantly increased. High cost: The existing modification methods are expensive and are not conducive to large-scale industrial production.

[0003] Yeast culture is a probiotic product composed of a series of metabolic activities of probiotic yeast acting in a specific matrix under certain fermentation conditions. It contains a substrate with changed properties, a small amount of active yeast and a large amount of bacterial metabolites. With the rapid development of animal husbandry, the demand for high-quality feed raw materials is growing. Yeast culture, as a feed additive with high nutritional value, is widely used in the feed breeding industry. Traditional yeast-derived products mainly adopt liquid fermentation. Although liquid fermentation has the advantages of easy control of fermentation conditions and fast fermentation speed, it also has some shortcomings. For example, the product after liquid fermentation has a high water content and requires complex drying treatment, which not only increases the production cost, but also may cause the loss of some nutrients. In addition, the equipment investment for liquid fermentation is large, the production environment requirements are high, and it is not conducive to large-scale production. Solid-state fermentation refers to the fermentation process carried out by microorganisms on a solid matrix under the condition of no or almost no free water. The equipment for solid-state fermentation is simple, the investment is small, the operation is convenient, and it is suitable for large-scale production. However, the current solid-state fermentation method still has problems such as low conversion efficiency and difficult to accurately control fermentation conditions in production.

[0004] Therefore, it is of great significance to provide an efficient and low-cost method to prepare a yeast culture with high protein content by fermenting corn gluten meal and DDGS, thereby significantly improving its digestibility and palatability and realizing the value-added modification of corn by-products. Summary of the invention

[0005] The purpose of the present invention is to provide a high-protein yeast culture and a preparation method and application thereof to solve the problems existing in the above-mentioned prior art. The high-protein yeast culture prepared by the present invention can be used as a high-quality feed raw material and is widely used in high-end aquatic products, laying poultry and various young animals.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] Technical solution 1: A method for preparing a yeast culture with a high protein content, comprising the following steps: firstly mixing DDGS and corn gluten powder, then adding enzyme preparation 1, yeast and auxiliary materials for the first fermentation, and finally adding Bacillus subtilis, Bacillus coagulans, glucose and enzyme preparation 2 for the second fermentation to obtain the yeast culture.

[0008] DDGS refers to dried distiller's grains containing soluble solids. In the process of fermenting corn to produce ethanol, the starch is converted into ethanol and carbon dioxide, and other nutrients such as protein, fat, fiber, etc. are left in the distiller's grains.

[0009] Preferably, DDGS can be wet DDGS separated from corn alcohol industry without drying, and corn gluten meal can be wet corn gluten meal separated from corn starch industry without drying.

[0010] Furthermore, in terms of mass ratio, the ratio of the DDGS to the corn gluten meal is 1:1-2 (dry matrix).

[0011] Preferably, the first fermentation is to adjust the initial pH of the material to 4.0-4.5, maintain the moisture of the material at 45-55% during the solid-state aerobic fermentation stage, maintain the material temperature at 30-40°C during the fermentation process, and the fermentation time is 40-48 hours.

[0012] Preferably, the second fermentation is carried out by raising the temperature to 50°C, allowing the yeast cells to autolyze for 18-24 hours, and the autolysis rate reaches more than 60%.

[0013] Preferably, the yeast culture product with a protein content greater than 50% is obtained by low temperature drying. Preferably, fluidized bed low temperature drying is used, and the material temperature is kept below 60°C during the drying process.

[0014] Furthermore, the enzyme preparation 1 comprises saccharifying enzyme, neutral protease, acid protease, Aspergillus niger culture, hemicellulase and acid cellulase.

[0015] Furthermore, the added amount of saccharifying enzyme is 200-500U / g, the added amount of neutral protease is 500-1000U / g, the added amount of acid protease is 300-600U / g, the added amount of Aspergillus niger culture is 0.5-1%, the added amount of hemicellulase is 100-200U / g and the added amount of acid cellulase is 20-50U / g.

[0016] Furthermore, the auxiliary materials include urea and calcium carbonate; the added amount of urea is 0.5-2%, and the added amount of calcium carbonate is 3-5%.

[0017] Furthermore, the amount of yeast added is 0.5-1×10 8 (pieces / g).

[0018] Furthermore, the inoculation amounts of the Bacillus subtilis and the Bacillus coagulans are 0.1-0.5×10 8 (pcs / g) and 0.5-1×10 8 The amount of glucose added is 0.5-2%, and the enzyme preparation 2 includes acid protease, neutral protease, mannanase and nuclease.

[0019] Furthermore, the added amount of the acidic protease is 100-500 U / g, the added amount of the neutral protease is 300-500 U / g, the added amount of the mannanase is 100-300 U / g, and the added amount of the nuclease is 5-10 U / g.

[0020] Technical Solution 2: The yeast culture prepared by the preparation method.

[0021] Technical solution three: Application of the yeast culture in improving feed efficiency.

[0022] Technical Solution 4: Application of the yeast culture in improving animal production performance.

[0023] The present invention produces a variety of organic acids and bacterial metabolites through yeast fermentation, which can improve the taste of feed and enhance the probiotic effect. It is also rich in a variety of digestive enzymes, can balance the microbial community, promote intestinal function, and improve feed efficiency and animal production performance.

[0024] The present invention discloses the following technical effects:

[0025] In order to increase the protein content in common yeast culture and improve the utilization value of corn gluten powder and DDGS, the present invention proposes a method for preparing a yeast culture with high protein content. The present invention mixes DDGS and corn gluten powder in proportion to form a fermentation raw material, adds enzyme preparations, yeast and various auxiliary materials, and then performs solid-state ventilation aerobic fermentation to make the yeast count greater than 3×109 / g (microscopic count), then add composite bacteria, glucose and enzyme preparations for solid anaerobic fermentation to make the bacteria autolyze, and finally dry at low temperature to obtain a yeast culture with crude protein>50%, acid-soluble protein content>20%, bacteria autolysis rate>60%, and mannan>1.5%. On the one hand, the present invention hydrolyzes corn-derived alcohol-soluble protein to generate soluble polypeptides, small peptides and amino acids that are easy to digest and absorb through the enzymatic action of protease; on the other hand, through fermentation by beneficial microorganisms, a variety of organic acids and bacterial metabolites are produced, which improves the taste of feed and enhances the probiotic effect. The high-protein yeast culture of the present invention is a high-quality protein feed raw material, which is widely used in high-end aquatic products, ruminants, economic animals and various young animals, and can improve animal production performance.

[0026] The present invention uses traditional corn processing byproducts - corn protein powder and DDGS as raw materials, adds a variety of enzyme preparations and brewer's yeast, and performs pure solid-state aerobic fermentation, so that the number of yeast in the product reaches more than 3 billion / g, improving the digestibility and palatability of the original corn byproducts as feed raw materials, and realizing the value-added modification of corn byproducts. Through yeast fermentation, a variety of organic acids and bacterial metabolites are produced, which can improve the taste of feed and enhance the probiotic effect. It is also rich in a variety of digestive enzymes, can balance the microbial community, promote intestinal function, and improve feed efficiency, animal production performance and food safety. The high-protein yeast culture processed by this method can be used as a high-quality feed raw material and is widely used in high-end aquatic products, laying poultry and various young animals. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 The figure is a flow chart of the preparation of the yeast culture of the present invention. DETAILED DESCRIPTION

[0029] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0030] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0031] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0032] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0033] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0034] In order to increase the protein content in ordinary yeast culture and improve the utilization value of corn gluten meal (water content 40-60%) and DDGS (65-70%), the present invention proposes a method for preparing a yeast culture with high protein content. The preparation flow chart is shown in Figure 1 .

[0035] Corn gluten meal and DDGS were purchased from Zhucheng Haotian Pharmaceutical Co., Ltd. and Guotou Hailun Bioenergy Co., Ltd., respectively; Aspergillus niger culture was purchased from Shandong Hezhong Kangyuan Biotechnology Co., Ltd.; saccharifying enzyme, hemicellulase, acid cellulase, acid protease, neutral protease, mannanase and nuclease were purchased from Shandong Longkote Enzyme Preparation Co., Ltd. and Xiasheng Biotechnology Development Co., Ltd.; Bacillus subtilis, Bacillus coagulans and yeast were purchased from Wuhan Xinhuayang Co., Ltd.; urea was purchased from Shandong Hualu Hengsheng Group Co., Ltd.; glucose was purchased from Shandong Xiwang Sugar Co., Ltd.

[0036] Example 1 Fermentation of high-protein yeast culture using dry raw materials as substrate

[0037] 1. Materials

[0038] Corn gluten meal (dry, 10.2% moisture content), DDGS (dry, 11.5% moisture content).

[0039] 2. Processing method

[0040] 2.1 Premix corn gluten meal and DDGS. Take 1.5kg corn gluten meal, 1.5kg DDGS and 1.3kg water and mix well in a mixer.

[0041] 2.2 Aerobic fermentation

[0042] Add 200 U / g of saccharifying enzyme, composite protease (500 U / g of neutral protease, 300 U / g of acid protease), 100 U / g of hemicellulase, 20 U / g of acid cellulase, 1% urea, and 0.5% of Aspergillus niger culture to the premix and mix well. Inoculate 1×10 yeast 8 (pieces / g), and add 3% calcium carbonate to adjust the pH to 4.2. After mixing the materials, spread them on the tray with a layer thickness of 6 cm and cover them with wet gauze. Place the tray in a 35℃ constant temperature incubator for 48 hours, turn the materials and add water every 12 hours to keep them moist, and keep the moisture content of the materials at 55%.

[0043] 2.3 Anaerobic fermentation

[0044] 2% glucose was added to the above aerobic fermented materials, and enzyme preparations were added at a ratio of 100U / g acid protease, 300U / g neutral protease, 100U / g mannanase, and 5U / g nuclease, and 0.1×10 8 (pcs / g) and 1×10 8 (individuals / g) of Bacillus subtilis and Bacillus coagulans were inoculated, mixed and put into a sealed bag, and placed in a 50°C incubator for 24 hours.

[0045] 2.4 Low temperature drying

[0046] The fermented product was placed in a 60°C forced air drying oven and dried until the moisture content was less than 10%.

[0047] 3. Detection indicators

[0048] The two raw materials and the dried yeast culture samples after fermentation were taken to determine the contents of crude protein, acid-soluble protein and mannan, and the DDGS raw material and the samples after aerobic fermentation were taken to count the number of yeast using a hemocytometer.

[0049] 4. Results and Analysis

[0050] The nutritional indexes of yeast culture prepared with dry raw materials as substrate are shown in Table 1.

[0051] Table 1 Nutrient composition index of yeast culture and raw materials

[0052]

[0053] As shown in Table 1, after fermentation and enzymatic hydrolysis of dry corn gluten meal and dry DDGS, the crude protein content was 51.03%, and the acid-soluble protein content reached 26.32%, which was much higher than the acid-soluble protein content in corn gluten meal and DDGS raw materials. The acid-soluble protein accounted for more than 50% of the crude protein, indicating that most of the corn gluten was modified and hydrolyzed into small peptides with high digestibility. The yeast count after aerobic fermentation reached 3.28×10 9 / g, indicating that yeast grew well on the substrate, and the mannan content reached 1.88% after fermentation.

[0054] Example 2 Preparation of high-protein yeast culture using wet raw materials as substrate

[0055] 1. Materials

[0056] Corn gluten meal (45% moisture content), DDGS (65% moisture content).

[0057] 2. Processing method

[0058] 2.1 Pre-mix corn gluten meal and DDGS. Take 2kg corn gluten meal and 1kg DDGS and mix them in a mixer.

[0059] 2.2 Aerobic fermentation

[0060] After the premix is ​​mixed, 500 U / g of saccharifying enzyme, composite protease (neutral protease 1000 U / g, acid protease 600 U / g), hemicellulase 200 U / g, acid cellulase 50 U / g, 2% urea, 5% calcium carbonate and 0.5% Aspergillus niger culture are added, and 0.5×10 yeast is inoculated. 8 (pieces / g), mix the materials evenly and spread them on the tray with a layer thickness of 6cm, and cover with wet gauze. Place the tray in a 40℃ constant temperature incubator for fermentation for 40h, turn the materials and add water every 12h to keep the materials moist, and keep the moisture content of the materials at 45%.

[0061] 2.3 Anaerobic fermentation

[0062] 0.5% glucose was added to the above aerobic fermented material, and enzyme preparations were added at a ratio of 500U / g acid protease, 500U / g neutral protease, 300U / g mannanase, and 10U / g nuclease, and 0.5×10 8 (pcs / g) and 1×10 8 The mixture was inoculated with Bacillus subtilis and Bacillus coagulans in an amount of 100 μg / g, mixed and put into a sealed bag, and placed in an incubator at 50°C for 18 h.

[0063] 2.4 Low temperature drying

[0064] The fermented product was placed in a 60°C forced air drying oven and dried until the moisture content was less than 10%.

[0065] 2.5 Detection indicators

[0066] The two raw materials and the dried yeast culture samples after fermentation were taken to determine the contents of crude protein, acid-soluble protein and mannan, and the DDGS raw material and the samples after aerobic fermentation were taken to count the number of yeast using a hemocytometer.

[0067] 2.6 Results and Analysis

[0068] The nutritional indexes of yeast culture prepared with wet raw materials as substrate are shown in Table 2.

[0069] Table 2 Nutrient composition index of yeast culture and raw materials

[0070]

[0071] As shown in Table 2, after the wet corn gluten meal and wet DDGS were fermented and hydrolyzed to prepare yeast culture by the method of the present invention, the crude protein content was 51.82%, the acid-soluble protein content was 26.03%, and the proportion of acid-soluble protein in crude protein was higher than 50%; the yeast count of the product reached 3.41×10 9 / g, and the mannan content was 1.79%; the result was similar to that in Example 1, indicating that the preparation method provided by the present invention is stable.

[0072] Example 3 Screening of raw material substrate ratio

[0073] 1. Materials

[0074] Corn gluten meal (dry, 10.2% moisture content), DDGS (dry, 11.5% moisture content).

[0075] 2. Test methods

[0076] 2.1 Corn gluten meal and DDGS were premixed in different proportions (Table 3) as fermentation raw materials, and enzyme preparations, yeasts and various auxiliary materials were added according to the addition ratios in Example 2 to perform aerobic fermentation and anaerobic fermentation on the raw materials. Finally, the products were dried at low temperature to obtain the products. The contents of crude protein, acid-soluble protein, mannan, organic acid and other nutrients in the products were sampled and determined, and the number of yeasts was detected after aerobic fermentation.

[0077] Each test group fermented 5 kg (dry basis) of raw materials in a shallow tray, and the fermentation process was shown in Example 2.

[0078] Table 3 Screening grouping of optimal addition ratio of raw material substrate

[0079]

[0080] 3. Results and Analysis

[0081] The nutrient contents of yeast cultures prepared with different ratios of raw materials as substrates are shown in Table 4.

[0082] Table 4 Effects of different ratios of corn gluten meal and DDGS raw materials on yeast culture

[0083]

[0084] As shown in Table 4, when the ratio of corn gluten meal to DDGS was 1-2:1, the crude protein after fermentation exceeded 51%, the acid-soluble protein solution was greater than 20%, the mannan content was greater than 1.5%, the yeast count reached 3 billion / g, and the organic acid content was greater than 5%, indicating that when the ratio of corn gluten meal to DDGS raw materials was 1-2:1, the final yeast culture obtained was not much different. When the ratio of the raw substrate corn gluten meal to DDGS was 1.5:1, the organic acid and mannan contents were the highest, 6.23% and 1.89% respectively, and the yeast count was also the highest, reaching 3.39×10 9 / g, indicating that this raw material ratio can obtain the most yeast biomass after fermentation, which is the most suitable raw material ratio. In this case, the crude protein of the yeast culture can reach 55.69%, the acid-soluble protein can reach 25.03%, and the ratio of acid-soluble protein to crude protein is 45%.

[0085] Example 4 Pilot test of high protein yeast culture

[0086] 1. Materials: 500 kg corn gluten meal (moisture content 45%), 800 kg DDGS (moisture content 65%).

[0087] 2. Production method

[0088] 2.1 Raw material mixing and inoculation

[0089] Wet corn gluten meal, wet DDGS, 1.2 kg of saccharifying enzyme (100,000 U / g), 3 kg of neutral protease (100,000 U / g), 3.5 kg of acid protease (50,000 U / g), 0.6 kg of hemicellulase (100,000 U / g), 0.35 kg of acid cellulase (20,000 U / g), 5.5 kg of urea, 15 kg of calcium carbonate and 3 kg of Aspergillus niger culture are mixed in batches in a mixer according to proportion, and 50 kg of yeast liquid (2 kg of active dry yeast powder activated by sugar water) is inoculated while mixing.

[0090] 2.2 Aerobic fermentation

[0091] The mixed materials are added into a fermentation tank with a stainless steel screen as the substrate. The pile height is 50 cm and forced ventilation is performed with a Roots blower. The air intake is adjusted according to the temperature of the fermented materials to ensure that the temperature of the upper layer of the materials is lower than 45°C. The materials are turned over every 4 hours to mix them evenly and water is added appropriately to keep the moisture content of the materials > 45%.

[0092] 2.3 Anaerobic fermentation

[0093] After 48 hours of aerobic fermentation, add 2.5 kg of glucose, 5 kg of acid protease (50,000 U / g), 2.5 kg of neutral protease (100,000 U / g), 3 kg of mannanase (50,000 U / g), and 1 kg of nuclease (50,000 U / g) to the material, inoculate 0.25 kg of Bacillus subtilis (100 billion CFU / g) and 0.5 kg of Bacillus coagulans (100 billion CFU / g) while mixing, mix well and put into the fermentation tank, stop ventilation after 30 minutes of small air volume, and ferment anaerobicly for 24 hours.

[0094] 2.4 Low temperature drying

[0095] The fermented material is dried in a fluidized bed, the material temperature is kept below 60°C, and the moisture content is <10%.

[0096] 3. Sample testing

[0097] The two raw materials and the dried yeast culture samples after fermentation were taken to determine the contents of crude protein, acid-soluble protein and mannan. During the fermentation process, samples were taken to count the number of yeast using a hemocytometer. At the same time, the contents of crude protein, acid-soluble protein, mannan and organic acid as well as the pH value were measured.

[0098] 4. Results and Analysis

[0099] The nutritional indexes of the yeast culture prepared with the wet raw materials as substrate are shown in Table 5, and the material detection during the yeast culture fermentation process is shown in Table 6.

[0100] Table 5 Nutrient composition index of yeast culture and raw materials

[0101]

[0102] Table 6 Material detection during yeast culture fermentation

[0103]

[0104]

[0105] As shown in Table 5, the crude protein content of the yeast culture obtained after pilot test using wet corn gluten meal and wet DDGS was 55.49%, the acid-soluble protein content was 26.03%, and the acid-soluble protein accounted for 50% of the crude protein; the yeast count of the product reached 3.50×109 The results were similar to those in Examples 1 and 2, indicating that the method was relatively stable.

[0106] Table 6 shows the changes in protein content, yeast count and organic acid content based on pH of the material during the fermentation process. During the aerobic fermentation stage, the rate of hydrolysis of corn protein into acid-soluble protein is fast at first and then slow, and the acid-soluble protein content can also be increased from 20.34% to 28.03% during the anaerobic fermentation stage. Yeast proliferation mainly occurs between 6 and 36 hours in the aerobic fermentation stage, accompanied by a rapid increase in mannan content and a decrease in organic acid content, which also leads to a continuous increase in the pH value of the material during the aerobic fermentation stage. During the anaerobic fermentation stage, accompanied by the production of organic acids and yeast autolysis, the pH value of the material rises, the number of complete yeast cells decreases, and the cell autolysis rate exceeds 60%.

[0107] Example 5 Effect of high-protein yeast culture replacing fish meal on growth performance and antioxidant indexes of large yellow croaker

[0108] 1. Materials and Methods

[0109] 450 yellow croakers with healthy body condition and similar weight were selected and divided into 3 treatments (control group, experimental group 1, and experimental group 2). Three cages were set up in each treatment, and 50 yellow croakers were raised in each cage. After two weeks of acclimatization, the test feed was fed twice a day for 60 days. The content of fish meal and high-protein yeast culture added in each treatment is as follows.

[0110] Control group: fish meal was used as the main protein raw material, and the formula contained 36% fish meal.

[0111] Experimental Group 1: High protein yeast culture replaced 5% fish meal (G1).

[0112] Experimental Group 2: High protein yeast culture replaced 10% of fish meal (G2).

[0113] 2. Sample Preparation

[0114] The high protein yeast culture prepared in Example 4.

[0115] 3. Determination indicators and methods

[0116] 3.1 Growth performance

[0117] The number of dead large yellow croakers in each cage was cleaned and recorded every day, and the survival rate was calculated. The weight of each fish was measured, and the survival rate, weight gain percentage and feed efficiency were calculated.

[0118] 3.2 Antioxidant index

[0119] Five samples were taken from each replicate for determination of antioxidant indexes. Superoxide dismutase (SOD), total antioxidant capacity (T-AOC), catalase (CAT) and malondialdehyde (MDA) were determined by enzyme-linked immunosorbent assay.

[0120] 3.3 Data processing

[0121] Statistical analysis and variance analysis of each element index were performed using Microsoft EXCEL 2010 software and IBM SPSS Statistics 26 software.

[0122] 4.Basic feed formula and ingredients

[0123] The basic feed formula is shown in Table 7.

[0124] Table 7 Basic feed formula and ingredients

[0125]

[0126] 5. Results and Analysis

[0127] 5.1 Effect of high-protein yeast culture replacing fish meal on the growth performance of large yellow croaker

[0128] Table 8 Effect of high protein yeast culture replacing fish meal on growth performance of large yellow croaker

[0129]

[0130] The effect of high-protein yeast culture replacing fish meal on the growth performance of large yellow croaker is shown in Table 8. In the conventional large yellow croaker feed formula, when high-protein yeast culture is used to replace fish meal, the survival rate of large yellow croaker can be significantly improved (p < 0.05), and the higher the addition amount, the higher the survival rate of large yellow croaker; when replacing 5% fish meal, the weight gain rate and feed conversion rate of large yellow croaker are not significantly different from those of the control group; and when replacing 10% fish meal, the weight gain rate of large yellow croaker is significantly reduced, and the feed conversion rate is also significantly reduced. It shows that the high-protein yeast culture of the present invention can be added to the formula to replace 5% fish meal without significant effect on the growth performance of large yellow croaker.

[0131] 5.2 Effect of high-protein yeast culture replacing fish meal on antioxidant indexes of large yellow croaker

[0132] Table 9 Effect of high-protein yeast culture replacing fish meal on antioxidant indexes of large yellow croaker

[0133]

[0134]

[0135] The effect of replacing fish meal with high-protein yeast culture on the antioxidant indexes of large yellow croaker is shown in Table 9. In the conventional large yellow croaker feed formula, when the high-protein yeast culture of the present invention replaces 5% and 10% of fish meal, the T-SOD and T-AOC indexes of the large yellow croaker are significantly improved, but the CAT activity is not significantly affected, and the MDA content is also significantly reduced. This shows that replacing 5% and 10% of fish meal with high-protein yeast culture can improve the antioxidant capacity of large yellow croaker and help maintain the health level of large yellow croaker.

[0136] Example 6 Effect of high-protein yeast culture replacing soybean enzymatic protein on weaned piglets

[0137] 1. Materials and Methods

[0138] 640 weaned piglets with healthy body condition and similar body weight were selected and divided into two treatment groups (control group and experimental group), with 16 pens in each group and 20 pigs in each pen. They were fed three times a day and had free access to food and water for 42 days. The dietary formulas of the two groups are shown in Table 10.

[0139] Table 10 Basic feed formula and ingredients

[0140]

[0141] 2. Sample Preparation

[0142] The high protein yeast culture prepared in Example 4.

[0143] 3. Test results

[0144] The experiment was divided into three stages: 1-14 days, 15-18 days and 19-42 days. The daily weight gain, feed intake and weight gain / feed intake data of each group were counted respectively. The results are shown in Table 11.

[0145] Table 11 Effect of high-protein yeast culture replacing soybean enzymatic protein on piglet growth performance

[0146]

[0147]

[0148] The results showed that adding 5% high-protein yeast culture to piglet feed to replace soy enzymatic protein had no significant effect on their growth performance at all stages from 1 to 42 days after weaning, and could slightly increase the average daily weight gain of weaned piglets and improve feed conversion efficiency from 15 to 28 days.

[0149] Example 7 Effect of high protein yeast culture replacing fish meal on white shrimp

[0150] 1. Materials and Methods

[0151] The white shrimp were cultured in a constant temperature circulating water pond with an initial average body weight of 0.25 g. They were divided into an experimental group and a control group, each with 6 ponds, and fed for 6 weeks. The daily diet formulas of the two groups are shown in Table 12.

[0152] Table 12 Basic feed formula and ingredients

[0153]

[0154] 2. Sample Preparation

[0155] The high-protein yeast culture prepared in Example 4.

[0156] 3. Test results

[0157] After the 6-week trial period, the shrimps were collected, weighed, and the weight gain rate and survival rate were calculated. The results are shown in Table 13.

[0158] Table 13 Effect of high protein yeast culture replacing fish meal on the production performance of white shrimp

[0159]

[0160] The results showed that adding 6% high-protein yeast culture to shrimp feed to replace fish meal in equal amounts can increase the specific growth rate of shrimp fry and help improve the survival rate of shrimp fry.

[0161] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a yeast culture with a high protein content, characterized in that: The following steps are involved: First, DDGS and corn gluten powder are mixed, then enzyme preparation 1, yeast and auxiliary materials are added for the first fermentation, and finally Bacillus subtilis, Bacillus coagulans, glucose and enzyme preparation 2 are added for the second fermentation to obtain the yeast culture.

2. The preparation method according to claim 1, characterized in that: Calculated by mass ratio, the ratio of the DDGS to the corn gluten meal is 1:1-2.

3. The preparation method according to claim 1, characterized in that: The enzyme preparation 1 comprises saccharifying enzyme, neutral protease, acid protease, Aspergillus niger culture, hemicellulase and acid cellulase.

4. The preparation method according to claim 3, characterized in that: The added amount of saccharifying enzyme is 200-500U / g, the added amount of neutral protease is 500-1000U / g, the added amount of acid protease is 300-600U / g, the added amount of Aspergillus niger culture is 0.5-1%, the added amount of hemicellulase is 100-200U / g and the added amount of acid cellulase is 20-50U / g.

5. The preparation method according to claim 1, characterized in that: The auxiliary materials include urea and calcium carbonate; the addition amount of the yeast is 0.5-1×10 8 Pieces / g.

6. The preparation method according to claim 1, characterized in that: The inoculation amounts of the Bacillus subtilis and the Bacillus coagulans are 0.1-0.5×10 8 / g and 0.5-1×10 8 The amount of glucose added is 0.5-2%, and the enzyme preparation 2 includes acid protease, neutral protease, mannanase and nuclease.

7. The preparation method according to claim 6, characterized in that: The added amount of the acidic protease is 100-500 U / g, the added amount of the neutral protease is 300-500 U / g, the added amount of the mannanase is 100-300 U / g, and the added amount of the nuclease is 5-10 U / g.

8. The yeast culture obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the yeast culture according to claim 8 in improving feed efficiency.

10. Use of the yeast culture according to claim 8 in improving animal production performance.

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