A preparation method of yeast protein based on alcohol waste liquid fermentation production

Abstract

The present application relates to high protein fermentation technical field, specifically disclose a kind of preparation method for fermenting production of yeast protein based on alcohol waste liquor, to solve the technical problems such as low utilization rate of alcohol waste liquor resource, feed soybean meal supply is nervous and high cost.The method includes the following steps: first, the alcohol waste liquor produced by grain deep processing is concentrated to dry basis content ≥30%, the composite carbon source carrier is crushed, urea and molasses are added to adjust the carbon-nitrogen ratio to (20~25):1, access to the complex fermentation strain containing Candida utilis, solid fermentation is carried out, and the finished product yeast protein is obtained.The present application uses solid fermentation mode, matches composite carbon source carrier to optimize nutrient ratio, step by step controls key process parameters, and the finished product yeast protein is ≥24%, true protein is ≥22%, and nitrogen conversion rate is ≥85%, which can replace soybean meal as feed additive.The method realizes alcohol waste liquor resource utilization, pollution is small, reduces feeding cost, has environmental protection and economic value, and is suitable for industrialization popularization and application.

Description

Technical Field

[0001] This invention belongs to the field of alcohol fermentation technology and relates to a method for preparing yeast protein based on the fermentation of alcohol waste liquid. Background Technology

[0002] The deep processing of grains generates a large amount of alcohol waste liquid. This waste liquid is rich in carbohydrates, proteins, amino acids, vitamins, and various minerals such as nitrogen, phosphorus, and potassium, representing a potential high-quality nutritional resource. However, currently, most alcohol waste liquid is discharged after only simple treatment or disposed of at low prices, resulting in the waste of nutrients and pollution of water bodies and soil, which does not meet the development requirements of environmental protection and resource utilization. Meanwhile, soybean meal, as a core plant protein raw material in the feed industry, experiences significant price fluctuations due to market supply and demand, and its limited production makes it difficult to meet the needs of large-scale farming. Therefore, developing low-cost, high-quality feed protein raw materials that can replace soybean meal has become an urgent need for the industry.

[0003] Yeast protein, as a high-quality single-cell protein, boasts advantages such as rich nutrition, easy digestibility and absorption, and controllable production costs. It can effectively replace soybean meal in feed production. Utilizing alcohol waste liquid for fermentation to produce yeast protein not only achieves resource utilization of alcohol waste liquid, solving its environmental pollution problem, but also produces low-cost feed protein, alleviating the current tight supply of soybean meal, thus possessing both environmental and economic value. Currently, there are related studies on the fermentation of alcohol waste liquid to produce yeast protein, but most processes use liquid fermentation methods, which suffer from high energy consumption, susceptibility to microbial contamination, difficulty in subsequent solid-liquid separation, and low nitrogen conversion rates. Furthermore, some processes fail to properly control key parameters such as the carbon-to-nitrogen ratio, pH, and water content, resulting in low yeast protein yield and unstable product quality, hindering industrial application.

[0004] Therefore, there is an urgent need to develop a protein feed based on solid-state fermentation technology that can achieve high nitrogen conversion rate, high quality and stable performance by precisely controlling the fermentation microenvironment, so as to effectively replace soybean meal. Summary of the Invention

[0005] In view of the above-mentioned defects in the prior art, the purpose of this invention is to provide a method for preparing yeast protein based on the fermentation of alcohol waste liquid.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing yeast protein based on the fermentation of alcohol waste liquid includes the following steps: S1. Concentrate the alcohol waste liquid generated from deep grain processing, wherein the dry basis content of the concentrated alcohol waste liquid is ≥30%; S2. Pre-treat the carbon source carrier by crushing it to 50-70 mesh to obtain carbon source carrier particles; S3. Mix the concentrated alcohol waste liquid from step S1 and the pretreated carbon source carrier particles from step S2 evenly to obtain mixture A, wherein the water content of mixture A is ≤50%; S4. Add urea and molasses to the above mixture A to obtain mixture B; the carbon-to-nitrogen ratio of mixture B is (20~25):1; S5. Add distilled water to mixture B and mix thoroughly. Adjust the pH to 6-7 to obtain the fermentation raw material; the water content of the fermentation raw material is 60-70%. S6. Inoculate the above-mentioned fermentation raw materials with a compound fermentation strain containing Candida utilis and carry out solid-state fermentation; the viable count of the compound fermentation strain is ≥1×10⁻⁶. 9 CFU / g; S7. After fermentation is complete, dry the product and pass it through a 20-40 mesh sieve to obtain a finished yeast protein product with a moisture content of ≤10%.

[0007] Preferably, the grain used for the alcohol waste liquid in step S1 is any one of wheat, corn, soybean, sorghum and rice; the carbon source carrier in step S2 is one of corn cob, wheat bran, potato residue or straw powder or a mixture of multiple types in any proportion.

[0008] Preferably, the mass ratio of carbon source carrier particles, urea and molasses in steps S3 and S4 is (80~90):(3~5):(1~3).

[0009] Preferably, when adding urea to mixture A in step S4, it is added in two parts: 70% of the total amount of urea is added first, and the remaining 30% is added 12 hours later.

[0010] Preferably, the carbon-to-nitrogen ratio of mixture B in step S4 is (20~25):1.

[0011] Preferably, the drying temperature in step S7 is 55~65℃ and the drying time is 6~12h.

[0012] Preferably, the solid-state fermentation operation method in step S6 is as follows: S601. Place the fermentation raw material on the fermentation bed, wherein the thickness of the fermentation raw material is 15~25cm; S602. Inoculate the above-mentioned fermentation raw materials with compound fermentation bacteria to obtain pretreated compound fermentation substrate; S603. The pretreated compound fermentation substrate is subjected to low-temperature segmented fermentation at 30~35℃. During the fermentation process, the substrate is turned intermittently, once every 12 hours. After the fermentation is completed, the substrate is allowed to cool down naturally.

[0013] Preferably, the mass fraction of the compound fermentation strain in step S6 is 8-12%.

[0014] Preferably, the compound fermentation strain is a mixture of Candida utilis, Aspergillus niger and Bacillus subtilis in a mass ratio of (2~4):(1~3):(0.5~2).

[0015] Preferably, the low-temperature segmented fermentation is divided into early fermentation and late fermentation. The early fermentation temperature is 30~32℃ and the fermentation time is 2~4 days; the late fermentation temperature is 33~35℃ and the fermentation time is 3~5 days.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) The yeast protein prepared by this method has high application value. Through various technical indicators, it has been proven that it can effectively replace soybean meal for feeding. The preparation method is simple and suitable for industrial production.

[0017] (2) This method realizes the efficient resource utilization of alcohol waste liquid, with concentrated alcohol waste liquid as the core matrix, combined with agricultural by-product carbon source carrier, reducing environmental pollution and nutrient waste.

[0018] (3) This process uses solid fermentation technology instead of liquid fermentation, which can make full use of raw materials such as alcohol waste liquid and agricultural by-products, reduce wastewater generation, effectively simplify subsequent treatment, reduce environmental protection investment, and conform to the concept of green circular economy. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] To achieve the above-mentioned objectives of the present invention, the technical solution of the present invention will be further described in detail below, but the scope of protection of the present invention is not limited to the following description.

[0021] A method for producing yeast protein based on the fermentation of alcohol waste liquid includes pretreatment of raw materials and solid-state fermentation, specifically including the following steps: S1. The alcohol waste liquid generated during the deep processing of grain is concentrated, and the dry basis content of the concentrated alcohol waste liquid is ≥30%; in some embodiments, the grain used for the deep processing of grain is corn; in other embodiments, it is at least one of wheat, soybean and sorghum; S2. The carbon source carrier is pretreated and crushed to 50-70 mesh to obtain uniform carbon source carrier particles; in some embodiments, the carbon source carrier is corn cob; in other embodiments, it is at least one of wheat bran, potato residue and straw. Using the above four raw materials as carbon source carriers can provide both fast-acting carbon sources that can be utilized quickly and slow-release carbon sources that can be supported. Furthermore, the combination of crude fiber, protein, and inorganic nutrients is balanced, which can provide stable and comprehensive matrix support for microbial growth and metabolism, nutrient fixation, and subsequent resource utilization.

[0022] S3. Mix the concentrated alcohol waste liquid from step S1 and the pretreated carbon source carrier particles from step S2 evenly to obtain mixture A, wherein the water content of mixture A is ≤50%; Controlling the moisture content of mixture A is mainly to avoid problems such as anaerobic odor, clumping, and poor air permeability caused by excessive moisture content. At the same time, it ensures that the material has good looseness and pore structure, maintains a suitable aerobic environment to promote microbial growth, metabolism, and nutrient conversion. Lower moisture content can also inhibit the growth of miscellaneous bacteria and harmful microorganisms, reduce nutrient loss, improve system stability, facilitate subsequent fermentation, granulation, storage, transportation, and resource utilization, and prevent material spoilage.

[0023] S4. Add urea and molasses to the above mixture A to obtain mixture B; the carbon-nitrogen ratio of the mixture B is (20~25):1; the mass ratio of the carbon source carrier particles to urea and molasses in step S3 is (80~90):(3~5):(1~3); By supplementing the system with urea as a readily available nitrogen source and molasses as a readily available carbon source, the carbon-nitrogen ratio is brought to a suitable range for microbial growth and reproduction. This optimizes the nutrient ratio structure, meets the synergistic needs of microbial metabolism and fermentation for carbon and nitrogen nutrition, improves fermentation efficiency, promotes rapid decomposition and transformation of organic matter and nutrient solidification, and enhances the maturity and stability of the material. It also prevents slow fermentation, insufficient temperature rise, off-odors, or nutrient loss caused by an imbalance in the carbon-nitrogen ratio, thus laying a good substrate condition for subsequent molding, storage, and resource utilization.

[0024] S5. Add distilled water to mixture B and mix thoroughly. Adjust the pH to 6-7 to obtain the fermentation raw material; the water content of the fermentation raw material is 60-70%. This process transforms the material from a low-moisture solid state to a high-moisture humid state, creating a liquid environment conducive to rapid microbial proliferation and vigorous metabolic activity. This ensures the full dissolution, diffusion, and transfer of nutrients, enhancing the absorption and utilization efficiency of carbon, nitrogen, and trace elements by the microorganisms. Maintaining the pH of the system at 6-7 is primarily to create a neutral to slightly acidic environment optimal for microbial growth and metabolism, preventing excessive acidity or alkalinity from inhibiting intracellular enzyme activity and ensuring efficient absorption and conversion of carbon, nitrogen, and other nutrients by the microorganisms. Simultaneously, it stabilizes the fermentation system and reduces the growth of harmful bacteria.

[0025] S6. Inoculate the above-mentioned fermentation raw materials with a compound fermentation strain containing Candida utilis and carry out solid-state fermentation; The viable count of the compound fermentation strain is ≥1×10⁻⁶. 9 CFU / g; the mass fraction of the compound fermentation strain is 8~12%; the compound fermentation strain is a mixture of Candida utilis, Aspergillus niger and Bacillus subtilis in a mass ratio of (2~4):(1~3):(0.5~2); The specific operation method of the solid-state fermentation is as follows: S601. Place the fermentation raw materials on the fermentation bed, wherein the thickness of the fermentation raw material layer is 15~25cm; S602. Inoculate the above-mentioned fermentation raw materials with compound fermentation bacteria to obtain pretreated compound fermentation substrate; S603. The pretreated compound fermentation substrate is subjected to low-temperature segmented fermentation. The initial fermentation temperature is 30~32℃ and the fermentation time is 2~4 days. The later fermentation temperature is 33~35℃ and the fermentation time is 3~5 days. During the fermentation process, the substrate is turned intermittently, once every 12 hours.

[0026] S7. After fermentation is complete, dry at 55~65℃ and pass through a 20~40 mesh sieve to obtain finished yeast protein with a moisture content of ≤10%.

[0027] Controlling moisture content can effectively inhibit the growth and reproduction of harmful microorganisms such as mold and bacteria, and prevent products from becoming moldy, deteriorating, clumping, and degrading in nutrients during storage and transportation.

[0028] Example 1 A method for producing yeast protein based on the fermentation of alcohol waste liquid includes pretreatment of raw materials and solid-state fermentation, specifically including the following steps: S1. Concentrate the alcohol waste liquid generated during corn deep processing to a dry basis content of 30%; S2. Pre-treat the corn cobs by passing them through a 60-mesh sieve to obtain uniform corn cob particles. S3. Mix the concentrated alcohol waste liquid from step S1 and the corn cob particles from step S2 evenly to obtain mixture A, wherein the water content of mixture A is 48%; S4. Add urea and molasses to the above mixture A to obtain mixture B. The carbon-nitrogen ratio of mixture B is 22:1, and the mass ratio of corn cob particles, urea and molasses in step S3 is 85:4:2. S5. Add distilled water to mixture B and mix well. Adjust the pH to 6.5 to obtain a fermentation raw material with a water content of 65%. S6. Inoculate the above-mentioned fermentation raw materials with a compound fermentation strain containing Candida utilis and carry out solid-state fermentation; The viable count of the compound microbial strain is ≥1×10⁻⁶. 9CFU / g; the mass fraction of the compound fermentation strain is 10%; the compound fermentation strain is a mixture of Candida utilis, Aspergillus niger and Bacillus subtilis in a mass ratio of 3:2:1.5; The specific operation method of the solid-state fermentation is as follows: S601. Place the fermentation raw materials on the fermentation bed, wherein the thickness of the fermentation raw material layer is 20cm; S602. Inoculate the above-mentioned fermentation raw materials with compound fermentation bacteria to obtain pretreated compound fermentation substrate; S603. The pretreated compound fermentation substrate is subjected to low-temperature segmented fermentation. The initial fermentation temperature is 31℃ and the fermentation time is 3 days. The later fermentation temperature is 34℃ and the fermentation time is 4 days. During the fermentation process, the substrate is turned over intermittently once every 12 hours. S7. After fermentation is complete, dry at 60℃ and pass through a 30-mesh sieve to obtain a finished yeast protein with a water content of 8.5%.

[0029] Example 2 A method for producing yeast protein based on the fermentation of alcohol waste liquid includes pretreatment of raw materials and solid-state fermentation, specifically including the following steps: S1. Concentrate the alcohol waste liquid generated during the deep processing of wheat to a dry basis content of 32%; S2. Crush the wheat bran and pass it through a 60-mesh sieve to obtain uniform wheat bran particles. S3. Mix the concentrated alcohol waste liquid from step S1 and the wheat bran particles from step S2 evenly to obtain mixture A, wherein the water content of mixture A is 45%; S4. Add urea and molasses to the above mixture A to obtain mixture B. The carbon-nitrogen ratio of mixture B is 20:1, and the mass ratio of wheat bran particles, urea and molasses in step S3 is 88:3:2. S5. Add distilled water to mixture B and mix well. Adjust the pH to 6.0 to obtain a fermentation raw material with a water content of 62%. S6. Inoculate the above-mentioned fermentation raw materials with a compound fermentation strain containing Candida utilis and carry out solid-state fermentation; The viable count of the compound microbial strain is ≥1×10⁻⁶. 9 CFU / g; the mass fraction of the compound fermentation strain is 8%; the compound fermentation strain is a mixture of Candida utilis, Aspergillus niger and Bacillus subtilis in a mass ratio of 4:3:2; The specific operation method of the solid-state fermentation is as follows: S601. Place the fermentation raw materials on the fermentation bed, wherein the thickness of the fermentation raw material layer is 15cm; S602. Inoculate the above-mentioned fermentation raw materials with compound fermentation bacteria to obtain pretreated compound fermentation substrate; S603. The pretreated compound fermentation substrate is subjected to low-temperature segmented fermentation. The initial fermentation temperature is 33℃ and the fermentation time is 2 days. The later fermentation temperature is 35℃ and the fermentation time is 5 days. During the fermentation process, the substrate is turned intermittently once every 12 hours.

[0030] S7. After fermentation is complete, dry at 55℃ and pass through a 20-mesh sieve to obtain the finished yeast protein with a water content of 9.2%.

[0031] Example 3 A method for producing yeast protein based on the fermentation of alcohol waste liquid includes pretreatment of raw materials and solid-state fermentation, specifically including the following steps: S1. Concentrate the alcohol waste liquid generated during the deep processing of soybeans to a dry basis content of 35%; S2. Pre-treat the straw by passing it through a 70-mesh sieve to obtain uniform straw powder; S3. Mix the concentrated alcohol waste liquid from step S1 and the straw powder from step S2 evenly to obtain mixture A, wherein the water content of mixture A is 42%; S4. Add urea and molasses to the above mixture A to obtain mixture B. The carbon-nitrogen ratio of mixture B is 25:1, and the mass ratio of straw powder, urea and molasses in step S3 is 82:5:3. S5. Add distilled water to mixture B and mix well. Adjust the pH to 7.0 to obtain a fermentation raw material with a water content of 70%. S6. Inoculate the above-mentioned fermentation raw materials with a compound fermentation strain containing Candida utilis and carry out solid-state fermentation; The viable count of the compound microbial strain is ≥1×10⁻⁶. 9 CFU / g; the mass fraction of the compound fermentation strain is 12%; the compound fermentation strain is a mixture of Candida utilis, Aspergillus niger and Bacillus subtilis in a mass ratio of 2:1:0.5; The specific operation method of the solid-state fermentation is as follows: S601. Place the fermentation raw materials on the fermentation bed, wherein the thickness of the fermentation raw material layer is 25cm; S602. Inoculate the above-mentioned fermentation raw materials with compound fermentation bacteria to obtain pretreated compound fermentation substrate; S603. The above-mentioned pretreated compound fermentation substrate is subjected to low-temperature segmented fermentation. The initial fermentation temperature is 30℃ and the fermentation time is 4 days; the later fermentation temperature is 33℃ and the fermentation time is 3 days. During the fermentation process, the substrate is turned intermittently once every 12 hours.

[0032] S7. After fermentation is complete, dry at 65℃ and pass through a 40-mesh sieve to obtain the finished yeast protein with a water content of 7.8%.

[0033] Comparative Example 1 Compared with Example 1, the carbon-nitrogen ratio (C / N) in step S4 was adjusted to 15:1, which is lower than the carbon-nitrogen ratio (C / N=(20~25):1) in Example 1. The other parameters are completely consistent with Example 1.

[0034] Comparative Example 2 Compared with Example 1, the key yeast (Candida utilis) was removed from the compound fermentation strain described in step S6. The compound fermentation strain is composed of Aspergillus niger and Bacillus subtilis in a mass ratio of 4:2.5. The remaining parameters are completely consistent with those of Example 1.

[0035] Comparative Example 3 Compared with Example 1, only the solid fermentation in step S6 is changed to liquid fermentation, and the other parameters are completely the same as in Example 1.

[0036] The specific operation method for liquid fermentation is as follows: S601. Place the fermentation raw materials from step S5 into a fermentation tank, and then add distilled water to obtain a liquid fermentation system. S602. Inoculate the above-mentioned liquid fermentation system with compound fermentation bacteria to obtain pretreated compound fermentation substrate; S603. The above-mentioned pretreated compound fermentation substrate is subjected to low-temperature segmented fermentation. The initial fermentation temperature is 30℃ and the fermentation time is 3 days; the later fermentation temperature is 33℃ and the fermentation time is 4 days. During the fermentation process, the substrate is not turned over, but instead ventilated and stirred in the tank.

[0037] Comparative Example 4 Compared with Example 1, when feeding cattle, the yeast protein of the present invention was replaced with an equal mass of soybean meal.

[0038] Comparative Example 5 Compared with Comparative Example 4, the amount of soybean meal used was reduced by 20%.

[0039] Comparative Example 6 Compared with Comparative Example 4, the amount of soybean meal used was increased by 20%.

[0040] The yeast protein prepared by this invention is applied to ruminants. Taking cattle as an example, there are a total of 9 groups of examples and comparative examples. Each group includes calves, medium cattle and large cattle. Three cattle of each type are selected. The comparison is mainly based on the performance indicators and feed conversion rate of the yeast protein in Table 1.

[0041] The prepared yeast protein is compounded with feed (including concentrate and roughage) at a mass ratio of (1~3):(7~9) to obtain a compound feed, specifically: 1) Calf: Yeast protein: Feed = 3:7; 2) Medium-sized cattle: yeast protein: feed = 2:8; 3) The ratio of adult cattle: yeast protein: feed is 1:9; Yeast protein was applied to cattle of different weights and fed according to their weight, specifically divided into the following three categories: 1) Calves (110~240kg): 250~400g / day; 2) Medium-sized cattle (241~420kg): 401~800g / day; 3) Large cattle (421~600kg): 801~1200g / day.

[0042] Conversion rate is a key technical indicator for evaluating weight gain, and the formula is as follows: As shown in Table 1, the crude fiber content in Examples 1-3 is ≤18%, proving that the yeast protein meets the standards for use as a concentrated feed. The crude protein content is ≥24% and the true protein content is ≥22%, proving that the yeast protein, as a protein source, can meet certain nutritional requirements. The residual urea content is ≤0.5%, indicating that the yeast protein provides a safety guarantee for animal consumption. The moisture content is ≤10%, ensuring the stability of the yeast protein in the market. The above data prove that the yeast protein prepared by this invention is safe and qualified to replace soybean meal in cattle formulas. Whether it can truly and effectively replace soybean meal in specific applications is shown in Table 2.

[0043] The data from Examples 1-3 demonstrate the scientific validity and reliability of this preparation process, enabling the stable production of high-quality yeast protein. However, Comparative Example 1, with a carbon-to-nitrogen ratio far below the recommended range (C / N = (20-25):1), showed a significant decrease in crude protein, true protein content, and nitrogen conversion rate, and also exhibited excessive residual urea. Comparative Example 2 showed a nitrogen conversion rate of only 65.8%, presumably due to the ineffective participation of *Candida utilis* in fermentation, thus reducing overall microbial fermentation efficiency. Comparative Example 3, using liquid fermentation instead of solid-state fermentation, had insufficient nutrient conversion efficiency, resulting in lower nitrogen conversion rate and protein content compared to the Example groups. Therefore, the preparation process employed in this invention, by optimizing the carbon-to-nitrogen ratio, fermentation method, and strain ratio, can significantly improve the yield efficiency and quality of yeast protein, ensuring that the product meets the standards of high protein, low residue, and high utilization rate.

[0044] Table 2. Comparison of application performance indicators of yeast protein prepared in Examples 1-3 and commercially available soybean meal in Comparative Examples 4-6. Assuming consistent feeding amounts, the data in Table 2 show that the feed conversion ratios of Examples 1-3 were 2.0-2.7, significantly lower than the 2.9-3.4 of Comparative Examples 4-6. The experimental results indicate that the yeast protein prepared in this invention can not only effectively replace soybean meal in cattle feeding, but also outperforms soybean meal in improving feed utilization efficiency.

[0045] Finally, it should be noted that although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A method for preparing yeast protein based on the fermentation of alcohol waste liquid, characterized in that, Includes the following steps: S1. Concentrate the alcohol waste liquid generated from deep grain processing, wherein the dry basis content of the concentrated alcohol waste liquid is ≥30%; S2. Pre-treat the carbon source carrier by crushing it to 50-70 mesh to obtain carbon source carrier particles; S3. Mix the concentrated alcohol waste liquid from step S1 and the pretreated carbon source carrier particles from step S2 evenly to obtain mixture A, wherein the water content of mixture A is ≤50%; S4. Add urea and molasses to the above mixture A to obtain mixture B; S5. Add distilled water to mixture B and mix thoroughly. Adjust the pH to 6-7 to obtain the fermentation raw material; the water content of the fermentation raw material is 60-70%. S6. Inoculate the above-mentioned fermentation raw materials with a compound fermentation strain containing Candida utilis and carry out solid-state fermentation; the viable count of the compound fermentation strain is ≥1×10⁻⁶. 9 CFU / g; S7. After fermentation is complete, dry the product and pass it through a 20-40 mesh sieve to obtain a finished yeast protein product with a moisture content of ≤10%.

2. The method for preparing yeast protein based on fermentation of alcohol waste liquid according to claim 1, characterized in that, The grain used for the alcohol waste liquid in step S1 is any one of wheat, corn, soybean, sorghum or rice; the carbon source carrier in step S2 is one of corn cob, wheat bran, potato residue or straw or a mixture of multiple types in any proportion.

3. The method for preparing yeast protein based on fermentation of alcohol waste liquid according to claim 1, characterized in that, The mass ratio of carbon source carrier particles, urea and molasses in steps S3 and S4 is (80~90):(3~5):(1~3).

4. The method for preparing yeast protein based on fermentation of alcohol waste liquid according to claim 3, characterized in that, When adding urea to mixture A in step S4, it is added in two parts. The first part is 70% of the total amount of urea, and the remaining 30% is added 12 hours later.

5. The method for preparing yeast protein based on fermentation of alcohol waste liquid according to claim 1, characterized in that, The carbon-to-nitrogen ratio of mixture B in step S4 is (20~25):

1.

6. The method for preparing yeast protein based on fermentation of alcohol waste liquid according to claim 1, characterized in that, The drying temperature in step S7 is 55~65℃ and the drying time is 6~12h.

7. The method for preparing yeast protein based on fermentation of alcohol waste liquid according to any one of claims 1 to 6, characterized in that, The solid-state fermentation operation method described in step S6 is as follows: S601. Place the fermentation raw material on the fermentation bed, wherein the thickness of the fermentation raw material is 15~25cm; S602. Inoculate the above-mentioned fermentation raw materials with compound fermentation bacteria to obtain pretreated compound fermentation substrate; S603. The pretreated compound fermentation substrate is subjected to low-temperature segmented fermentation at 30~35℃. During the fermentation process, the substrate is turned intermittently, once every 12 hours. After the fermentation is completed, the substrate is allowed to cool down naturally.

8. The method for preparing yeast protein based on fermentation of alcohol waste liquid according to claim 7, characterized in that, The mass fraction of the compound fermentation strain mentioned in step S6 is 8-12%.

9. The method for preparing yeast protein based on fermentation of alcohol waste liquid according to claim 8, characterized in that, The compound fermentation strain is composed of Candida utilis, Aspergillus niger and Bacillus subtilis in a mass ratio of (2~4):(1~3):(0.5~2).

10. The method for preparing yeast protein based on fermentation of alcohol waste liquid according to claim 7, characterized in that, The low-temperature segmented fermentation is divided into early fermentation and late fermentation. The early fermentation temperature is 30~32℃ and the fermentation time is 2~4 days; the late fermentation temperature is 33~35℃ and the fermentation time is 3~5 days.

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