Biological pretreatment method for improving the efficiency of producing true protein from wet white liquor residue

Abstract

The application discloses a biological pretreatment method for improving the efficiency of producing true protein from wet distiller's grains, and belongs to the technical field of biological pretreatment, which comprises the following steps: by combining chemical and biological multi-stage pretreatment methods, alkali and urea are used in the first chemical treatment process to realize better destruction of the fiber structure of the wet distiller's grains at normal temperature and reduce the contamination of miscellaneous bacteria in subsequent fermentation; the second anaerobic fermentation treatment converts the fibers in the wet distiller's grains into sugar through the synergistic effect of bacteria and enzymes, and reduces the pH of the wet distiller's grains, thereby providing conditions for the growth of Candida utilis in subsequent aerobic fermentation; and the third aerobic fermentation treatment utilizes the urea and fiber degradation sugar in the previous pretreatment process to generate cell protein, effectively improves the true protein improvement rate and fiber degradation rate of the distiller's grains after the pretreatment is completed, greatly reduces the loss rate in the pretreatment process, and finally improves the efficiency of producing true protein from the wet distiller's grains.

Description

Technical Field

[0001] This invention belongs to the field of biological pretreatment technology, specifically a biological pretreatment method to improve the efficiency of producing true protein from wet liquor lees. Background Technology

[0002] Soybean meal is the main byproduct of soybean oil extraction. Due to its high protein content (usually 43%-48%) and relatively balanced amino acid composition, it is an indispensable plant protein raw material in my country's feed industry, accounting for more than 60% of the total amount of feed protein raw materials used.

[0003] In recent years, with the rapid development of modern biosynthesis technology, "getting protein from microorganisms" has become a reality. Therefore, using feed microbial factories to convert resources such as wet distiller's grains into high-quality new feed protein feeds is of great significance for alleviating the pressure of soybean protein shortage in my country and developing new types of livestock productivity.

[0004] Currently, research on baijiu (Chinese liquor) lees mainly focuses on the treatment of dried baijiu lees, while research on the direct biotransformation of wet baijiu lees is limited. The main obstacles are the large number of miscellaneous bacteria and the high loss rate during fermentation pretreatment. Although baijiu lees contain some crude protein, only about 70% of this crude protein is true protein, severely impacting the protein quality. Furthermore, baijiu lees are rich in cellulose. If this cellulose can be converted into fermentable sugars through efficient degradation technology, it can serve as a carbon source for synthesizing microbial proteins. Among existing cellulose degradation methods, chemical methods are relatively inexpensive but often require high temperature and pressure conditions, resulting in high energy consumption and environmental pollution.

[0005] Therefore, developing an efficient, feasible, and applicable biological pretreatment process for wet baijiu lees to improve its true protein production efficiency has significant application value and practical significance. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention aims to provide a biological pretreatment method for improving the efficiency of true protein production from wet distillery waste. This method combines chemical and biological multi-stage pretreatment. In the first stage of chemical treatment, alkali and urea are used in combination to break down the fiber structure of the wet distillery waste at room temperature and reduce contamination by other microorganisms during subsequent fermentation. In the second stage of anaerobic fermentation, the synergistic action of bacteria and enzymes converts the fiber in the wet distillery waste into sugars and lowers the pH of the waste, providing conditions for the growth of Candida utilis cells in subsequent aerobic fermentation. In the third stage of aerobic fermentation, Candida utilis cells utilize the urea and fiber from the previous pretreatment to degrade sugars and generate cell protein. This effectively improves the true protein yield and fiber degradation rate of the distillery waste after pretreatment, reduces the loss rate during pretreatment, and ultimately improves the efficiency of true protein production from wet distillery waste, providing a solution for replacing a certain proportion of soybean meal in livestock and poultry feed formulations.

[0007] To achieve the above-mentioned objectives, the present invention is implemented through the following technical solution:

[0008] A biological pretreatment method for improving the efficiency of true protein production from wet baijiu lees includes the following steps:

[0009] A. Chemical treatment: After mixing the wet white wine lees, calcium hydroxide and urea evenly, seal and place in a constant temperature environment for chemical treatment;

[0010] B. Preparation of bacterial enzyme solution: Dissolve Pyrococcus lactis, cellulase and protease in water and stir evenly to obtain bacterial enzyme solution;

[0011] C. Anaerobic fermentation treatment: After the enzyme solution prepared in step B is evenly sprayed onto the bran, it is then mixed evenly with the chemically treated baijiu lees in step A, and sealed for anaerobic fermentation in a constant temperature environment of 37℃ for 72 hours.

[0012] D. Aerobic fermentation treatment: Dissolve 1-5 parts of Candida utilis in 15-19 parts of water to form a yeast liquid, and then inoculate it into 880-1000 parts of the baijiu lees that have undergone anaerobic fermentation in step C. Then, aerobic fermentation is carried out in an open environment at 30℃ for 72 hours.

[0013] In a preferred embodiment of this application, in step A of the biological pretreatment method for improving the efficiency of true protein production from wet liquor lees, the wet liquor lees are 790-854 parts by weight, calcium hydroxide is 5-50 parts by weight, and urea is 1-20 parts by weight; more preferably, the wet liquor lees are 832 parts by weight, calcium hydroxide is 21 parts by weight, and urea is 7 parts by weight.

[0014] In a preferred embodiment of this application, in step A of the biological pretreatment method for improving the efficiency of producing true protein from wet baijiu lees, the temperature during chemical treatment is 30±2℃ and the treatment time is 48±2h.

[0015] In a preferred embodiment of this application, in step B of the biological pretreatment method for improving the efficiency of true protein production from wet baijiu lees, the following components are present by weight: 0.1-1 parts of Pediococcus lactis, 1-5 parts of cellulase, 0.1-2 parts of protease, and 12-18.8 parts of water; more preferably, 0.1 parts of Pediococcus lactis, 2 parts of cellulase, 0.2 parts of protease, and 17.7 parts of water.

[0016] In a preferred embodiment of this application, in step B of the biological pretreatment method for improving the efficiency of producing true protein from wet baijiu lees, the viable count of Pediococcus lactis is ≥10 billion CFU / g, the cellulase activity is ≥50,000 U / g, and the protease activity is ≥10,000 U / g.

[0017] In a preferred embodiment of this application, in step C of the biological pretreatment method for improving the efficiency of true protein production from wet baijiu lees, the proportions by weight are: 13-27 parts of bacterial enzyme solution, 50-150 parts of wheat bran, and 823-937 parts of wet baijiu lees chemically treated in step A; more preferably, the proportions are: 20 parts of bacterial enzyme solution, 100 parts of wheat bran, and 860 parts of wet baijiu lees chemically treated in step A.

[0018] In a preferred embodiment of this application, in step C of the biological pretreatment method for improving the efficiency of true protein production from wet baijiu lees, the temperature of sealed anaerobic fermentation is 37±2℃ and the time of anaerobic fermentation is 72±2h.

[0019] As a preferred embodiment of this application, the biological pretreatment method for improving the efficiency of true protein production from wet baijiu lees is characterized in that: in step D, by weight, there are 1-5 parts of Candida utilis, 15-19 parts of water, and 880-1000 parts of wet baijiu lees after anaerobic fermentation in step C; more preferably, there are 3 parts of Candida utilis, 17 parts of water, and 980 parts of wet baijiu lees after anaerobic fermentation in step C; wherein the viable count of Candida utilis is ≥3 billion CFU / g.

[0020] As a preferred embodiment of this application, the biological pretreatment method for improving the efficiency of producing true protein from wet baijiu lees is characterized in that: in step D, the temperature of aerobic fermentation is 30±2℃ and the fermentation time is 72±2h.

[0021] The present invention also protects the baijiu lees obtained by any of the above-described biological pretreatment methods, in which the true protein content is significantly increased.

[0022] Preferably, after pretreatment using the above methods, the true protein content of the wet distillers' grains fermented feed increases by 40.55%, the neutral detergent fiber content decreases by 16.73%, and the loss during the pretreatment process is 10.62%.

[0023] The beneficial effects of this invention compared to the prior art are:

[0024] (i) In the prior art, dry liquor lees are mainly used for pretreatment, while the present invention directly uses wet liquor lees for fermentation and other pretreatment, which reduces the energy loss of drying in the traditional process of using dry liquor lees.

[0025] (II) In existing technologies, fresh baijiu lees are directly used for pretreatment such as fermentation. During the fermentation process, they are easily affected by contamination by miscellaneous bacteria, resulting in reduced nutritional quality and significant losses of the wet baijiu lees after fermentation and other pretreatment. In contrast, this invention reduces the impact of miscellaneous bacteria in the wet baijiu lees on the subsequent aerobic fermentation by first performing chemical treatment and anaerobic fermentation, thereby greatly reducing the fermentation loss rate of wet baijiu lees.

[0026] (III) In the prior art, the treatment of fibers with alkali requires high temperature. However, in this invention, an appropriate amount of urea is added during the alkali chemical treatment process, which reduces the occurrence of fiber structure damage and repolymerization after conventional alkali treatment, ultimately achieving good fiber degradation effect at room temperature. At the same time, the addition of urea during the alkali chemical treatment process also provides a nitrogen source for the subsequent aerobic fermentation and generation of true proteins.

[0027] (iv) In the existing technology of pretreatment of fermented liquor lees, although cellulase and protease are used in combination, the use of protease is aimed at increasing the small peptides of liquor lees, and the degradation of liquor lees fiber by an appropriate amount of protease has not been studied. However, the present invention improves the rate of reducing sugar production by cellulase hydrolysis by combining an appropriate amount of protease and cellulase, and also provides abundant sugar for subsequent aerobic fermentation. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0030] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this description, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0031] In this invention, some conventional operating equipment, devices and components have been omitted or only briefly described.

[0032] Unless otherwise specified in the examples, the conditions shall be performed according to the standard conditions or the conditions recommended by the manufacturer.

[0033] In this application, unless otherwise specified, % represents the percentage content by mass, i.e., wt%.

[0034] Example 1

[0035] This example illustrates the effect of chemical treatment on the fibers of wet distillers' grains.

[0036] Recorded by weight:

[0037] The blank control group consisted of untreated wet liquor lees.

[0038] Mix 1000 parts of wet white wine lees, 25 parts of calcium hydroxide, and urea evenly, then seal and place in a constant temperature environment of 30℃ for 48 hours. Add urea according to the experimental design in Table 1.

[0039] Table 1 Experimental Design

[0040]

[0041] Table 2. Effects of different ratios of calcium hydroxide and urea on the degradation of baijiu lees fiber (dry matter basis)

[0042]

[0043] Table 2 shows that, based on the chemical pretreatment of wet baijiu lees with calcium hydroxide, the effects of adding different amounts of urea on the degradation of wet baijiu lees fibers varied. Treatment group two, with 25 parts calcium hydroxide and 8.5 parts urea, showed the lowest neutral detergent fiber content, decreasing from 53.24% to 42.33% compared to the blank control group, a decrease of 10.91 percentage points. During the pretreatment process, the addition of alkali releases free hydroxide ions, disrupting the ether bonds in the lignin structure and dissociating the phenolic hydroxyl groups to form phenolic anions. This degrades the large molecular structure of lignin into relatively smaller molecular fragments, making them easier to dissolve and exposing cellulose and hemicellulose. Simultaneously, on the basis of alkali, the addition of urea allows it to adhere to the surface of the baijiu lees fiber after the alkali has disrupted the fiber molecular structure, forming inclusion complexes that prevent the repolymerization of the decomposed fibers after alkali degradation, thereby improving the degree of fiber degradation. However, in this embodiment, adding urea while keeping the amount of calcium hydroxide constant actually reduced the effect of the wet distillers' grains on the neutral detergent fiber, indicating that the optimal chemical pretreatment ratio is 1000 parts wet distillers' grains, 25 parts calcium hydroxide, and 8.5 parts urea.

[0044] Example 2

[0045] This example illustrates the effect of different amounts of protease on the pretreatment of wet distillers' grains.

[0046] Recorded by weight:

[0047] The blank control group consisted of untreated wet liquor lees.

[0048] A. Preparation of bacterial enzyme solution: 0.1 parts of *Pediococcus lactis*, 3 parts of *Candida utilis*, 2 parts of cellulase, and 33.3 parts of protease were added to each treatment group according to the proportions in Table 3, and dissolved in 34.9, 34.7, 34.5, 34.1, and 33.3 parts of water, respectively, and stirred evenly. The viable count of *Pediococcus lactis* was 10 billion CFU / g; the viable count of *Candida utilis* was 3 billion CFU / g; the cellulase activity was 50,000 U / g; and the protease activity was 10,000 U / g.

[0049] Table 3 Experimental Design

[0050]

[0051] B. Anaerobic fermentation treatment: Spray 40 parts of the bacterial enzyme solution from step A evenly onto 960 parts of wet white wine lees, mix evenly, and then seal and anaerobic ferment in a constant temperature environment of 37℃ for 72 hours.

[0052] After the samples were pretreated according to the above method, they were dried and then the neutral detergent fiber (GB / T20806-2006) and reducing sugar (DNS method) were determined.

[0053] Table 4. Effects of different protease additions on the fiber content of baijiu lees (dry matter basis)

[0054]

[0055] Table 4 shows that with the increase of protease addition during anaerobic fermentation pretreatment, the decrease in neutral detergent fiber and reducing sugar content of baijiu lees first increased and then decreased. Treatment group 2, with 0.2 parts protease, had the lowest neutral detergent fiber content and the highest reducing sugar content. Compared with untreated baijiu lees, the neutral detergent fiber content in treatment group 2 decreased from 53.24% to 41.29%, a decrease of 11.95 percentage points. Simultaneously, compared with treatment group 1 (without protease), treatment group 2 had a lower neutral detergent fiber content, indicating that the combined use of protease and cellulase can improve the cellulase's effect on fiber degradation and reducing sugar release in baijiu lees. This may be related to the fact that some protein structures in baijiu lees are encapsulated by fiber, forming fiber-insoluble proteins. Adding a suitable protease breaks down the protein-fiber encapsulation structure, thereby improving the fiber degradation effect of cellulase. However, when the amount of protease added was increased to 0.4, 0.8, and 1.6 parts, respectively, compared with the blank control group, the neutral detergent fiber content in treatment groups three, four, and five decreased by 9.03, 7.18, and 6.19 percentage points, respectively, while the reducing sugar content increased by 2.54, 1.99, and 1.70 percentage points, respectively. This indicates that excessive protease addition can affect the effect of cellulase in reducing the fiber content of distillers' grains. This may be because cellulase itself is a protein; if a high amount of protease is not completely consumed by the substrate, the remaining protease may hydrolyze the peptide bonds in the cellulase, thereby reducing the catalytic efficiency of the cellulase. Therefore, in this embodiment, the optimal amount of protease added is 0.02 parts.

[0056] Example 3

[0057] This embodiment illustrates the effect of different pretreatment processes on the fermentation of wet baijiu lees, including the following steps:

[0058] Recorded by weight:

[0059] Table 5 Experimental Design

[0060]

[0061] The blank control group consisted of a mixture of 860 samples of untreated wet baijiu lees and 100 samples of wheat bran.

[0062] The preprocessing steps for Group 1 are as follows:

[0063] A. Preparation of bacterial enzyme solution: Dissolve 0.1 parts of *Pediococcus lactis*, 3 parts of *Candida utilis*, 2 parts of cellulase, and 0.2 parts of protease in 34.7 parts of water and stir evenly. The viable count of *Pediococcus lactis* is 10 billion CFU / g; the viable count of *Candida utilis* is 3 billion CFU / g; the activity of cellulase is 50,000 U / g; and the activity of protease is 10,000 U / g.

[0064] B. Anaerobic fermentation treatment: Spray 40 parts of the bacterial enzyme solution from step A evenly onto 100 parts of wheat bran, then mix it evenly with 860 parts of wet white wine lees, and then seal and anaerobic ferment in a constant temperature environment of 37℃ for 72 hours.

[0065] The preprocessing steps for Group 2 are as follows:

[0066] A. Preparation of bacterial enzyme solution: Dissolve 0.1 parts of *Pediococcus lactis*, 3 parts of *Candida utilis*, 2 parts of cellulase, and 0.2 parts of protease in 34.7 parts of water and stir evenly. The viable count of *Pediococcus lactis* is 10 billion CFU / g; the viable count of *Candida utilis* is 3 billion CFU / g; the activity of cellulase is 50,000 U / g; and the activity of protease is 10,000 U / g.

[0067] B. Aerobic fermentation treatment: Spray 40 parts of the enzyme solution from step A evenly onto 100 parts of wheat bran, then mix it evenly with 860 parts of wet white wine lees, and then ferment it in an open aerobic environment at a constant temperature of 30℃ for 72 hours.

[0068] The preprocessing steps for Group 3 are as follows:

[0069] A. Preparation of bacterial enzyme solution: Dissolve 0.1 parts of Pediococcus lactis, 2 parts of cellulase, and 0.2 parts of protease in 17.7 parts of water and stir evenly. The viable count of Pediococcus lactis is 10 billion CFU / g; the activity of cellulase is 50,000 U / g; and the activity of protease is 10,000 U / g.

[0070] B. Anaerobic fermentation treatment: Spray 20 parts of the enzyme solution from step A evenly onto 100 parts of wheat bran, then mix it evenly with 860 parts of wet white wine lees, and then seal and anaerobic ferment in a constant temperature environment of 37℃ for 72 hours.

[0071] C. Aerobic fermentation treatment: Dissolve 3 parts of Candida utilis in 17 parts of water to form a yeast solution, and then inoculate it into 980 parts of baijiu mash treated in step B anaerobic fermentation. Ferment aerobically at 30℃ for 72 hours. The viable count of Candida utilis is 3 billion CFU / g.

[0072] The preprocessing steps for processing group four are as follows:

[0073] A. Chemical treatment: Mix 832 parts of wet white wine lees, 21 parts of calcium hydroxide and 7 parts of urea evenly, then seal and place in a constant temperature environment of 30℃ for 48 hours.

[0074] B. Preparation of bacterial enzyme solution: Dissolve 0.1 parts of Pediococcus lactis, 2 parts of cellulase, and 0.2 parts of protease in 17.7 parts of water and stir evenly. The viable count of Pediococcus lactis is 10 billion CFU / g; the activity of cellulase is 50,000 U / g; and the activity of protease is 10,000 U / g.

[0075] C. Anaerobic fermentation treatment: Spray 20 parts of the bacterial enzyme solution from step B evenly onto 100 parts of wheat bran, then mix it evenly with 860 parts of baijiu lees that have been chemically treated in step A, and seal it for anaerobic fermentation at a constant temperature of 37℃ for 72 hours.

[0076] D. Aerobic fermentation treatment: Dissolve 3 parts of Candida utilis in 17 parts of water to form a yeast solution, and then inoculate it into 980 parts of the baijiu lees after anaerobic fermentation in step C. Ferment aerobically at 30℃ for 72 hours. The viable count of Candida utilis is 3 billion CFU / g.

[0077] After pretreatment using the above method, the samples were dried and then the crude protein (GB / T 6432—2018), true protein (alkaline copper sulfate method), neutral detergent fiber (GB / T20806-2006), and pretreatment loss rate ((dry matter content before pretreatment - dry matter content after pretreatment) / dry matter content before pretreatment) were determined.

[0078] Table 6. Effects of different pretreatments on the pretreatment effect of wet baijiu lees (dry matter basis)

[0079]

[0080] Table 6 shows that different pretreatment methods resulted in different effects on wet baijiu lees. Compared with the blank control group before pretreatment, the wet baijiu lees in anaerobic fermentation pretreatment group 1 showed the highest decrease in neutral detergent fiber, but its crude protein and true protein levels hardly increased. This is mainly because Candida utilis can only perform alcohol metabolism during anaerobic fermentation and cannot undergo cell proliferation. Compared with the blank control group before pretreatment, the crude protein and true protein levels in aerobic fermentation pretreatment group 2 increased by 1.96 and 3.35 percentage points, respectively, but the loss rate during pretreatment was as high as 20.97%, causing material concentration and resulting in an increase in neutral detergent fiber instead of a decrease. A large number of miscellaneous bacteria exist in the wet baijiu lees after brewing and during transportation. During aerobic fermentation, the inoculated microorganisms and miscellaneous bacteria compete for growth, ultimately increasing the losses during fermentation pretreatment. Compared with the blank control group before pretreatment, the crude protein and true protein levels in the combined anaerobic and aerobic fermentation pretreatment group 3 increased by 3.22 and 3.49 percentage points, respectively, but the neutral detergent fiber level did not decrease significantly. Compared with the blank control group before pretreatment, the crude protein and true protein content of the pretreatment group four (combining chemical pretreatment, anaerobic fermentation, and aerobic fermentation) increased by 5.03 and 4.68 percentage points, respectively, while the neutral detergent fiber content decreased by 8.33 percentage points. This indicates that the addition of chemical pretreatment to the treatment group three improved the degradation rate of neutral detergent fiber during pretreatment, enabling *Candida utilis* to utilize more fiber to degrade sugars and generate cell protein during aerobic fermentation, and to utilize some urea to convert into organic nitrogen, ultimately improving the nutritional indicators of the wet distillers' grains pretreatment.

[0081] In summary, compared with other wet distillers' grains pretreatment methods, the technology of this invention has a higher true protein enhancement rate and lower pretreatment loss. Its production cost per unit of true protein is lower than the cost per unit of crude protein in soybean meal, which provides more options for replacing soybean meal in feed formulations.

[0082] The foregoing basic examples and their further alternative examples of the present invention can be freely combined to form multiple embodiments, all of which are embodiments that can be adopted and are claimed by the present invention. In the present invention, each alternative example can be arbitrarily combined with any other basic example and alternative example. Those skilled in the art will recognize numerous combinations.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A biological pretreatment method for improving the efficiency of true protein production from wet baijiu lees, characterized in that, Includes the following steps: A. Chemical treatment: After mixing the wet white wine lees, calcium hydroxide and urea evenly, seal and place in a constant temperature environment for chemical treatment; By weight, the wet white wine lees consist of 832 parts, calcium hydroxide 21 parts, and urea 7 parts; B. Preparation of bacterial enzyme solution: Dissolve Pyrococcus lactis, cellulase and protease in water and stir evenly to obtain bacterial enzyme solution; By weight, the composition was 0.1 parts of Pseudococcus lactis, 2 parts of cellulase, 0.2 parts of protease, and 17.7 parts of water. C. Anaerobic fermentation treatment: After the enzyme solution prepared in step B is evenly sprayed onto the bran, it is then mixed evenly with the chemically treated baijiu lees in step A, and sealed for anaerobic fermentation in a constant temperature environment of 37±2℃ for 72±2h. D. Aerobic fermentation treatment: Dissolve 1-5 parts of Candida utilis in 15-19 parts of water to form a yeast liquid, and then inoculate it into 880-1000 parts of the baijiu lees that have undergone anaerobic fermentation in step C. Then, aerobic fermentation is carried out in an open environment at 30±2℃ for 72±2h.

2. The biological pretreatment method for improving the efficiency of true protein production from wet baijiu lees according to claim 1, characterized in that: In step A, the temperature during chemical treatment is 30±2℃, and the treatment time is 48±2h.

3. The biological pretreatment method for improving the efficiency of true protein production from wet baijiu lees according to claim 1, characterized in that: In step B, the viable count of Pediococcus lactis is ≥10 billion CFU / g, the cellulase activity is ≥50,000 U / g, and the protease activity is ≥10,000 U / g.

4. The biological pretreatment method for improving the efficiency of true protein production from wet baijiu lees according to claim 1, characterized in that: In step C, by weight, the bacterial enzyme solution is 13-27 parts, the wheat bran is 50-150 parts, and the baijiu lees chemically treated in step A is 823-937 parts.

5. The biological pretreatment method for improving the efficiency of true protein production from wet baijiu lees according to claim 1, characterized in that: In step D, the viable count of Candida utilis is ≥3 billion CFU / g.

6. The liquor lees obtained by the biological pretreatment method according to any one of claims 1-5.

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