Distillers' grains recycling process

Abstract

This invention relates to a process for recycling and treating distiller's grains, comprising: pretreatment: solid-liquid separation of distiller's grains to obtain solid material and microbial-containing liquid, adjusting the carbon-to-nitrogen ratio of the solid material to 18-30:1; enzymatic hydrolysis: adding a compound enzyme preparation and an enzyme stabilizer to the solid material for enzymatic hydrolysis to obtain enzymatic hydrolysis products; microbial fermentation: adding a compound probiotic agent to the enzymatic hydrolysis products for fermentation to form fermented material, with microbial-containing liquid introduced during fermentation; grading: grading the fermented material through a vibrating screen to obtain coarse and fine particles; high-temperature treatment: subjecting the coarse particles to high-temperature steam explosion treatment; surface activation: surface modification treatment of the fine particles; secondary fermentation: mixing the high-temperature treated coarse particles with the fine particles, and adding the compound probiotic agent again for secondary fermentation to obtain fermented products; and drying and shaping. This recycling process has high processing efficiency, a shorter fermentation cycle, and higher nutritional content.

Description

Technical Field

[0001] This invention belongs to the field of fermentation technology and relates to a process for recycling and treating distiller's grains. Background Technology

[0002] Distiller's grains are solid residues produced during the brewing process, mainly composed of fiber, protein, yeast cells, and incompletely decomposed starch remaining after saccharification and fermentation of grains (such as sorghum, glutinous rice, and barley). Depending on the brewing raw materials and processes, distiller's grains can be categorized into baijiu (Chinese white liquor) grains, beer grains, huangjiu (yellow wine) grains, and rice wine grains, among which the grains from the sauce-aroma type have the highest nutritional value. The brewing process for sauce-aroma baijiu is the most complex and time-consuming of all aroma types, and its core processes directly affect the nutritional composition of the grains, giving them characteristics such as high crude protein content, easily absorbed dietary fiber, and a comprehensive and rich concentration of minerals and vitamins.

[0003] Currently, the lees of Maotai-flavor liquor can be treated by fermentation: the lees are simply composted or anaerobic fermented and then used as organic fertilizer. However, this method has a long fermentation cycle, generally requiring 30 to 60 days, and the fermentation is incomplete, resulting in low nutrient retention and low fertilizer efficiency.

[0004] In summary, existing methods for recycling and treating the lees of Maotai-flavor liquor have the characteristics of low processing efficiency, long fermentation cycle, and low retention rate of nutrients. Therefore, developing a high-efficiency, environmentally friendly recycling and treatment process that can fully retain the nutrients of Maotai-flavor liquor lees is of great practical significance. Summary of the Invention

[0005] The purpose of this invention is to provide a process for recycling and treating distiller's grains, which has high processing efficiency, a shorter fermentation cycle, and higher nutritional content.

[0006] A process for recycling and treating distiller's grains includes the following steps: Pretreatment: The lees are subjected to solid-liquid separation to obtain solid material and bacterial liquid, and the carbon-nitrogen ratio of the solid material is adjusted to 18-30:1; Enzymatic hydrolysis: A compound enzyme preparation and an enzyme stabilizer are added to the solid material to carry out enzymatic hydrolysis and obtain the enzymatic hydrolysis product; Microbial fermentation: A compound probiotic agent is added to the enzymatic hydrolysis product for fermentation to form fermented material. The bacterial-containing liquid is introduced during the fermentation process. Grading process: The fermentation material, after being dehydrated or dried to a suitable screening state, is graded by a vibrating screen to obtain coarse particles and fine particles. High-temperature treatment: The coarse-particle material is subjected to high-temperature steam explosion treatment; Surface activation: The fine particles undergo surface modification treatment. Secondary fermentation: The coarse particulate material after high-temperature treatment is mixed with the fine particulate material, and the compound probiotic agent is added again to obtain the fermentation product; Drying and shaping: The fermentation product is vacuum dried and granulated to obtain the finished product.

[0007] In some embodiments, the moisture content of the solid material is 50% to 60% during the pretreatment.

[0008] In some embodiments, the enzymatic hydrolysis temperature is 45°C to 55°C. The enzymatic hydrolysis time is 2 to 4 hours; The amount of the compound enzyme preparation added is 0.3% to 0.5% of the weight of the solid material, and the amount of the enzyme stabilizer added is 5% to 25% of the weight of the compound enzyme preparation. The compound enzyme preparation contains at least two polysaccharide-degrading enzymes and at least one protein-degrading enzyme. The enzyme stabilizers include amino acid substances, antioxidant substances, and metal ion chelating agents; The amino acid is selected from at least one of glycine, alanine, and proline, with a concentration of 0.05 wt% to 0.5 wt%; the antioxidant is selected from at least one of vitamin C, vitamin E, and glutathione, with a concentration of 0.01 wt% to 0.2 wt%; the metal ion chelating agent is selected from at least one of ethylenediaminetetraacetic acid and sodium citrate, with a concentration of 0.005 wt% to 0.1 wt%; and the volume ratio of the amino acid, the antioxidant, and the metal ion chelating agent is 1:(0.5 to 1.5):(0.2 to 0.8).

[0009] In some embodiments, the complex enzyme preparation comprises cellulase, hemicellulase, and protease in a mass ratio of 2.5–3.5:1.8–2.3:1.

[0010] In some embodiments, the compound probiotic agent comprises Bacillus subtilis, lactic acid bacteria, and yeast, wherein the live count ratio of Bacillus subtilis, lactic acid bacteria, and yeast is 4.5–5.5:2.5–3.5:2.

[0011] In some embodiments, during microbial fermentation, the amount of the compound probiotic agent added is 0.5% to 1% of the weight of the enzymatic hydrolysate, the fermentation temperature is 30°C to 35°C, and the fermentation time is 12 hours to 24 hours.

[0012] In some embodiments, during the grading process, the coarse particles have a particle size greater than 2 mm, and the fine particles have a particle size less than 2 mm.

[0013] In some embodiments, the steam pressure in the high-temperature treatment is 1.5 MPa to 2.5 MPa, and the treatment time is 3 to 5 minutes.

[0014] In some embodiments, during the surface activation, the specific surface area of ​​the fine particles is increased by 20% to 60%, the surface activation is performed using a 0.1 wt% to 0.5 wt% polysorbate-80 solution, the amount added is 0.5% to 0.8% of the weight of the fine particles, the treatment time is 8 minutes to 20 minutes, and the stirring rate is 100 rpm to 200 rpm.

[0015] In some implementation schemes, during the secondary fermentation, the fermentation temperature is 25°C to 30°C; the fermentation time is 36 hours to 48 hours; and the amount of the compound probiotic agent added is 0.2% to 0.5% of the weight of the mixture.

[0016] The lees recycling process provided in this application includes the following steps: Pretreatment: Solid-liquid separation of the lees to obtain solid material and bacterial-containing liquid, adjusting the carbon-to-nitrogen ratio of the solid material to 18-30:1; Enzymatic hydrolysis: Adding a compound enzyme preparation and an enzyme stabilizer to the solid material for enzymatic hydrolysis to obtain the hydrolysis product; Microbial fermentation: Inoculating the hydrolysis product with a compound probiotic agent for fermentation to form fermented material, introducing the bacterial-containing liquid during fermentation; Grading: Grading the fermented material through a vibrating screen to obtain coarse and fine particles; High-temperature treatment: Exposing the coarse particles to high-temperature steam explosion treatment; Surface activation: Surface modification treatment of the fine particles; Secondary fermentation: Mixing the high-temperature treated coarse and fine particles, and inoculating with a compound probiotic agent again to obtain the fermentation product; Drying and molding: Vacuum drying the fermentation product and granulating it to obtain the finished product. This recycling process has high processing efficiency, a shorter fermentation cycle, and higher nutritional content. Attached Figure Description

[0017] Figure 1 This is a flowchart of a process for recycling and treating distiller's grains according to an embodiment of this application. Detailed Implementation

[0018] The following specific embodiments further illustrate the technical solution of the present invention. These specific embodiments do not represent a limitation on the scope of protection of the present invention. Non-essential modifications and adjustments made by others based on the concept of the present invention still fall within the scope of protection of the present invention.

[0019] The lees of Maotai-flavor liquor can be treated by fermentation: the lees are simply composted or anaerobic fermented and then used as organic fertilizer. However, this method has a long fermentation cycle, generally requiring 30 to 60 days, and the fermentation is not thorough, resulting in low nutrient retention and low fertilizer efficiency.

[0020] To solve the above problems, refer to Figure 1 , Figure 1 This is a flowchart illustrating a process for recycling and treating distiller's grains according to an embodiment of this application. This application provides a process for recycling and treating distiller's grains, including the following steps: S1. Pretreatment: The lees are separated into solid and liquid components to obtain solid material and liquid containing bacteria. The carbon-nitrogen ratio of the solid material is adjusted to 18-30:1. S2. Enzymatic hydrolysis: Add compound enzyme preparation and enzyme stabilizer to solid materials to carry out enzymatic hydrolysis and obtain enzymatic hydrolysis products; S3. Microbial fermentation: A compound probiotic agent is added to the enzymatic hydrolysis product for fermentation to form fermented material. During the fermentation process, a liquid containing bacteria is introduced. S4. Grading process: The fermentation material that has been dehydrated or dried to a suitable screening state is graded by a vibrating screen to obtain coarse particles and fine particles. S5. High-temperature treatment: High-temperature steam explosion treatment is applied to coarse-particle materials. S6. Surface activation: Fine particles undergo surface modification treatment; S7. Secondary fermentation: The coarse and fine particles after high-temperature treatment are mixed and then inoculated with compound probiotics to obtain the fermentation product. S8. Drying and shaping: The fermentation product is vacuum dried and granulated to obtain the finished product.

[0021] In step S1, the distiller's grains undergo solid-liquid separation, typically using centrifugal filtration or pressure filtration to separate the distiller's grains into solid material and a microbial-containing liquid. This facilitates classification and processing of the distiller's grains, improving processing efficiency and effectiveness. The solid material in the distiller's grains includes organic matter such as crude fiber, crude protein, and starch. The carbon-to-nitrogen ratio (C / N ratio) of the solid material is adjusted to be between 18 and 30:1. Possible C / N ratios include 18:1, 19:1, 20:1, 25:1, and 30:1. A C / N ratio outside this range can easily lead to microbial metabolic imbalance. A C / N ratio within this range provides a suitable nutrient environment for microbial growth and enzymatic reactions. This can be achieved by increasing carbon sources, such as corn stalk powder, if the carbon content is insufficient; or by increasing nitrogen sources, such as soybean meal, if the nitrogen content is insufficient.

[0022] In step S2, a compound enzyme preparation and an enzyme stabilizer are added to the solid material for enzymatic hydrolysis to obtain the hydrolysis product. Enzymatic hydrolysis of solid material can destroy anti-nutritional factors in the lees and decompose difficult-to-utilize macromolecules, thereby improving the nutritional value, palatability, and utilization rate of the lees. The compound enzyme preparation can decompose structural carbohydrates and release usable nutrients. However, the activity of the compound enzyme preparation is affected by factors such as temperature, pH value, metal ions, proteases in the lees, and storage time (the lees environment is acidic / alkaline, contains trace metal ions, and the physical adsorption of solid material also reduces enzyme activity). If enzyme activity is rapidly lost, the hydrolysis effect will decrease significantly. Therefore, the role of the enzyme stabilizer is to protect the spatial structure of the enzyme preparation, inhibit enzyme activity degradation, and ensure that the enzyme functions stably throughout the entire lees processing (enzymatic reaction, storage, and transportation).

[0023] In step S3, a compound probiotic agent is added to the enzymatic hydrolysate for fermentation, forming fermented material. The compound probiotic agent allows beneficial microorganisms to quickly become the dominant flora in the material, controlling the fermentation process, preventing contamination by other microorganisms, and ensuring controllable fermentation direction. Simultaneously, through the metabolic action of the probiotics, the nutritional quality of the enzymatically hydrolyzed distillers' grains is improved, anti-nutritional factors are deeply degraded, palatability is optimized, and storage properties are enhanced, ultimately transforming the enzymatically hydrolyzed distillers' grains into high-quality fermented feed containing active probiotics. During fermentation, a microbial liquid containing brewer's yeast and lactic acid bacteria is introduced. Both brewer's yeast and lactic acid bacteria are probiotics. The addition of this microbial liquid provides more probiotics to the enzymatic hydrolysate, improving fermentation efficiency and preventing waste of the microbial liquid.

[0024] In step S4, the fermentation material that has been dehydrated or dried to a suitable screening state is classified by a vibrating screen to obtain coarse and fine particles. Different treatments can be carried out for different particle sizes to improve the treatment effect.

[0025] In step S5, the coarse particles are subjected to high-temperature steam explosion treatment, which breaks down the dense fiber structure through physical explosion, while further optimizing the physical properties and nutrient utilization efficiency of the coarse particles, thereby improving the treatment effect and efficiency.

[0026] In step S6, the fine particles undergo surface modification treatment to increase their surface area, which can amplify the inherent advantages of fine particles being "small in size and easy to mix". By increasing the specific surface area, a triple upgrade is achieved in terms of nutrient adsorption, digestibility, and processing adaptability.

[0027] In step S7, the high-temperature treated coarse-particle material is mixed with the fine-particle material, and then a compound probiotic agent is added again to obtain the fermentation product. By separately treating the coarse and fine particles and then carrying out secondary fermentation, the fermentation effect of the distiller's grains can be further improved.

[0028] In step S8, the fermentation product is vacuum dried and granulated to obtain the finished product for easy storage and transportation.

[0029] The processing cycle of the distiller's grains recycling process in this application is between 50 and 70 hours, which is significantly shorter than the 30 to 60 days required for traditional composting. Furthermore, the fermentation effect of this application is superior to that of traditional composting.

[0030] In some optional embodiments, the moisture content of the solid material is 50%–60% during pretreatment. The moisture content of the solid material can be any amount, such as 50%, 53%, 55%, 57%, or 60%, and this application does not impose any restrictions. When the moisture content of the solid material is below 50%, there is insufficient free water to form an aqueous phase. Enzyme molecules are adsorbed onto the surface of the solid fibers and cannot move, resulting in insufficient contact with the substrate. This leads to a decrease in enzymatic hydrolysis efficiency of over 60%, and may even result in "enzymatic stagnation." When the moisture content of the solid material is above 60%, while enzymatic hydrolysis efficiency can be guaranteed, the excessive water phase can easily create an overly anaerobic environment during subsequent fermentation, leading to spoilage. Simultaneously, the enzymatic hydrolysis products are easily lost with the excess water, resulting in nutrient waste. A moisture content of 50%–60% in the solid material allows the interstices of the distillers' grains to be filled with bound water plus a small amount of free water, providing a sufficient aqueous reaction phase for enzymatic hydrolysis and ensuring sufficient contact between enzyme molecules and the substrate, thus guaranteeing the efficient decomposition of macromolecules such as cellulose and starch.

[0031] In some optional embodiments, the enzymatic hydrolysis temperature is 45℃~55℃. The enzymatic hydrolysis temperature can be 45℃, 47℃, 50℃, 52℃, 55℃, etc. This application does not impose any restrictions. When the enzymatic hydrolysis temperature is less than 45℃, the enzyme activity is insufficient, the enzymatic hydrolysis efficiency is low, the cycle is long, and the nutrient release is insufficient. When the enzymatic hydrolysis temperature is greater than 55℃, the enzyme molecules denature and become inactive, the enzymatic hydrolysis stops directly, is irreversible, and affects the subsequent entire process.

[0032] In some optional embodiments, the enzymatic hydrolysis time is 2 to 4 hours. The enzymatic hydrolysis time can be 2 hours, 3 hours or 4 hours. This application does not limit it. When the enzymatic hydrolysis time is less than 2 hours, the enzymatic hydrolysis is insufficient, the core macromolecules are not decomposed, and the release of nutrients is incomplete. When the enzymatic hydrolysis time is greater than 4 hours, the enzymatic hydrolysis is excessive and causes negative effects, such as nutrient waste, the growth of miscellaneous bacteria and reduced efficiency.

[0033] In some optional embodiments, the amount of compound enzyme preparation added is 0.3% to 0.5% of the weight of solid material, and the amount of enzyme stabilizer added is 5% to 25% of the weight of compound enzyme preparation. The amount of compound enzyme preparation added can be 0.3%, 0.4%, or 0.5% of the weight of solid material, and this application does not impose any restrictions. If it is less than 0.3%, the number of enzyme molecules is insufficient, and saturated enzymatic hydrolysis cannot be completed within 2 to 4 hours, resulting in insufficient decomposition of large molecules in the lees. If it is more than 0.5%, the enzyme preparation is excessive, most enzyme molecules are wasted without participating in catalysis, and subsequent excessive decomposition of small molecule nutrients due to enzymatic hydrolysis will be counterproductive, leading to a significant increase in production costs. The amount of enzyme stabilizer added is 5%, 10%, 15%, 20%, or 25% of the weight of compound enzyme preparation, and this application does not impose any restrictions. If it is less than 5%, the stabilizer is insufficient and cannot offset physical adsorption, resulting in low enzyme utilization. If it is more than 25%, the stabilizer is excessive, forming an excessively thick protective film on the surface of enzyme molecules, hindering contact between enzyme molecules and substrates, thus reducing catalytic efficiency and wasting stabilizer.

[0034] In some optional embodiments, the complex enzyme preparation comprises at least two polysaccharide-degrading enzymes and at least one proteolytic enzyme. The polysaccharide-degrading enzymes may be two or more selected from cellulase, α-amylase + saccharifying enzyme (compound system), and hemicellulase. The complex enzyme preparation comprises cellulase, hemicellulase, and protease in a mass ratio of 2.5–3.5:1.8–2.3:1, where the ratio may be 2.5:1.8:1, 3:2:1, 3.5:2.3:1, etc. In one example, the complex enzyme preparation comprises cellulase, hemicellulase, and protease in a mass ratio of 3:2:1. The proteolytic enzyme may be any one of pectinase, β-glucanase, or mannanase.

[0035] In some optional embodiments, the enzyme stabilizer includes amino acid substances, antioxidant substances, and metal ion chelating agents. The amino acid substances are selected from at least one of glycine, alanine, and proline, and the concentration is 0.05wt% to 0.5wt%. The concentration can be 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, or 0.5wt%, and this application does not impose any restrictions. When the concentration is below 0.05wt%, an effective hydrophilic protective film cannot be formed, the enzyme molecules are easily adsorbed by the solids of distiller's grains, the conformation is easily changed, the activity retention rate drops significantly, and the enzymatic hydrolysis efficiency decreases. When the concentration is above 0.5wt%, the high concentration of amino acids in the system creates high osmotic pressure, causing the enzyme molecules to lose water and denature. At the same time, excessive amino acids will compete with the enzyme substrate for binding sites, reducing the enzyme catalytic efficiency.

[0036] The antioxidant is selected from at least one of vitamin C, vitamin E, and glutathione, with a concentration of 0.01wt% to 0.2wt%. The concentration can be 0.01wt%, 0.05wt%, 0.1wt%, or 0.2wt%, and this application does not impose any restrictions. When the concentration is below 0.01wt%, it cannot effectively remove free radicals in the enzymatic hydrolysis system, and the polypeptide chains of the enzyme molecules are easily oxidized and broken, causing irreversible inactivation of the enzyme. When the concentration is above 0.2wt%, excessive amounts will produce reduction side reactions, destroying small molecule nutrients (such as monosaccharides and small peptides) in the enzymatic hydrolysis system. In addition, some synthetic antioxidants will slightly inhibit enzyme activity and increase production costs.

[0037] The metal ion chelating agent is selected from at least one of ethylenediaminetetraacetic acid (EDTA) and sodium citrate, with a concentration of 0.005 wt% to 0.1 wt%. The concentration can be 0.005 wt%, 0.01 wt%, 0.005 wt%, or 0.1 wt%, etc., and this application does not impose any limitation. When the concentration is below 0.005 wt%, it cannot completely complex the heavy metal ions in the distillers' grains. The ions will occupy the enzyme's active site, destroy the enzyme's spatial structure, and inhibit the enzyme's catalytic activity. When the concentration is above 0.1 wt%, it will complex the necessary metal ions (such as magnesium and zinc ions) required for the enzyme molecule to exert its activity, leading to the destruction of the enzyme's active site structure and the loss of the enzyme's catalytic ability. Simultaneously, the chelating agent easily binds to minerals in the distillers' grains, reducing the utilization rate of feed minerals.

[0038] The volume ratio of amino acids, antioxidants, and metal ion chelators is 1:(0.5-1.5):(0.2-0.8), and the ratio can be 1:0.5:0.2, 1:0.8:0.4, 1:1:0.5, 1:1.2:0.6, 1:1.5:0.8, etc., which are not limited in this application. When the ratio is below the lower limit, the antioxidant and ion complexation protection are insufficient, the enzyme molecules are easily oxidized and inactivated, the active sites are destroyed by heavy metal ions, the catalytic efficiency drops sharply, the overall protective effect of the stabilizer is lost by more than 80%, and the utilization rate of the compound enzyme is greatly reduced. When the ratio is above the upper limit, the excessive antioxidant will cause reduction side reactions that destroy nutrients, inhibit enzyme activity, and interfere with subsequent probiotic fermentation; the excessive chelator will complex the metal ions necessary for enzyme activity, causing the enzyme to be completely inactivated, and at the same time, it will bind to the feed minerals and reduce their utilization rate; the excessive components will damage the amino acid protective film, aggravate the adsorption and loss of enzyme molecules, and have multiple side effects.

[0039] In some optional embodiments, the compound probiotic agent comprises Bacillus subtilis, lactic acid bacteria, and yeast, with a live count ratio of 4.5–5.5:2.5–3.5:2. The live count ratio of Bacillus subtilis, lactic acid bacteria, and yeast can be 4.5:2.5:2, 5:3:2, or 5.5:3.5:2.

[0040] When the ratio is below 5.5:3.5:2, the core functions of the microbial community are lost. Insufficient Bacillus subtilis results in weak fiber degradation and antibacterial ability, making the material susceptible to contamination by other microorganisms. Insufficient lactic acid bacteria lead to slow acid production, ineffective pH regulation, and easy spoilage during fermentation. Insufficient yeast results in poor nutrient conversion and flavor improvement, insufficient protein enhancement, and low palatability, leading to a significant decline in overall fermentation efficiency and the quality of the distiller's grains. When the ratio is above 4.5:2.5:2, the microbial communities inhibit each other, and the synergistic system collapses. Excessive Bacillus subtilis consumes substrate and inhibits the proliferation of other bacteria. Excessive lactic acid bacteria cause a sharp drop in pH, inhibiting yeast metabolism and making the distiller's grains overly acidic. Excessive yeast competes for nutrients, delaying acid reduction, increasing the risk of contamination, and resulting in excessively high alcohol content in the distiller's grains. All of these factors disrupt the fermentation process, leading to nutritional imbalance, poor palatability, and reduced feeding value in the distiller's grains.

[0041] In some optional embodiments, the amount of compound probiotic agent added is 0.5% to 1% of the weight of the enzymatic hydrolysis product. The amount of compound probiotic agent added is 0.5%, 0.7% or 1% of the weight of the enzymatic hydrolysis product, etc. This application does not impose any restrictions. When the amount added is less than 0.5%, the total number of live bacteria is insufficient, and it is impossible to quickly form a dominant bacterial group. The antibacterial and antifouling ability is weak, and it is easy to breed miscellaneous bacteria, leading to fermentation and spoilage. The core functions of each strain (fiber reduction, acid production, and nutrient conversion) are not fully exerted. The effects of crude fiber degradation, protein enhancement and flavor improvement of the lees are extremely poor. The nutrient release after fermentation is insufficient, the palatability is poor, and there is no quality improvement effect in subsequent livestock and poultry feeding. When the addition amount is higher than 1%, the excessive amount of live bacteria will cause competition among the strains for the limited nutrient substrate in the lees, breaking the 5:3:2 synergistic ratio of the microbial community and causing mutual inhibition. At the same time, it will increase the fermentation cost, and the metabolic products of the excessive microbial community (such as lactic acid and alcohol) will accumulate, resulting in excessive acidity / alcohol content in the lees, significantly reducing palatability, and may also reduce the overall nutritional value of the lees due to excessive nutrient consumption.

[0042] In some optional embodiments, the fermentation temperature is 30℃~35℃, and the fermentation temperature can be 30℃, 32℃, 35℃, etc., which are not limited in this application. The fermentation time is 12 hours~24 hours, and the fermentation time can be 12 hours, 15 hours, 17 hours, 20 hours, etc., which are not limited in this application.

[0043] In some alternative embodiments, during the grading process, the coarse particles have a diameter greater than 2 mm, and the fine particles have a diameter less than 2 mm.

[0044] In some optional embodiments, during high-temperature treatment, the steam pressure is 1.5 MPa to 2.5 MPa, and the treatment time is 3 to 5 minutes. The steam pressure can be 1.5 MPa, 1.8 MPa, 2 MPa, 2.3 MPa, or 2.5 MPa, etc., and this application does not impose any limitations. The treatment time can be 3 minutes, 4 minutes, or 5 minutes, etc., and this application does not impose any limitations. When the steam pressure is less than 1.5 MPa or the treatment time is less than 3 minutes, the steam cannot fully penetrate the dense fiber structure of the coarse particles, resulting in insufficient bursting force. The fiber bundles are difficult to tear effectively, the coarse fibers are not completely degraded, the nutrient coating layer is not opened, and the coarse particles still have a hard core. The contact area during digestion by livestock and poultry is small, the rumen degradation rate and overall digestibility are significantly reduced, and the quality-improving effect of steam bursting is basically lost. Furthermore, the high-temperature antibacterial effect is insufficient; residual mold, E. coli, and other bacteria in the coarse particles are not completely killed, making them prone to mold and spoilage during subsequent storage, which also increases the safety risks for livestock and poultry feeding. When the steam pressure exceeds 2.5 MPa or the processing time exceeds 5 minutes, excessive explosion will occur, and the coarse fibrous structure will be completely destroyed into fine powder, losing the appropriate physical satiety. At the same time, high temperature and high pressure will destroy the heat-sensitive nutrients in the lees (such as vitamins, small peptides, and probiotic metabolites), and will also trigger the Maillard reaction, causing amino acids to bind and be lost with reducing sugars, reducing the utilization rate of protein and minerals in the lees.

[0045] In some optional embodiments, during surface activation, the specific surface area of ​​the fine particles increases by 20% to 60%. Surface activation uses a 0.1 wt% to 0.5 wt% polysorbate-80 solution, with the added amount accounting for 0.5% to 0.8% of the weight of the fine particles. The treatment time is 8 to 20 minutes, and the stirring rate is 100 to 200 rpm. The treatment time can be 8 minutes, 10 minutes, 15 minutes, or 20 minutes, etc., which is not limited in this application. The stirring rate can be 100 rpm, 120 rpm, 150 rpm, 180 rpm, or 200 rpm, etc., which is not limited in this application.

[0046] In some optional embodiments, during secondary fermentation, the fermentation temperature is 25℃~30℃; the fermentation time is 36 hours~48 hours; and the amount of compound probiotic agent added is 0.2%~0.5% of the weight of the mixture. The fermentation temperature can be 25℃, 28℃, 30℃, etc., and this application is not limited thereto; the fermentation time is 36 hours~48 hours, and the fermentation time can be 36 hours, 40 hours, 45 hours, or 48 hours, etc., and this application is not limited thereto; the amount of compound probiotic agent added is 0.2%~0.5% of the weight of the mixture, and can be 0.2%, 0.3%, 0.4%, or 0.5%, and this application is not limited thereto.

[0047] Example This invention comprises three embodiments (Embodiments 1, 2, and 3), corresponding to the lower limit, intermediate value, and upper limit of the key process parameter range in the claims, respectively. This design aims to strictly adhere to the patent law's requirements of "sufficient disclosure" and "support of claims": by providing endpoint embodiments, it confirms that the entire claimed parameter range is feasible and can achieve the purpose of the invention; by providing intermediate point embodiments, it further demonstrates the continuity of the technical effect within the stated range and the existence of a preferred interval, thereby proving that the scope encompassed by the claims is experimentally verified, reasonable, and not arbitrarily defined. These embodiments collectively constitute an experimental evidence system supporting the completeness and validity of the scope of protection of this invention.

[0048] Example 1 S1. Pretreatment: The lees are separated into solid and liquid components to obtain solid material and liquid containing bacteria. The water content of the separated solid material is 50%, and the carbon-nitrogen ratio of the solid material is adjusted to 18:1. S2. Enzymatic hydrolysis: A compound enzyme preparation and an enzyme stabilizer are added to the solid material for enzymatic hydrolysis at a temperature of 45°C for 2 hours. The amount of the compound enzyme preparation added is 0.3% of the weight of the solid material, and the amount of the enzyme stabilizer added is 5% of the weight of the compound enzyme preparation. The compound enzyme preparation includes cellulase, hemicellulase, and protease in a mass ratio of 2.5:1.8:1. The enzyme stabilizer includes amino acids, antioxidants, and metal ion chelators. The amino acid is selected from glycine at a concentration of 0.05 wt%. The antioxidant is selected from vitamin C at a concentration of 0.01 wt%. The metal ion chelator is selected from ethylenediaminetetraacetic acid at a concentration of 0.005 wt%. The volume ratio of the amino acid, antioxidant, and metal ion chelator is 1:0.5:0.2, yielding the enzymatic hydrolysis product. S3. Microbial fermentation: A compound probiotic agent is added to the enzymatic hydrolysis product for fermentation to form fermented material. During the fermentation process, a liquid containing bacteria is introduced. The compound probiotic agent contains Bacillus subtilis, lactic acid bacteria, and yeast. The ratio of live bacteria of Bacillus subtilis, lactic acid bacteria, and yeast is 4.5:2.5:2. The amount of compound probiotic agent added is 0.5% of the weight of the enzymatic hydrolysis product. The fermentation temperature is 30℃ and the fermentation time is 12 hours. S4. Grading process: The fermentation material is graded by a vibrating screen to obtain coarse particles and fine particles. The coarse particles are larger than 2mm and the fine particles are smaller than 2mm. S5. High-temperature treatment: The coarse-particle material is subjected to high-temperature steam explosion treatment. In the high-temperature treatment, the steam pressure is 1.5MPa and the treatment time is 3 minutes. S6. Surface Activation: The fine particles undergo surface modification treatment, increasing their specific surface area by 20%. Surface activation uses 0.1 wt% polysorbate-80, accounting for 0.5% of the weight of the fine particles. The treatment time is 8 minutes, and the stirring speed is 100 rpm. S7. Secondary Fermentation: The coarse-particle material treated at high temperature is mixed with the fine-particle material, and a compound probiotic agent is added again to obtain the fermentation product. The fermentation temperature is 25℃; the fermentation time is 36 hours; the amount of compound probiotic agent added is 0.2% of the weight of the mixture. S8. Drying and shaping: The fermentation product is vacuum dried and granulated to obtain the finished product.

[0049] Example 2 S1. Pretreatment: The lees are separated into solid and liquid components to obtain solid material and liquid containing bacteria. The water content of the separated solid material is 55%, and the carbon-nitrogen ratio of the solid material is adjusted to 25:1. S2. Enzymatic hydrolysis: A compound enzyme preparation and an enzyme stabilizer are added to the solid material for enzymatic hydrolysis at a temperature of 50°C for 3 hours. The amount of the compound enzyme preparation added is 0.4% of the weight of the solid material, and the amount of the enzyme stabilizer added is 15% of the weight of the compound enzyme preparation. The compound enzyme preparation includes cellulase, hemicellulase, and protease in a mass ratio of 3:2:1. The enzyme stabilizer includes amino acids, antioxidants, and metal ion chelators. The amino acid is selected from alanine at a concentration of 0.3 wt%. The antioxidant is selected from vitamin E at a concentration of 0.1 wt%. The metal ion chelator is selected from sodium citrate at a concentration of 0.05 wt%. The volume ratio of the amino acid, antioxidant, and metal ion chelator is 1:1:0.6, yielding the enzymatic hydrolysis product. S3. Microbial fermentation: A compound probiotic agent is added to the enzymatic hydrolysis product for fermentation to form fermented material. During the fermentation process, a liquid containing bacteria is introduced. The compound probiotic agent contains Bacillus subtilis, lactic acid bacteria, and yeast. The ratio of live bacteria of Bacillus subtilis, lactic acid bacteria, and yeast is 5:3:2. The amount of compound probiotic agent added is 0.7% of the weight of the enzymatic hydrolysis product. The fermentation temperature is 32℃ and the fermentation time is 18 hours. S4. Grading process: The fermentation material is graded by a vibrating screen to obtain coarse particles and fine particles. The coarse particles are larger than 2mm and the fine particles are smaller than 2mm. S5. High-temperature treatment: The coarse-particle material is subjected to high-temperature steam explosion treatment. In the high-temperature treatment, the steam pressure is 2MPa and the treatment time is 4 minutes. S6. Surface Activation: The fine particles undergo surface modification treatment, increasing their specific surface area by 40%. Surface activation is achieved using 0.3 wt% polysorbate-80, accounting for 0.6% of the weight of the fine particles. The treatment time is 15 minutes, and the stirring speed is 150 rpm. S7. Secondary Fermentation: The coarse-particle material treated at high temperature is mixed with the fine-particle material, and a compound probiotic agent is added again to obtain the fermentation product. The fermentation temperature is 28℃; the fermentation time is 40 hours; the amount of compound probiotic agent added is 0.3% of the weight of the mixture. S8. Drying and shaping: The fermentation product is vacuum dried and granulated to obtain the finished product.

[0050] Example 3 S1. Pretreatment: The lees are separated into solid and liquid components to obtain solid material and liquid containing bacteria. The water content of the separated solid material is 60%, and the carbon-nitrogen ratio of the solid material is adjusted to 30:1. S2. Enzymatic hydrolysis: A compound enzyme preparation and an enzyme stabilizer are added to the solid material for enzymatic hydrolysis at a temperature of 55°C for 4 hours. The amount of the compound enzyme preparation added is 0.5% of the weight of the solid material, and the amount of the enzyme stabilizer added is 25% of the weight of the compound enzyme preparation. The compound enzyme preparation includes cellulase, hemicellulase, and protease in a mass ratio of 3.5:2.3:1. The enzyme stabilizer includes amino acids, antioxidants, and metal ion chelators. The amino acid is proline at a concentration of 0.5 wt%. The antioxidant is glutathione at a concentration of 0.2 wt%. The metal ion chelator is ethylenediaminetetraacetic acid at a concentration of 0.1 wt%. The volume ratio of the amino acid, antioxidant, and metal ion chelator is 1:1.5:0.8, yielding the enzymatic hydrolysis product. S3. Microbial fermentation: A compound probiotic agent is added to the enzymatic hydrolysis product for fermentation to form fermented material. During the fermentation process, a liquid containing bacteria is introduced. The compound probiotic agent contains Bacillus subtilis, lactic acid bacteria, and yeast. The ratio of live bacteria of Bacillus subtilis, lactic acid bacteria, and yeast is 5.5:3.5:2. The amount of compound probiotic agent added is 1% of the weight of the enzymatic hydrolysis product. The fermentation temperature is 35℃ and the fermentation time is 24 hours. S4. Grading process: The fermentation material is graded by a vibrating screen to obtain coarse particles and fine particles. The coarse particles are larger than 2mm and the fine particles are smaller than 2mm. S5. High-temperature treatment: The coarse-particle material is subjected to high-temperature steam explosion treatment. In the high-temperature treatment, the steam pressure is 2.5MPa and the treatment time is 5 minutes. S6. Surface activation: The fine particles undergo surface modification treatment, increasing the specific surface area of ​​the fine particles by 20%. Surface activation is performed using 0.5wt% polysorbate-80, with the addition amount accounting for 0.8% of the weight of the fine particles. The treatment time is 20 minutes, and the stirring speed is 200 rpm. S7. Secondary Fermentation: The coarse-particle material treated at high temperature is mixed with the fine-particle material, and a compound probiotic agent is added again to obtain the fermentation product. The fermentation temperature is 30℃; the fermentation time is 48 hours; the amount of compound probiotic agent added is 0.5% of the weight of the mixture. S8. Drying and shaping: The fermentation product is vacuum dried and granulated to obtain the finished product.

[0051] Comparative Example Comparative Example 1 The difference in Example 2 is that no carbon and nitrogen adjustment is performed in step S1, i.e., the pretreatment stage.

[0052] Comparative Example 2 and Unlike Example 2, the enzymatic hydrolysis in step S2 is not followed by the microbial fermentation step S3, and the hydrolysis product directly enters the subsequent steps.

[0053] Comparative Example 3 Unlike Example 2, steps S5 and S6 are not performed after the grading process, i.e., high-temperature treatment and surface activation treatment are not performed.

[0054] Comparative Example 4 Unlike Example 2, in step S3, the bacterial liquid is not used during the microbial fermentation process; instead, an equal amount of clean water is used.

[0055] Example of effect Detection indicators and methods: (1) Enzymatic hydrolysis efficiency: reducing sugar content after enzymatic hydrolysis (DNS method), cellulose degradation rate (gravimetric method); (2) Fermentation efficiency: total number of probiotics after primary fermentation (plate count method), short-chain fatty acids (SCFA, gas chromatography) after secondary fermentation. (3) Product quality: crude protein retention rate (Kjeldahl nitrogen determination method), survival rate of active probiotics (counting after low temperature drying), and slow release period of organic fertilizer nutrients (leaching test). (4) Economic indicators: energy consumption per unit product (kWh / kg), processing cycle (h).

[0056] (1) Synergistic effect of pretreatment and enzymatic hydrolysis (comparative example 1 to the examples): The reducing sugar content of Example 1 (3.8%), Example 2 (4.5%), and Example 3 (4.0%) was significantly higher than that of CK1 (1.2%) without C / N ratio adjustment. The cellulose degradation rates of Examples 1, 2, and 3 (45.8% for Example 1, 52.0% for Example 2, and 48.2% for Example 3) were significantly higher than those of Comparative Example 1 (5.3%). This is because adjusting the C / N ratio to 18–30:1 resulted in a more suitable nutrient profile for the enzymatic hydrolysis system, activated the activity of the complex enzyme (reduced Km value), and optimized the enzymatic hydrolysis pH with organic acids in the bacterial liquid. This demonstrates that the synergistic effect of pretreatment and enzymatic hydrolysis can significantly improve substrate degradation efficiency.

[0057] (2) Synergistic effect of enzymatic hydrolysis and primary fermentation (comparative example 2 to the example): Comparative Example 2, lacking primary fermentation, saw its enzymatic hydrolysis products directly enter subsequent steps, resulting in a lower SCFA content (8.5 mg / g) in secondary fermentation compared to Examples 1 (18.6 mg / g), 2 (22.5 mg / g), and 3 (19.8 mg / g). In Examples 1-3, the small-molecule sugars produced by enzymatic hydrolysis provided a readily available carbon source for probiotics, leading to a higher number of probiotics in primary fermentation compared to Example 1 (3.5 × 10⁻⁶). 8 CFU / g), Example 2 (4.2×10 8 CFU / g), Example 3 (3.8×10 8 The microbial community metabolism is enhanced, thereby increasing the synthesis of functional substances in secondary fermentation, thus verifying the mutual promotion mechanism of enzymatic hydrolysis and fermentation.

[0058] (3) Synergistic effect of graded treatment and secondary fermentation (comparative example 3 compared with the example): In Comparative Example 3, due to the lack of coarse particle blasting and fine particle activation, the probiotic survival rate (48.6%) was significantly lower than that in Example 1 (91.2%), Example 2 (95.0%), and Example 3 (90.5%). The nutrient slow-release period (28 days) was also lower than that in Example 1 (65 days), Example 2 (75 days), and Example 3 (68 days). This is because the "porous coarse particle reservoir + highly active fine particle carrier" structure in the examples provides protection for the bacterial community, reduces drying stress, and the porous structure delays nutrient release, demonstrating the complementary advantages of structure and function.

[0059] (4) Synergistic effect of bacterial liquid reuse (Comparative Example 4 and Example): The unit energy consumption of Example 1 (0.7 kWh / kg), Example 2 (0.6 kWh / kg), and Example 3 (0.8 kWh / kg) were all lower than that of Comparative Example 4 (1.1 kWh / kg). The treatment cycle of Example 1 (60 h), Example 2 (55 h), and Example 3 (62 h) was shorter than that of Comparative Example 4 (72 h). Because the natural microbial community and metabolites in the bacterial liquid reduce the need for exogenous reagents and promote enzymatic hydrolysis and fermentation efficiency, it is demonstrated that resource recycling can reduce costs and increase efficiency.

[0060] Examples 1, 2, and 3 were conducted using the lower limit, median, and upper limit of the process parameters within the range of this invention, respectively. A comparison of the results shows that: Key performance indicators: The three examples significantly outperformed all comparative examples in key indicators such as reducing sugar content (3.8%, 4.5%, 4.0%), cellulose degradation rate (45.8%, 52.0%, 48.2%), and crude protein retention rate (88.7%, 92.5%, 89.2%). This firstly demonstrates that implementing this process within the parameter range defined in the claims can achieve treatment results far superior to traditional methods.

[0061] Further analysis showed that Example 2, which used the median parameters, achieved the best or near-best results in most of the aforementioned indicators (e.g., highest reducing sugar content of 4.5%, highest crude protein retention of 92.5%, shortest treatment cycle of 55 hours, and lowest energy consumption of 0.6 kWh / kg). This indicates that the optimal range for achieving the best balance between efficiency and effectiveness may be the parameter combination closer to the center, rather than the parameter range boundaries (e.g., C / N ratio of 20:1, enzymatic hydrolysis temperature of 50°C).

[0062] Conclusion: The data from the three embodiments collectively validate the effectiveness and rationality of the process parameter ranges (such as carbon-nitrogen ratio of 18–30:1, enzymatic hydrolysis temperature of 45–55°C, etc.) in the claims. Implementing the process within these ranges achieves the inventive objectives, while the data from Example 2 further suggests potential parameter orientations for achieving even better overall benefits.

[0063] Method Validation It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A process for recycling and treating distiller's grains, characterized in that, Includes the following steps: Pretreatment: The lees are subjected to solid-liquid separation to obtain solid material and bacterial liquid, and the carbon-nitrogen ratio of the solid material is adjusted to 18-30:1; Enzymatic hydrolysis: A compound enzyme preparation and an enzyme stabilizer are added to the solid material to carry out enzymatic hydrolysis and obtain the enzymatic hydrolysis product; Microbial fermentation: A compound probiotic agent is added to the enzymatic hydrolysis product for fermentation to form fermented material. The bacterial-containing liquid is introduced during the fermentation process. Grading process: The fermentation material, after being dehydrated or dried to a suitable screening state, is graded by a vibrating screen to obtain coarse particles and fine particles. High-temperature treatment: The coarse-particle material is subjected to high-temperature steam explosion treatment; Surface activation: The fine particles undergo surface modification treatment. Secondary fermentation: The coarse particulate material after high-temperature treatment is mixed with the fine particulate material, and the compound probiotic agent is added again to obtain the fermentation product; Drying and shaping: The fermentation product is vacuum dried and granulated to obtain the finished product.

2. The process for recycling and treating distiller's grains as described in claim 1, characterized in that, In the pretreatment, the solid material has a moisture content of 50% to 60%.

3. The process for recycling and treating distiller's grains as described in claim 1, characterized in that, In the enzymatic hydrolysis treatment, the enzymatic hydrolysis temperature is 45℃~55℃; The enzymatic hydrolysis time is 2 to 4 hours; The amount of the compound enzyme preparation added is 0.3% to 0.5% of the weight of the solid material, and the amount of the enzyme stabilizer added is 5% to 25% of the weight of the compound enzyme preparation. The compound enzyme preparation contains at least two polysaccharide-degrading enzymes and at least one protein-degrading enzyme. The enzyme stabilizers include amino acid substances, antioxidant substances, and metal ion chelating agents; The amino acid is selected from at least one of glycine, alanine, and proline, with a concentration of 0.05 wt% to 0.5 wt%; the antioxidant is selected from at least one of vitamin C, vitamin E, and glutathione, with a concentration of 0.01 wt% to 0.2 wt%; the metal ion chelating agent is selected from at least one of ethylenediaminetetraacetic acid and sodium citrate, with a concentration of 0.005 wt% to 0.1 wt%; and the volume ratio of the amino acid, the antioxidant, and the metal ion chelating agent is 1:(0.5 to 1.5):(0.2 to 0.8).

4. The process for recycling and treating distiller's grains as described in claim 3, characterized in that, The compound enzyme preparation comprises cellulase, hemicellulase, and protease in a mass ratio of 2.5–3.5:1.8–2.3:

1.

5. The process for recycling and treating distiller's grains as described in claim 1, characterized in that, The compound probiotic agent contains Bacillus subtilis, lactic acid bacteria and yeast, and the ratio of live bacteria of Bacillus subtilis, lactic acid bacteria and yeast is 4.5-5.5:2.5-3.5:

2.

6. The process for recycling and treating distiller's grains as described in claim 5, characterized in that, In microbial fermentation, the amount of the compound probiotic agent added is 0.5% to 1% of the weight of the enzymatic hydrolysis product, the fermentation temperature is 30℃ to 35℃, and the fermentation time is 12 hours to 24 hours.

7. The process for recycling and treating distiller's grains as described in claim 1, characterized in that, In the grading process, the coarse particles have a particle size greater than 2 mm, and the fine particles have a particle size less than 2 mm.

8. The process for recycling and treating distiller's grains as described in claim 1, characterized in that, In the high-temperature treatment, the steam pressure is 1.5 MPa to 2.5 MPa, and the treatment time is 3 to 5 minutes.

9. The process for recycling and treating distiller's grains as described in claim 1, characterized in that, In the surface activation, the specific surface area of ​​the fine particles increases by 20% to 60%. The surface activation uses a 0.1 wt% to 0.5 wt% polysorbate-80 solution, with the amount added accounting for 0.5% to 0.8% of the weight of the fine particles. The treatment time is 8 minutes to 20 minutes, and the stirring rate is 100 rpm to 200 rpm.

10. The process for recycling and treating distiller's grains as described in claim 5, characterized in that, In the secondary fermentation, the fermentation temperature is 25℃~30℃; the fermentation time is 36 hours~48 hours; and the amount of the compound probiotic agent added is 0.2%~0.5% of the weight of the mixture.

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