Preparation method of synthetic biological fermentation material and application of synthetic biological fermentation material in bamboo grain substitutes

Abstract

The application belongs to the field of microbial fermentation and animal nutrition engineering, and discloses a preparation method of a synthetic biological fermentation masterbatch and application of the masterbatch in bamboo grain substitutes. The fermentation masterbatch takes bamboo powder as a main carbon source, is treated through a "directional structure modification + microcapsule coating" strategy, and forms a functional fermentation particle with a core-shell structure. A fermentation system adopts Yarrowia lipolytica, Aspergillus niger, Lactobacillus brevis and Saccharomyces rouxii, realizes the synergistic enrichment of amino acids, polypeptides and short-chain fatty acids through dynamic carbon-nitrogen ratio regulation, and in-situ synthesizes growth-promoting and anti-stress metabolites in the system. After the obtained masterbatch is coated by chitosan-sodium alginate double-layer compounding, directional release can be realized in the small intestine and caecum part, the stability and bioavailability of the fermentation product are significantly improved, and the masterbatch can also be used in a high-fiber bamboo-based feed replacement system, and has good palatability and growth-promoting effect.

Description

Technical Field

[0001] This invention belongs to the field of microbial fermentation and animal nutrition engineering, specifically relating to a method for preparing synthetic biological fermentation yeast feed and its application in bamboo substitute feed. Background Technology

[0002] In recent years, with the increasing prominence of food security issues and the rapid development of the livestock industry, the traditional livestock diet structure, mainly based on corn and soybean meal, is facing the dual pressures of resource scarcity and rising costs. To alleviate the contradiction between feed and grain, developing "non-grain plant resources" as feed substitutes has become a research hotspot. Bamboo plants, due to their abundant biomass, short growth cycle, and non-competition with human grains, have good application prospects in the field of feed substitutes. However, the high lignin content, numerous anti-nutritional factors, and low digestibility of raw bamboo powder severely limit its direct application in diets.

[0003] To address the low utilization rate of bamboo raw materials, some studies have attempted to use fermentation technology for pretreatment, thereby improving nutritional value through microbial decomposition of its structure. However, existing fermented feeds mostly use single-strain or short-term aerobic fermentation, resulting in poor product stability, insufficient functional metabolites, and a lack of targeted release capabilities, making it difficult to meet the demands of modern animal production for precise nutrition and functional regulation.

[0004] In addition, in the field of functional feed additives, small molecule metabolic factors γ-aminobutyric acid (GABA) and indoleacetic acid (IAA) have attracted attention due to their growth-promoting and anti-stress effects. However, most of them are chemically synthesized or exogenously added, which have problems such as high cost, low absorption and utilization rate, and large fluctuations in response. Summary of the Invention

[0005] To address the shortcomings mentioned in the background technology, the present invention aims to provide a method for preparing synthetic biological fermentation feed and its application in bamboo substitute feed. The method employs a multi-strain synergistic fermentation and zinc-containing polyphenol complex induction mechanism, combined with core-shell microcapsule encapsulation technology, to achieve efficient conversion of bamboo raw materials, in-situ enrichment of functional metabolites, and targeted release in the animal digestive tract, thereby improving the nutritional utilization rate and physiological regulatory function of the feed.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for preparing synthetic biological yeast feed includes the following steps:

[0008] S1. Mix bamboo powder, soybean meal, glycerin, yeast extract powder and inorganic salt, add water and stir evenly, sterilize the mixture at high temperature and cool for later use;

[0009] S2. Culture Yeast lipolytica, Aspergillus niger, Lactobacillus brevis and Yeast roux separately, inoculate the bacterial solution into the mixture obtained in step S1, carry out anaerobic fermentation, switch to aeration state for aerobic fermentation, and maintain fermentation conditions until fermentation is complete.

[0010] S3. Dissolve the polyphenol compound in an ethanol-water mixture, add zinc salt solution dropwise, adjust the pH of the system to 7.0-8.5, allow the mixture to stand to crystallize, filter and dry. The resulting product is used as the zinc-containing polyphenol complex inducing factor, and this inducing factor is added to the fermentation system during the induced fermentation stage.

[0011] S4. After fermentation, solid-liquid separation, drying, pulverization and sieving are carried out to obtain yeast powder;

[0012] S5. Add the powder to the sodium alginate solution and stir. Add it dropwise to the calcium chloride solution to form colloidal particles. Take out the colloidal particles and place them in the chitosan solution to react. After the reaction is completed, freeze-dry to obtain the synthetic biological yeast material.

[0013] More preferably, the synthetic biological yeast feed comprises the following raw materials in parts by weight: bamboo powder: 80-120 parts, soybean meal: 20-40 parts, glycerol: 3-8 parts, yeast extract powder: 2-5 parts, inorganic salts: 0.2-0.5 parts, mixed microbial strains: 3-6 parts, zinc-containing polyphenol complex inducing factor: 0.1-0.3 parts, sodium alginate: 1-3 parts, chitosan: 0.5-2 parts;

[0014] The strains include Yersinia lipolytica, Aspergillus niger, Lactobacillus brevis, and Yersinia rouxii.

[0015] More preferably, the mass ratio of each microbial strain in the mixed microbial strain is: Yersinia lipolyticis: Aspergillus niger: Lactobacillus brevis: Yersinia rouxii = 3:2:1:1.

[0016] More preferably, the zinc salt in step S3 is selected from one or more of zinc sulfate, zinc acetate, and zinc chloride, and the polyphenol compound is selected from one or more of gallic acid, tea polyphenols, and proanthocyanidins.

[0017] More preferably, the granules formed in step S5 have a core-shell structure, with the core being yeast powder and the outer shell being a composite of sodium alginate and chitosan, with a shell thickness of 5–15 micrometers.

[0018] More preferably, the synthetic biological yeast feed has a release rate of less than 20% after 1 hour at pH 2.0 and a release rate of more than 80% after 4 hours at pH 6.8.

[0019] More preferably, the yeast feed contains not less than 0.05% γ-aminobutyric acid (GABA), not less than 0.01% indoleacetic acid (IAA), and the total amount of short-chain fatty acids is 0.8% to 1.3%.

[0020] More preferably, the fermentation process adopts a three-stage temperature control mode, including an anaerobic stage, an aerobic stage, and an induction stage, with the temperatures set to 30–32°C, 33–35°C, and 30–34°C respectively, and the durations of each stage being 24 hours, 48 ​​hours, and 12 hours respectively.

[0021] An application of a synthetic biological fermentation yeast feed, which replaces 10% to 20% of the carbon source components in the basal diet, is suitable for feeding pigs, poultry or ruminants to improve feed conversion rate and stress resistance.

[0022] More preferably, under normal temperature and sealed storage conditions, the retention rate of the active ingredients γ-aminobutyric acid and indoleacetic acid in the yeast feed is not less than 90% within 90 days.

[0023] The beneficial effects of this invention are:

[0024] This invention introduces a complex microbial community including *Yersinia lipolyticis*, *Aspergillus niger*, *Lactobacillus brevis*, and *Saccharomyces rouxii* to form an enzyme-microbe synergistic fermentation system. This system effectively degrades anti-nutritional factors and crude fiber structures in bamboo powder, improving the bioavailability of the raw material. Simultaneously, by dynamically controlling the carbon-nitrogen ratio and oxygenation conditions during fermentation, the metabolic direction of the microbial community is precisely induced, leading to the enrichment of short-chain fatty acids, amino acids, and peptides within the system, providing a higher quality nutritional source for animals. Furthermore, this invention utilizes zinc-containing polyphenol complexes as metabolic inducing factors to stimulate microorganisms to synthesize small-molecule active substances γ-aminobutyric acid (GABA) and indoleacetic acid (IAA) with anti-stress and growth-promoting effects at specific stages. This achieves "in-situ efficient generation" of functional metabolites, avoiding the instability and low utilization rate of traditional exogenous additions, and improving the functional density and physiological regulation capabilities of the fermented yeast feed. Meanwhile, by using a core-shell microcapsule encapsulation strategy, a composite membrane was constructed using sodium alginate and chitosan. This protected the stability of the active ingredients while enabling their targeted release in specific parts of the animal digestive tract (such as the small intestine and cecum), significantly improving the bioavailability and targeting efficiency of the active substances and avoiding inactivation in the low pH environment of the stomach. Attached Figure Description

[0025] The invention will now be further described with reference to the accompanying drawings.

[0026] Figure 1 Bar chart showing the comparison of the functional component content of the masterbatch samples from Examples 1-3 and Comparative Examples 1-2;

[0027] Figure 2Radar graphs showing the animal feeding effects of Examples 1-3 and Comparative Examples 1-2. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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] Example 1

[0030] The synthetic biological yeast feed comprises the following raw materials in parts by weight: bamboo powder: 80 parts, soybean meal: 20 parts, glycerol: 3 parts, yeast extract powder: 2 parts, inorganic salts: 0.2 parts, mixed microbial strains: 3 parts, zinc-containing polyphenol complex inducing factor: 0.1 parts, sodium alginate: 1 part, and chitosan: 0.5 parts;

[0031] The strains include Yersinia lipolytica, Aspergillus niger, Lactobacillus brevis, and Yersinia rouxii.

[0032] The preparation steps are as follows:

[0033] S1. Weigh 80g bamboo powder, 20g soybean meal, 3g glycerol, 2g yeast extract, and 0.2g inorganic salt (premixed at a mass ratio of NaCl:KH2PO4 = 1:1). Add 100mL deionized water and stir at 300rpm for 20min until well mixed. Autoclave the mixture at 121°C for 30min, then remove and cool to 30°C for later use.

[0034] S2. Yersinia lipolyticis, Aspergillus niger, Lactobacillus brevis, and Saccharomyces rouxii were inoculated separately into nutrient broth (LB) medium and pre-cultured at 37°C for 24 h. After centrifugation, the bacterial solutions were collected and mixed in a 3:2:1:1 ratio to obtain a mixed bacterial solution. The mixed bacterial solution was inoculated into the mixed substrate from S1 at a ratio of 5%, and anaerobic fermentation was carried out at 30°C for 24 h. Then, the stopper was opened to switch to aerobic fermentation, and fermentation was continued at 150 rpm and 30–32°C for 48 h.

[0035] S3. Take 10 mL of an ethanol-water mixture (3:2), add 0.10 g of gallic acid, dissolve, and then add dropwise 0.05 g of zinc sulfate heptahydrate dissolved in 5 mL of deionized water. Adjust the pH to 7.0 ± 0.2 using 0.1 mol / L NaOH solution. Stir magnetically at 25°C for 2 h, then let stand for 12 h to crystallize. The resulting precipitate is filtered, washed with water, and dried in a 60°C oven for 6 h to obtain a light yellow powder, which is the zinc-containing polyphenol complex inducing factor. Weigh 0.10 g of this inducing factor, dissolve it in 5 mL of sterile water, and add it to the system after 60 h of fermentation. Continue inducing fermentation at 30°C for another 12 h, then stop.

[0036] S4. After fermentation, the system was centrifuged at 8000 rpm for 10 min, the supernatant was discarded, the precipitate was collected and dried in a vacuum drying oven at 50°C for 12 h to constant weight, and then ground in a mortar and pestle and passed through an 80-mesh sieve to obtain fine powdered yeast material.

[0037] S5. Weigh 5g of the above-mentioned yeast starter powder and add it to a 1% (w / v) sodium alginate solution. Stir at 300 rpm for 30 min to form a uniform suspension. Using a syringe, drop the mixture into a 2% calcium chloride solution at a rate of 1 mL / min. After the addition is complete, let it stand for 30 min to complete the ionic cross-linking reaction and form stable gel spheres. Remove the gel spheres, wash them twice with deionized water, and then immerse them in a 1% chitosan solution for 1 h to construct a composite shell structure. Finally, freeze-dry the mixture at −50°C and a vacuum of 10 Pa for 24 h to obtain the synthesized biological yeast starter.

[0038] Application of the synthetic biological yeast feed: The synthesized synthetic biological yeast feed is used as a dietary additive, partially replacing the original carbon source components (mainly corn flour and wheat bran) in the basic diet at a ratio of 10%, and is used to formulate compound feed for pigs.

[0039] Example 2

[0040] The synthetic biological yeast feed comprises the following raw materials in parts by weight: bamboo powder: 120 parts, soybean meal: 40 parts, glycerol: 8 parts, yeast extract powder: 5 parts, inorganic salts: 0.5 parts, mixed microbial strains: 6 parts, zinc-containing polyphenol complex inducing factor: 0.3 parts, sodium alginate: 3 parts, and chitosan: 2 parts.

[0041] The strains include Yersinia lipolytica, Aspergillus niger, Lactobacillus brevis, and Yersinia rouxii.

[0042] The preparation steps of the synthetic yeast starter are the same as in Example 1.

[0043] Application of the synthetic biological yeast feed: The synthesized synthetic biological yeast feed is used as a dietary additive, partially replacing the original carbon source components (mainly corn flour and wheat bran) in the basic diet at a ratio of 20%, and is used to formulate compound feed for pigs.

[0044] Example 3

[0045] The synthetic biological yeast feed comprises the following raw materials in parts by weight: bamboo powder: 100 parts, soybean meal: 30 parts, glycerol: 5.5 parts, yeast extract powder: 3.5 parts, inorganic salts: 0.35 parts, mixed microbial strains: 5 parts, zinc-containing polyphenol complex inducing factor: 0.2 parts, sodium alginate: 2 parts, and chitosan: 1.25 parts;

[0046] The strains include Yersinia lipolytica, Aspergillus niger, Lactobacillus brevis, and Yersinia rouxii.

[0047] The preparation steps of the synthetic yeast starter are the same as in Example 1.

[0048] Application of the synthetic biological yeast feed: The prepared synthetic biological yeast feed is used as a dietary additive to partially replace the original carbon source components (mainly corn flour and wheat bran) in the basic diet at a ratio of 15% in the formulation of compound feed for pigs.

[0049] Comparative Example 1 (without inducing factors)

[0050] The synthetic biological yeast feed comprises the following raw materials in parts by weight: bamboo powder: 100 parts, soybean meal: 30 parts, glycerol: 5.5 parts, yeast extract powder: 3.5 parts, inorganic salts: 0.35 parts, mixed microbial strains: 5 parts, sodium alginate: 2 parts, and chitosan: 1.25 parts;

[0051] The strains include Yersinia lipolytica, Aspergillus niger, Lactobacillus brevis, and Yersinia rouxii.

[0052] The preparation of the synthetic biological yeast feed is the same as in Example 1, except that the preparation and addition of the inducing factor in step S3 are omitted.

[0053] Application of the synthetic biological yeast feed: The prepared synthetic biological yeast feed is used as a dietary additive to partially replace the original carbon source components (mainly corn flour and wheat bran) in the basic diet at a ratio of 15% in the formulation of compound feed for pigs.

[0054] Comparative Example 2 (without coating)

[0055] The synthetic biological yeast feed comprises the following raw materials in parts by weight: bamboo powder: 100 parts, soybean meal: 30 parts, glycerol: 5.5 parts, yeast extract powder: 3.5 parts, inorganic salts: 0.35 parts, mixed microbial strains: 5 parts, and zinc-containing polyphenol complex inducing factor: 0.2 parts;

[0056] The strains include Yersinia lipolytica, Aspergillus niger, Lactobacillus brevis, and Yersinia rouxii.

[0057] The preparation of the synthetic biological yeast feed is the same as in Example 1, except that the sodium alginate and chitosan coating steps are omitted and the fermentation product is simply dried and pulverized to obtain the finished product.

[0058] Application of the synthetic biological yeast feed: The prepared synthetic biological yeast feed is used as a dietary additive to partially replace the original carbon source components (mainly corn flour and wheat bran) in the basic diet at a ratio of 15% in the formulation of compound feed for pigs.

[0059] Performance testing

[0060] 1. Analysis of functional component content

[0061] (1) Content of γ-aminobutyric acid (GABA)

[0062] Take 1 g of each dried sample powder, add 10 mL of 80% ethanol solution, and extract by ultrasonication for 30 min. Centrifuge at 8000 rpm for 10 min and collect the supernatant. Filter through a 0.22 μm filter membrane and then inject for HPLC detection. Chromatographic column: C18 (4.6 × 250 mm, 5 μm); mobile phase: acetonitrile / 0.05 mol·L⁻¹ phosphate buffer = 10:90; flow rate: 1.0 mL·min⁻¹; detection wavelength: 210 nm; injection volume: 10 μL. Calculate the content (mg·g⁻¹) using the GABA standard curve.

[0063] (9) Indoleacetic acid (IAA) content

[0064] Take 1g of sample, add 10mL of methanol solution, and extract by ultrasonication for 30min. Centrifuge and collect the supernatant. Quantitative analysis is performed using enzyme-linked immunosorbent assay (ELISA). High-concentration samples are verified by HPLC. The ELISA kit uses a detection wavelength of 450nm; the standard curve range is 0.1–10μg·mL⁻¹. Results are expressed in μg·g⁻¹.

[0065] (3) Short-chain fatty acids (acetic acid, butyric acid)

[0066] Weigh 2g of sample, add 10mL of deionized water, shake for 30min, and centrifuge. Take 1mL of supernatant, add 10μL of internal standard isobutyric acid, filter through a 0.22μm filter membrane, and inject for gas chromatography analysis. GC conditions: HPFFAP column (30m×0.25mm×0.25μm); injection port temperature 200°C; column temperature increased from 120°C to 200°C (10°C·min⁻¹); carrier gas nitrogen; FID detector 250°C. Quantification was performed using the external standard method (mg·g⁻¹).

[0067] (4) Total amino acid and soluble polypeptide content

[0068] 1 g of sample was added to 10 mL of 6 mol·L⁻¹ HCl and hydrolyzed at 110°C for 24 h. After evaporation to dryness, the sample was diluted to a final volume and loaded onto an amino acid analyzer for total amino acid determination. Soluble peptides were determined using a UV method. The amino acid analyzer used a cation exchange column with a detection wavelength of 570 nm (ninhydrin colorimetric assay). For peptides, absorbance was measured at 280 nm and converted using a BSA standard curve.

[0069] The measurement results are shown in Table 1 below.

[0070] Table 1. Content of functional ingredients

[0071]

[0072] As shown in Table 1, this invention significantly promotes the enrichment of functional metabolites by introducing a zinc-containing polyphenol complex inducing factor and a synergistic fermentation mechanism with a complex microbial community. In Examples 1-3, the contents of γ-aminobutyric acid (GABA), indoleacetic acid (IGA), and short-chain fatty acids were significantly higher than in the comparative examples, indicating that the inducing factor can activate enzyme systems related to amino acid decarboxylation and tryptophan metabolism in the microbial community, enhancing the ability to synthesize functional metabolites. Simultaneously, the sodium alginate-chitosan coating system effectively improved the microenvironmental stability of the fermentation system, reducing the oxidative loss of metabolites. In particular, all indicators in Example 3 reached their highest values, indicating that the carbon-nitrogen balance and induction effect were optimal at this ratio. Compared to Comparative Examples 1 and 2, the overall functional component content was increased by more than 40%.

[0073] 2. Controlled-release performance test

[0074] (1) Acid release rate (gastric juice conditions)

[0075] Take an equal volume of sample (approximately 0.5 g) and incubate it with shaking in 10 mL of simulated gastric fluid (pH 2.0, 37°C) for 1 hour. Collect the supernatant and detect the release of GABA and IAA by HPLC. Calculate the release rate (%) based on the initial content.

[0076] (2) Neutral release rate (small intestinal fluid conditions)

[0077] After 1 hour of treatment with simulated gastric fluid, the same group of samples were replaced with PBS buffer (pH 6.8) and cultured for another 4 hours with shaking in a 37°C water bath. The concentration of functional components released in the solution after 4 hours was analyzed, and the cumulative release rate (%) was calculated.

[0078] (3) Coverage rate

[0079] Take equal amounts of microcapsule samples, break the cell walls with 0.1 mol / L HCl, detect the total amount of GABA / IAA after release, and calculate it by comparing it with the total amount of the corresponding components in the unencapsulated sample.

[0080] The test results are shown in Table 2 below.

[0081] Table 2 Results of controlled-release performance tests

[0082]

[0083] Table 2 shows that the release rates of Examples 1-3 were all below 20% under acidic conditions, while the release rates were all above 80% under neutral conditions, with an encapsulation rate of over 82%. This indicates that the microcapsule encapsulation structure constructed using sodium alginate and chitosan possesses good controlled-release performance and stability. Example 2 used the highest amount of encapsulation material, resulting in the most significant release control effect. Example 3 showed the best performance in terms of release control and process adaptation, demonstrating the synergistic optimization of structure and parameters. Comparative Example 2, lacking encapsulation treatment, experienced a sharp increase in the release rate in gastric juice, reaching 74.2%, leading to a significant decrease in the small intestinal release efficiency to only 58.1%. This verifies that functional components are easily released prematurely or inactivated in the stomach without encapsulation. This invention, through a core-shell carrier structure constructed with composite wall materials, effectively protects the active components and achieves targeted release into the intestine.

[0084] 3. Animal feeding trials

[0085] Weaned piglets (21 days old) with uniform weight and consistent health were selected and divided into 5 groups of 8 piglets each. A control group (Comparative Examples 1 and 2) and an experimental group (Examples 1-3) were established. The experimental period was 30 days. On an isoenergetic and isonitrogenous basis, the yeast feed from Examples 1-3 was added at proportions of 10%, 15%, and 20% respectively to replace part of the corn flour. The results were compared with those of Comparative Examples 1 and 2. The weight of each group of animals was measured daily, and the total weight gain was divided by the number of days to obtain the average daily weight gain (ADG). The feed conversion ratio (F / G) was recorded for each group. The number of individuals with diarrhea was recorded daily, and the incidence rate was calculated. Fecal samples were collected from each group daily, and ammonia gas was tested using a sensor or blind scoring (1-5 points). The results are shown in Table 3 below.

[0086] Table 3 Animal feeding effects

[0087]

[0088] As shown in Table 3, Examples 1-3 outperformed the comparative example in terms of average daily weight gain, feed conversion ratio, diarrhea rate, and fecal ammonia score, with Example 3 showing the most balanced and outstanding performance across multiple indicators. The examples employed a synergistic fermentation strategy of "zinc-containing polyphenol complex inducing factor + compound microbial strain + microencapsulation," which not only improved the enrichment efficiency of functional metabolites but also enhanced the targeted release and absorption of feed in the animal's intestines, improved the intestinal microecological environment, reduced the incidence of diarrhea, and decreased the emission of nitrogenous metabolic waste, demonstrating strong growth-promoting, stress-resistant, and environmentally friendly effects. Compared to Comparative Example 1, Example 3 showed an average daily weight gain increase of approximately 14.3% and a diarrhea rate decrease of nearly half, fully demonstrating the significant nutritional substitution and functional enhancement advantages of this invention in actual feeding systems.

[0089] 4. Storage stability test

[0090] Following the aforementioned functional analysis method (HPLC / ELISA), the remaining GABA and IAA contents of yeast culture samples were determined after 30, 60, and 90 days of storage in a sealed, light-protected, and dry environment at room temperature (25±2°C), and the retention rates were calculated by comparing them with the initial values. A 2g sample was taken and dried at 105°C to constant weight, and the percentage of weight loss was calculated. Changes in powder color, odor, and clumping were recorded using a blind manual evaluation and photographic comparison method (scoring from 1 to 5 points). The stability results after 90 days of storage are shown in Table 4 below.

[0091] Table 4 Storage stability results

[0092]

[0093] As shown in Table 4, Examples 1-3 maintained high GABA and IAA retention rates under 90-day room temperature sealed storage conditions, with Example 3 reaching 94.5% and 93.8% respectively, significantly better than Comparative Examples 1 and 2. This is mainly attributed to the synergistic strategy of "zinc-containing polyphenol complex induction + sodium alginate-chitosan coating" adopted in this invention, which effectively delayed the oxidative degradation of active metabolites, while the coating structure improved the system's resistance to environmental humidity and oxygen fluctuations. Furthermore, the moisture content of the examples was stably controlled below 6%, the sensory score remained above 4.8, the powder was free of caking, and the color and odor were normal, while the comparative samples showed varying degrees of activity loss and sensory deterioration, further verifying the technical advantages and practical application value of this invention in improving the storage stability of functional components.

[0094] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0095] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing synthetic biological yeast feed, characterized in that, Includes the following steps: S1. Mix bamboo powder, soybean meal, glycerin, yeast extract powder and inorganic salt, add water and stir evenly, perform high-temperature sterilization, and cool to obtain a mixture for later use; S2. Yersinia lipolytica, Aspergillus niger, Lactobacillus brevis and Saccharomyces rouxae were inoculated into nutrient broth medium and pre-cultured at 37°C for 24 h. After centrifugation, the bacterial solution was collected and mixed in a ratio of 3:2:1:1 to obtain a mixed bacterial solution. The mixed bacterial solution was added to the mixture obtained in step S1 and fermented in a three-stage temperature control mode, including an anaerobic fermentation stage, an aerobic fermentation stage and an induced fermentation stage. The temperatures were set to 30-32°C, 33-35°C and 30-34°C respectively, and the durations of each stage were 24 hours, 48 ​​hours and 12 hours respectively. S3. Dissolve the polyphenol compound in an ethanol-water mixture, add zinc salt solution dropwise, adjust the pH of the system to 7.0-8.5, allow the mixture to stand to crystallize, filter and dry. The resulting product is used as the zinc-containing polyphenol complex inducing factor, and this inducing factor is added to the fermentation system during the induced fermentation stage. S4. After fermentation, solid-liquid separation, drying, pulverization and sieving are carried out to obtain yeast powder; S5. Add the yeast starter powder to the sodium alginate solution and stir. Add it dropwise to the calcium chloride solution to form colloidal particles. Take out the colloidal particles and place them in the chitosan solution to react. After the reaction is completed, freeze-dry to obtain the synthetic biological yeast starter. The colloidal particles formed in step S5 have a core-shell structure, with the core being yeast powder and the outer shell being a composite of sodium alginate and chitosan, with a shell thickness of 5 to 15 micrometers. The synthetic biological yeast feed exhibits a release rate of less than 20% after 1 hour at pH 2.0 and a release rate of more than 80% after 4 hours at pH 6.

8. The synthetic biological yeast feed contains no less than 0.05% γ-aminobutyric acid, no less than 0.01% indoleacetic acid, and a total of 0.8% to 1.3% short-chain fatty acids.

2. The method for preparing synthetic biological yeast feed according to claim 1, characterized in that, The synthetic biological yeast feed comprises the following raw materials in parts by weight: bamboo powder: 80-120 parts, soybean meal: 20-40 parts, glycerol: 3-8 parts, yeast extract powder: 2-5 parts, inorganic salts: 0.2-0.5 parts, mixed bacterial solution: 3-6 parts, zinc-containing polyphenol complex inducing factor: 0.1-0.3 parts, sodium alginate: 1-3 parts, and chitosan: 0.5-2 parts.

3. The method for preparing synthetic biological yeast feed according to claim 1, characterized in that, The zinc salt mentioned in step S3 is selected from one or more of zinc sulfate, zinc acetate, and zinc chloride, and the polyphenol compound is selected from one or more of gallic acid, tea polyphenols, and proanthocyanidins.

4. The method for preparing synthetic biological yeast feed according to claim 1, characterized in that, Under sealed storage conditions at room temperature, the retention rate of the active ingredients γ-aminobutyric acid and indoleacetic acid in the synthetic biological yeast feed is not less than 90% within 90 days.

5. The application of a synthetic biological yeast feed prepared by the method according to any one of claims 1-4 in the preparation of feed, characterized in that, The prepared synthetic yeast feed can replace 10% to 20% of the carbon source components in the basal diet. It is suitable for feeding pigs, poultry or ruminants to improve feed conversion rate and stress resistance.

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