A composite yeast extract, its preparation method and use

Abstract

The present application provides a kind of composite yeast extract, which is prepared by enzymatic reaction, and the raw materials include yeast, ginger, chrysanthemum, grapefruit peel, the yeast is selected from baker's yeast and / or beer yeast, and the enzyme used is a composite enzyme, preferably including papain, nuclease, cellulase, beta-glucanase, which can be used for livestock feed additives, and has the effects of anti-radiation, improving mating willingness and survival rate of young.

Description

Technical Field

[0001] This invention relates to the fields of yeast extracts and feed, specifically to a herbal compound yeast extract, its preparation method, and its application. Background Technology

[0002] Yeast cells are rich in nutrients and have been used in China for thousands of years. They contain abundant proteins, vitamins, minerals, polysaccharides, and other substances that can promote the growth, development, digestion, and absorption of organisms. Furthermore, the polysaccharides can promote the proliferation of beneficial bacteria, leading to their widespread use in food, feed, brewing beverages, pharmaceuticals, cosmetics, and water treatment. Yeast extracts are produced by the enzymatic degradation of large yeast molecules such as proteins and nucleic acids into smaller molecules, yielding a natural nutritional flavoring substance rich in amino acids, peptides, nucleic acids, vitamins, and trace elements. Current technologies primarily use yeast extracts for flavoring, with applications in feed mainly focused on nutritional supplementation and flavoring. Because the yeast enzymatic hydrolysis process is lengthy, requiring multiple additions of complex enzymes and step-by-step hydrolysis, the preparation process is time-consuming and involves many controllable factors. Additionally, enzymes or other active ingredients in yeast extracts may lose activity during extraction, processing, or storage. Therefore, appropriate methods are needed to protect and stabilize the active ingredients in yeast extracts, such as optimizing extraction conditions, adding protective agents, or using low-temperature storage. Differences may exist between different batches of yeast extracts, leading to variations in their activity or composition. To ensure consistency and reproducibility, standardized extraction and preparation methods need to be established, and extraction process parameters such as temperature, time, and yeast strain selection need to be strictly controlled.

[0003] The complex proteases added during yeast autolysis can hydrolyze peptide bonds, amide bonds, lipid bonds, and polysaccharides in proteins, breaking the cell wall and protein-protein bonds to release nutrients such as proteins, polysaccharides, and nucleic acids. Because there are many types of complex enzymes, and their reaction times and enzymatic hydrolysis conditions vary greatly, different enzymes often need to be added under different conditions in multiple steps to achieve better results, which brings some inconvenience to industrial production. Examples include those disclosed in CN104161259B, CN1481721A, and CN101595808A.

[0004] Traditional Chinese medicine (TCM) herbs, as natural plant-derived ingredients, are inexpensive, have few side effects, are non-toxic, and readily available. Utilizing TCM compound ingredients to replace hormones and antibiotics has potential value. However, the compatibility and interactions between TCM herbs and yeast extracts need to be considered. Current technology lacks records of TCM components acting as yeast enzymatic hydrolysis promoters; if this could be achieved, it would simplify the production process.

[0005] Meanwhile, natural radiation includes ultraviolet radiation, electromagnetic radiation, and nuclear radiation. Environmental radiation problems are becoming increasingly serious, and can have severe effects on animal behavior patterns and the immune system, including attacking intracellular nucleic acid and protein structures, the antioxidant system, and stealing electrons from cells, leading to irreversible damage. This includes antibiotic resistance and epidemics. However, whether it is related to livestock fertility and offspring survival rates is rarely reported. In livestock farming, we often focus on nutritional weight gain or how to shorten the estrus period to increase litter size and survival rate, which are indeed key methods to improve farming efficiency. However, many existing feeds contain large amounts of antibiotics and estrus-inducing ingredients. Although this increases mating rates, it significantly reduces offspring survival rates. This is related to the maternal hormonal environment; the use of estrus-inducing drugs can easily lead to endocrine disorders, and the mother consumes a large amount of nutrients. If the offspring survival rate is low, it will result in negative economic losses. In addition to nutritional factors, environmental conditions, endocrine levels, and other factors also play a role. Furthermore, the use of hormone-containing feeds can also pose safety risks to meat products. Summary of the Invention

[0006] The inventors optimized the yeast extraction process and added compound enzymes and compound traditional Chinese medicine ingredients. They discovered that the traditional Chinese medicine ingredients not only have some auxiliary therapeutic effects, but also produce some "plant enzymes" that promote yeast enzymatic hydrolysis, simplifying the production process. In addition, the compound yeast extract of traditional Chinese medicine, besides increasing the breeding willingness of livestock, also plays an unexpected role in radiation resistance, greatly increasing the survival rate of offspring. This is something that hormone additives cannot achieve. Furthermore, as a feed additive, it contains virtually no organic solvents, antibiotics, or hormones, and has a unique aroma that easily increases feed intake.

[0007] The specific technical solutions include:

[0008] A compound yeast extract is provided, which is prepared by enzymatic hydrolysis of raw materials including yeast, ginger, luteolin, and grapefruit peel. The yeast is selected from baker's yeast and / or brewer's yeast. The enzyme used is a compound enzyme, preferably including papain, nuclease, cellulase, and β-glucanase. The ginger, luteolin, and grapefruit peel are preferably subjected to ultrasonic vibration or microwave treatment to break up cell walls. The ultrasonic vibration frequency is preferably 20-50 kHz, the power is preferably 100-150 W, and the ultrasonic time is preferably 1-3 h. The microwave treatment is performed at a frequency below 2.45 GHz for 10-30 min.

[0009] In a preferred embodiment, yeast is cultured and then extracted using a compound enzyme and a compound herbal medicine. The compound enzyme and compound herbal medicine include: papain, nuclease, cellulase, β-glucanase, ginger, Michelia champaca, and grapefruit peel.

[0010] Furthermore, the raw material composition of the present invention is as follows:

[0011] 1-2 parts yeast

[0012] 1-5 parts of compound enzyme

[0013] 15-25 parts ginger

[0014] 5-15 parts of Michelia champaca

[0015] 5-15 portions of grapefruit peel

[0016] The specific preparation method is as follows:

[0017] 1) Yeast culture:

[0018] Yeast is fed into a yeast tank rich in culture medium and cultured at room temperature to obtain expanded yeast culture liquid, which is then dried to obtain yeast powder.

[0019] The culture medium can be selected from commercially available products (containing glucose, amino acids, tryptone, etc.), or additional nitrogen and carbon sources can be added, or appropriate nutrient growth factors can be added according to the desired health benefits. Amplification can be exponential, with primary seed culture followed by secondary seed culture amplification. A suitable temperature can be selected, such as 20-80℃, preferably 30-60℃, for 5-72 hours, preferably 12-48 hours, after which it can be placed in a fermenter for heat preservation. Preferably, the amount of water added is estimated to ensure that the yeast milk concentration in the prepared yeast tank is 10-15%, and the mixture is stirred evenly. It is then dried.

[0020] 2) After washing the compound herbs, add an appropriate amount of water (compound herbs: water = 1-10: 1-10) and perform ultrasonic vibration or microwave treatment. Add compound enzyme and stir to obtain a compound enzyme-herb mixture.

[0021] Preferably, the weight ratio of ginger:mignonette:pomelo peel is 3-6:1-3:1-3; preferably, the compound enzyme includes, but is not limited to, papain, nuclease, cellulase, β-glucanase, etc.; the weight ratio of the compound enzyme is papain:nuclease:cellulase:β-glucanase = 1-3:1-3:1-3:1-3; the weight ratio of compound enzyme to compound herbal medicine is 1:5-60; the weight ratio of yeast:compound enzyme is 1-5:1-5;

[0022] 3) Add the yeast powder obtained in 1) to an appropriate amount of water to prepare a suspension with a concentration of 10-15%, add it to a yeast tank containing the above-mentioned compound enzyme herbal mixture, heat to above 50°C, and autolytically hydrolyze for no less than 2 hours; heat to above 90°C and maintain for 30 minutes to inactivate the enzyme; separate by sieve filtration, and dry the filter residue.

[0023] The preferred enzymatic hydrolysis temperature is 50-65℃, the time is 2-24h, preferably 4-20h, and the pH in the yeast tank is preferably 4.5-6.5; the preferred enzyme inactivation temperature is 90-130℃, optimally 90-110℃, and the enzyme inactivation time is 10-30min, preferably 15-20min; filtration is performed using a 60-80 mesh sieve.

[0024] 4) The filtered clear liquid is vacuum concentrated and then spray-dried to obtain powdered compound yeast extract; the finished product is packaged and inspected.

[0025] The preferred air inlet temperature for spray drying is 180±10℃, and the preferred air outlet temperature is 180±10℃.

[0026] The concentration process can be operated as follows: First, cooling water is introduced through the circulating pump, discharge pump, and condensate pump. A certain amount of liquid is then introduced. The vacuum hydraulic jet pump is turned on, the vacuum level is adjusted, and the inlet valve is opened to begin concentration. The feed rate and steam valve are adjusted to control the temperature of the first effect at 85±10℃, the second effect at 75±10℃, and the third effect at 65±10℃. Before the product meets the process requirements, a small amount of liquid should be released, and the concentration measured with a Baumé meter. Once it reaches 18-25 Bx (solids concentration 25-45%), the liquid is discharged and sent to the next drying process.

[0027] Specifically, the filter residue is fed into a preheated drum, and the drum speed and steam usage are adjusted according to the degree of dryness. The resulting flaky / powdered filter residue is then allowed to cool naturally before being packed into woven bags. Once a certain quantity is collected, it is further dried, pulverized, inspected, and packaged.

[0028] This invention also relates to the application of a compound yeast extract in the preparation of feed additives, wherein the additives include the above-mentioned compound yeast extract and the dried filter residue from the preparation process, the filter residue mainly comprising the solid residue after enzymatic hydrolysis and extraction of compound herbs.

[0029] This invention also relates to a method for preparing livestock feed additives containing compound yeast extracts, comprising the following steps:

[0030] 1) Yeast culture:

[0031] Yeast is added to a yeast tank rich in culture medium, and the expanded yeast culture is obtained by culturing at room temperature and then dried.

[0032] 2) After washing the compound herbs, add an appropriate amount of water (compound herbs: water = 1-10: 1-10) and perform ultrasonic vibration or microwave treatment. Add compound enzyme and stir to obtain a compound enzyme-herb mixture.

[0033] 3) Add an appropriate amount of water to the yeast liquid obtained in 1) to prepare a suspension with a concentration of 10-15%, add it to the yeast tank containing the above-mentioned compound enzyme herbal mixture, heat to above 50°C, and autolytic enzymatic hydrolysis for no less than 3 hours; heat to above 90°C and maintain for 30 minutes to inactivate the enzyme; separate by sieve filtration, and dry the filter residue.

[0034] 4) The filtered clear liquid is vacuum concentrated and then spray-dried to obtain a powdered compound yeast extract; the compound yeast extract is mixed with the dried filter residue from step 3) to obtain the final product.

[0035] The livestock feed additive of the present invention can be used to prepare products for the prevention or treatment of livestock radiation diseases, as well as products that improve livestock breeding willingness and offspring survival rate.

[0036] The drying method described in this invention can also use vacuum drying and filtration, with a vacuum pressure of 10-100 mbar, preferably 20-80 mbar, and more preferably 40-60 mbar. The supernatant is collected from the filtrate. The filter residue is dried in a drum after discharge, then pulverized in a pulverizer and processed separately.

[0037] In a preferred embodiment, the yeast extract process of the present invention is simple and controllable. The enzymatic hydrolysis step does not require multiple enzyme additions. Simply open the steam valve, stir and heat, control the temperature of the liquid, and contact the filtration station to release the material after a certain period of enzymatic hydrolysis.

[0038] In this invention, the papain, nuclease, cellulase, and β-glucanase in the compound enzyme were all purchased from Guangzhou Weber Technology Co., Ltd. and Nanning Pangbo Biotechnology Co., Ltd. (Q / NPB 31-2014); the yeast culture medium was purchased from Shanghai Jiachu Biotechnology Co., Ltd.

[0039] The remaining compounds were purchased from Merck (Sigma), and the detection equipment was purchased from Mettler Toledo Instruments Ltd.

[0040] Baker's yeast (Saccharomyces cerevisiae) CICC31616 is a strain preserved at the China Industrial Microbial Culture Collection Center, which can be obtained by the public through purchase.

[0041] The brewer's yeast strain was deposited at the China General Microbiological Culture Collection Center (CGMCC) on December 26, 2016, with accession number CGMCC No. 13500.

[0042] The brewer's yeast was purchased from China Resources Snow Breweries (Zhejiang) Co., Ltd. (QC / TCS 001-2015). The sample was dissolved and diluted in sterile physiological saline and then cultured. DNA detection showed that it was homologous to the brewer's yeast strain with CGMCC No.13500 and had a purity of over 99.9%.

[0043] The baker's yeast strain was purchased from Xi'an Ruixi Biotechnology Co., Ltd. The sample was dissolved and diluted in sterile physiological saline and then cultured. DNA detection showed that the gene sequence was homologous to strain CICC31616, with a purity higher than 99.9%.

[0044] Lactobacillus rhamnosus was purchased from Xi'an Baichuan.

[0045] Lactobacillus rhamnosus strain LR863 is deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 14410. The Lactobacillus rhamnosus strain purchased in this invention, based on rRN sequence analysis and API bacterial identification system analysis, shows homology and 99.9% purity to the aforementioned deposited strain.

[0046] The livestock mentioned in this invention refer to livestock industry animals used for milk production, meat production, reproduction, or fur production, and examples include, but are not limited to, cattle, sheep, pigs, horses, and donkeys.

[0047] The terms "comprising," "including," or any other variations thereof in this invention are intended to cover a non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the product or system comprising said element. Room temperature as used in this invention refers to 15-25°C. Unless otherwise specified, all percentages in this invention represent weight percentages, and unless otherwise stated, a solution in this invention refers to an aqueous solution.

[0048] The beneficial effects of this invention are:

[0049] 1) Avoid using organic solvents, antibiotics and hormones. The raw materials are natural, readily available, non-toxic and have no side effects.

[0050] 2) The yeast extraction process has been improved by using a specific compound enzyme and compound herbs. After the herbs are broken down, some plant components that can synergistically promote enzymatic hydrolysis are produced, which can save on the addition of compound enzymes, simplify the industrialization process and make it controllable.

[0051] 3) Supplementing nutrients improves fertility and unexpectedly reveals anti-radiation effects, significantly reducing miscarriage and offspring mortality. While simple use of estrus-inducing drugs can increase mating, it results in high miscarriage rates and low survival rates, ultimately increasing breeding costs. Attached Figure Description

[0052] Figure 1 Flowchart of industrial production of yeast extract. Detailed Implementation

[0053] Example 1: Compound yeast extract

[0054] 1) Yeast culture to obtain amplified yeast cells:

[0055] Brewer's yeast was inoculated into a commercially available culture medium and cultured at room temperature for 48 hours. The culture medium in the exponential growth phase was used as the primary seed culture and inoculated into a secondary seed tank to achieve exponential expansion. The resulting yeast liquid was filtered and dried to obtain yeast powder.

[0056] 2) After washing the compound herbs (ginger: Michelia champaca: grapefruit peel = 3:2:2), add 5 times the amount of water and ultrasonically vibrate at 150W for 1 hour to break the cell wall. Then add the compound enzyme (papain: nuclease: cellulase: β-glucanase = 2:2:1:1) and stir to obtain a compound enzyme-herb mixture.

[0057] 3) Add the yeast powder obtained in 1) to an appropriate amount of water to prepare a 10-15% concentration suspension. Add this suspension to a yeast tank containing the above-mentioned compound enzyme-herb mixture, adjust the pH range to 4.5-6.5, heat to 60℃, and autolyze for 4 hours; then heat to 95℃ and maintain for 30 minutes to inactivate the enzyme; filter and separate using a 60-80 mesh sieve, leaving the clear liquid. Dry the filter residue (push the filter residue into a preheated drum, adjust the drum speed and steam usage according to the degree of dryness; after the drum-dried flake-powdered filter residue has cooled naturally, pack it into woven bags).

[0058] 4) The clarified liquid remaining after filtration and separation is then vacuum concentrated. The vacuum concentration process can be operated as follows: Cooling water is introduced into the circulating pump, discharge pump, and condensate pump. A certain amount of liquid is then introduced. The vacuum hydraulic jet pump is turned on, the vacuum level is adjusted, and the air inlet valve is opened to begin concentration. The feed rate and steam valve are adjusted to control the temperature of the first effect at 85±10℃, the second effect at 75±10℃, and the third effect at 65±10℃. Before the product meets the process requirements, a small amount of liquid should be released, and the concentration measured with a Baumé meter. Once it reaches 18-25 Bx (solids concentration 25-45%), the liquid is discharged and sent to the next drying process.

[0059] After concentration, the product is spray-dried to obtain a powdered compound yeast extract; the finished product is then packaged and inspected. The spray drying inlet air temperature is 180±10℃, and the outlet air temperature is 180±10℃.

[0060] Detection method:

[0061] The extract was analyzed by high-performance liquid chromatography (HPLC) using an HP1100 instrument running ChemStation software. The HPLC conditions were as follows:

[0062] • Separation column: Asahipak HPLC column GS-320 (30℃, 7.5mm×300mm)

[0063] • Mobile phase: 0.1M sodium phosphate buffer (pH 7.0)

[0064] • Flow rate: 1.0 mL / min

[0065] • Detection: Ultraviolet detector (260nm)

[0066] Polyacrylamide gel electrophoresis (Invitrogen) was used to detect the protein characteristics of the hydrolysis products. NuPAGEMES migration buffer was used for protein migration, SeeBluePlus2 was used as a molecular weight marker, and Coomassie Blue R-250 was used for protein staining. High molecular weight proteins, dextran, and mannan were detected in the filter residue, with a total amino acid content of 35% and peptides of 18%.

[0067] Example 2: Compound yeast extract

[0068] The yeast was replaced with baker's yeast, and everything else was the same as in Example 1. HPLC analysis showed that the total amino acid content was 30% and the peptide content was 28%.

[0069] Example 3: Compound yeast extract (excluding traditional Chinese medicine)

[0070] Without adding the traditional Chinese medicine complex, the preparation steps were the same as in Example 1. However, due to insufficient enzymatic hydrolysis, it was necessary to add the complex once during the process, and the enzymatic hydrolysis time was extended to 16 hours. HPLC analysis showed that the total amino acids were 20% and the polypeptides were 18%, which was much lower than in Examples 1-2.

[0071] Example 4: Compound yeast extract (converting compound enzyme)

[0072] The compound enzyme was replaced with alkaline protease, and the yeast culture broth was subjected to steam sterilization for 15-50 seconds to disrupt the cell walls. The pH of the yeast tank was adjusted to 7.5-8, and the alkaline protease was added. The remaining steps were the same as in Example 1. The obtained extract product contained 18% total amino acids and 7% polypeptides.

[0073] The preparation and testing of the extracts above show that although the yeast underwent cell wall disruption pretreatment in Example 4, the enzymatic hydrolysis was still insufficient. This indicates that the herbal compound did not play a synergistic role in the enzymatic hydrolysis of yeast by the alkaline protease. The herbal compound and the compound enzyme in this invention have a mutually promoting and synergistic effect and are selective. In addition, Example 3 shows that the enzymatic hydrolysis reaction is supplemented and time is saved in the presence of herbal medicine.

[0074] Example 5 (Livestock Feed Additive)

[0075] The compound yeast extract of Example 1 was mixed with the dried filter residue (mainly containing Chinese herbal medicine residue) produced in step 3) of its preparation process to prepare a livestock feed additive containing compound yeast extract.

[0076] Example 6 (Livestock Feed Additive)

[0077] The compound yeast extract of Example 2 was mixed with the dried filter residue (mainly containing Chinese medicine residue) produced in step 3) of its preparation process, and Rhamnosus was added to prepare a livestock feed additive.

[0078] Example 7 (Livestock feed additive, Chinese medicine ingredients only)

[0079] After washing the compound herbs (ginger: luteolin: grapefruit peel = 3:2:2), add 5 times the amount of water and perform ultrasonic vibration treatment at 150W for 1 hour. After concentration and drying, a livestock feed additive is prepared.

[0080] Example 8 (Livestock Feed Additive)

[0081] The compound yeast extract of Example 4 was mixed with the dried filter residue (mainly containing Chinese herbal medicine residue) produced in step 3) of its preparation process to prepare a livestock feed additive.

[0082] Compare with Example 1:

[0083] Commercially available hormone-containing estrus-inducing agents for livestock are added to ordinary feed.

[0084] Experiment 1:

[0085] To verify the effectiveness of this invention in promoting livestock mating and improving the survival rate of conceived piglets, adult sows were randomly divided into a control group and an experimental group, with 20 sows in each group. The estrus and conception rate, piglet survival rate (30-day survival rate), and weight gain (after 25 days of feeding) of sows were recorded 15 days after weaning.

[0086] Control group: The control group used commercially available yeast extract products (e.g., purchased from Angel Yeast Co., Ltd.).

[0087] The compound yeast extract or feed additives from the above examples, control examples, and blank groups were added to conventional feed and fed 1-2 kg three times a day.

[0088] The results are shown in Table 1 below:

[0089] Table 1

[0090]

[0091] The above experiments show that Examples 1-2, as compound yeast extracts, significantly increased the mating rate, especially the survival rate of piglets. However, Examples 3-4, extracts without herbal enzymatic hydrolysis or modified compound enzymes, showed significantly lower mating and piglet survival rates. This may be because the amino acids and small peptides produced during enzymatic hydrolysis interact with the herbal extracts, exhibiting estrus-inducing and pregnancy-protecting effects, thus improving piglet survival. Feed additives containing herbal residue had a significant positive impact on weight gain. However, pure herbal additives resulted in poor appetite and weight gain in piglets due to feeding intolerance; while piglet survival was acceptable, conception rates were low. Commercially available yeast extracts alone showed the lowest overall performance. While feed additives containing hormones could improve mating and conception rates, they did not significantly increase piglet survival rates.

[0092] Test 2: Radiation Resistance Test

[0093] 1) Adult sows were randomly divided into a control group and experimental groups, with 20 sows in each group. They were irradiated with continuous microwave radiation at a frequency of 2450 MHz for 3 days to study the effect of feed additives on microwave radiation. Peripheral blood cells, namely white blood cells (WBC) and platelets (PTS), bone marrow DNA (DNA-B), and serum SOD (superoxide dismutase) activity were recorded. The results are shown in Table 2.

[0094] Table 2

[0095]

[0096] 2) Adult sows were randomly divided into a control group and experimental groups, with 20 sows in each group. [The following text appears to be a separate, unrelated sentence:] ...using... 60 Micro-dose scattering of Co-γ rays (2-5 Gy) was performed, followed by continued feeding after irradiation, with testing conducted 10 days later. It is important to note that high-dose radiation can directly cause death or injury to livestock that cannot be reversed by medication, and high-dose nuclear radiation is extremely rare in the actual environment.

[0097] Record peripheral blood cell counts, including white blood cells (WBC) and platelets (PTS), bone marrow DNA (DNA-B), and serum SOD (superoxide dismutase) activity. See Table 3.

[0098] Table 3

[0099]

[0100] The results showed that the compound yeast extract of this invention significantly improved the protection of blood counts in livestock after radiation exposure. According to the Ministry of Health's evaluation standards for auxiliary protection against radiation hazards, it has an auxiliary protective function against radiation hazards. In addition to protecting against radiation hazards, the inventors found that it also had a good protective effect against radiation-induced abortion in pregnant sows. Compared with the control and blank groups, although some sows had increased conception, all of them aborted in the radiation experiment. However, the abortion rate in sows in Examples 1-2, and especially Examples 5-6, was reduced by more than 50%, and the abortion rate in Example 4 was also reduced. This indicates that the feed additive of this invention has a protective effect against both electromagnetic radiation and radioactive material radiation at low doses. Its mechanism may be related to improved immunity and cellular antioxidant capacity, or it may be related to blood count protection. The use of traditional Chinese medicine alone or the compound yeast extract alone did not show a significant advantage compared to the control and blank groups.

[0101] The specific embodiments described above do not constitute a limitation on the scope of protection of the present invention. Those skilled in the art can make various changes and applications to the present invention based on the above description.

Claims

1. A compound yeast extract used as a livestock feed additive, characterized in that, The raw materials are prepared by enzymatic hydrolysis, and the composition of the raw materials is as follows: 1-2 parts yeast 1-5 parts of compound enzyme 15-25 parts ginger 5-15 parts of Michelia champaca 5-15 portions of grapefruit peel; The yeast is selected from baker's yeast and / or brewer's yeast, and the complex enzyme is a combination of papain, nuclease, cellulase and β-glucanase.

2. The method for preparing the compound yeast extract according to claim 1, comprising the following steps: 1) Yeast culture: Yeast was added to a yeast tank rich in culture medium and cultured at room temperature to obtain expanded yeast culture solution, which was then dried. 2) After washing the compound herbs, add an appropriate amount of water, wherein the ratio of compound herbs to water is 1-10:1-10, and perform ultrasonic vibration or microwave treatment. Add compound enzyme and stir to obtain a compound enzyme-herb mixture; wherein the compound herbs are the combination of ginger, Michelia champaca and pomelo peel as described in claim 1; and the compound enzyme is the combination of papain, nuclease, cellulase and β-glucanase as described in claim 1. 3) Add the yeast obtained in 1) to an appropriate amount of water to prepare a suspension with a concentration of 10-15%, add it to a yeast tank containing the above-mentioned compound enzyme herbal mixture, heat to above 50°C, and enzymatically hydrolyze for no less than 3 hours; heat to above 90°C and maintain for 30 minutes to inactivate the enzyme; separate by sieve filtration, and dry the filter residue. 4) The filtered clear liquid is vacuum concentrated and then spray-dried to obtain powdered compound yeast extract; the finished product is packaged and inspected.

3. The application of the compound yeast extract according to claim 1 in the preparation of feed additives.

4. A method for preparing a livestock feed additive, comprising the following steps: 1) Yeast culture: Yeast was added to a yeast tank rich in culture medium and cultured at room temperature to obtain expanded yeast culture solution, which was then dried. 2) After washing the compound herbs, add an appropriate amount of water, wherein the ratio of compound herbs to water is 1-10:1-10, and perform ultrasonic vibration or microwave treatment. Add compound enzyme and stir to obtain a compound enzyme-herb mixture; wherein the compound herbs are the combination of ginger, Michelia champaca and pomelo peel as described in claim 1; and the compound enzyme is the combination of papain, nuclease, cellulase and β-glucanase. 3) Add an appropriate amount of water to the yeast liquid obtained in 1) to prepare a suspension with a concentration of 10-15%, add it to the yeast tank containing the above-mentioned compound enzyme herbal mixture, heat to above 50°C, and enzymatically hydrolyze for no less than 3 hours; heat to above 90°C and maintain for 10-30 minutes to inactivate the enzyme; separate by sieve filtration, and dry the filter residue. 4) The filtered clear liquid is vacuum concentrated and then spray-dried to obtain a powdered compound yeast extract; the compound yeast extract is mixed with the dried filter residue from step 3) to obtain the final product.

5. The livestock feed additive prepared by the method of claim 4.

6. The livestock feed additive of claim 5, used in the preparation of products that improve the breeding willingness of livestock and the survival rate of offspring.

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