Selenomethionine feed additive and preparation method thereof

Abstract

The invention relates to the technical field of feed additives, and particularly discloses a selenomethionine feed additive and a preparation method thereof.The preparation method of the feed additive comprises the steps that wheat flour, a synthetic precursor, KH2PO4 and MgSO4 are added into navel orange residues and mixed to be uniform, then a fermentation substrate is obtained, the moisture content of the fermentation substrate is controlled, and the fermentation substrate is fermented under the condition that the pH ranges from 4 to 8; the preparation method comprises the following steps: inoculating a composite strain capable of producing glutathione reductase, uniformly mixing, controlling the fermentation temperature, fermenting for 10-20 days, inoculating bacillus capable of producing methionine synthetase, fermenting for 10-15 days, drying and crushing to obtain the selenomethionine feed additive. The prepared feed additive is high in organic selenium content, selenomethionine accounts for more than 50% of the total selenium content, the highest selenomethionine accounts for 73.11%, the standard of the feed additive is met, the preparation method is environmentally friendly, and the requirement for production environment conditions is low.

Description

Technical Field

[0001] The present application relates to the technical field of feed additives, and more specifically, to a selenomethionine feed additive and a preparation method thereof. Background Art

[0002] Navel orange pomace is the primary byproduct of juicing navel oranges. It's high in sugar and water, but because fresh pomace is prone to mold and difficult to preserve, has poor palatability, low protein content, and low digestibility, it's mostly disposed of as waste, contributing to environmental problems like soil acidification and water eutrophication. While some regions are experimenting with using fresh pomace as ruminant feed, its nutritional deficiencies limit resource utilization.

[0003] Selenium is an essential trace element for animal growth and development, and selenium deficiency can severely impact animal growth and the quality of livestock products. However, traditional inorganic selenium sources (sodium selenite) have significant drawbacks, including high toxicity and low absorption. Inorganic selenium sources have a narrow safety threshold, are prone to poisoning, and require strict mixing uniformity to avoid localized overdose. While organic selenium (such as yeast selenium) offers reduced toxicity and improved absorption, its production cost is high and it relies on imported strains or processes, making it difficult to meet scale-up requirements. Therefore, there is an urgent need to develop a low-toxic, highly absorbable, and low-cost selenomethionine-containing feed additive and its preparation method, thereby establishing an efficient bioconversion system for navel orange pulp resources. Summary of the Invention

[0004] In order to solve the technical problems mentioned in the background technology, the present application provides a selenomethionine feed additive and a preparation method thereof.

[0005] A method for preparing a selenomethionine feed additive comprises the following steps: After crushing and sieving the navel orange residue, wheat flour, synthetic precursor, KH2PO4 and MgSO4 are added, and the mixture is evenly mixed to obtain a fermentation substrate. The moisture content of the fermentation substrate is controlled to be 40-65%. At a pH of 4-8, a composite strain of bacteria producing glutathione reductase is inoculated, and the mixture is evenly mixed. The fermentation temperature is controlled to be 20-32°C, and the mixture is fermented for 10-20 days. Then, Bacillus producing methionine synthase is inoculated, and the mixture is fermented for 10-15 days. The mixture is dried at a temperature of 40-65°C, and crushed to obtain a selenomethionine feed additive.

[0006] Preferably, the mass ratio of the navel orange pulp, wheat flour, synthetic precursor, KH2PO4 and MgSO4 is 10-80:15-85:0.1-5:0.01-0.5:0.01-0.5.

[0007] Preferably, the synthetic precursor consists of sodium selenite and cysteine in a mass ratio of 0.6-0.8:1.

[0008] Preferably, the synthetic precursor consists of sodium selenite and cysteine in a mass ratio of 0.7:1.

[0009] Preferably, the composite bacterial strain producing glutathione reductase is composed of Pichia pastoris, Streptomyces and Lactobacillus plantarum with an effective viable cell count of 10-12:2-4:1-3.

[0010] Preferably, the methionine synthase-producing Bacillus is Bacillus licheniformis and / or Bacillus subtilis.

[0011] Preferably, the inoculation amount of the glutathione reductase-producing composite bacterial strain is 5-15% of the fermentation substrate.

[0012] Preferably, the inoculation amount of the methionine synthase-producing Bacillus is 8-15% of the fermentation substrate.

[0013] A selenomethionine feed additive is prepared by the above method.

[0014] In summary, this application has the following beneficial effects: In the process of synthesizing selenomethionine feed additive, the present application realizes efficient conversion of sodium selenite to selenomethionine by inoculating a composite strain producing glutathione reductase and a Bacillus producing methionine synthase in stages. In the first stage, a composite bacterial strain producing glutathione reductase is inoculated. Pichia pastoris can efficiently secrete glutathione reductase, which can reduce high-valent inorganic selenium (such as sodium selenite) to low-valent selenium (such as hydrogen selenide), providing a key intermediate for the subsequent synthesis of organic selenium. At the same time, its vigorous sugar metabolism can utilize the carbohydrates in wheat flour to provide energy for the entire fermentation system. Streptomycin can not only secrete a variety of extracellular enzymes (such as proteases and amylases) to degrade complex components such as cellulose and pectin in navel orange pomace, but also release small molecule carbon and nitrogen sources (such as glucose and amino acids) to optimize the availability of fermentation substrates. The secondary metabolites it produces can inhibit contamination by foreign bacteria and maintain a stable fermentation environment. Lactobacillus plantarum maintains the system by producing acids (such as lactic acid). On the one hand, it matches the optimal growth environment of Pichia pastoris, and on the other hand, it inhibits the reproduction of harmful microorganisms and ensures the specificity of fermentation direction. The short-chain fatty acids accumulated during its metabolism can promote the subsequent colonization and enzyme expression of Bacillus licheniformis. The synergistic fermentation of the three bacterial species not only achieves the efficient conversion of sodium selenite to selenocysteine, significantly improving the selenium conversion rate, but also reduces sterilization costs through pH self-regulation. In the second stage, methionine synthase-producing Bacillus licheniformis is inoculated. Bacillus licheniformis secretes highly active methionine synthase, which converts selenocysteine into selenomethionine. Through staged fermentation, in the first stage, the glutathione reductase-producing bacterial community prioritizes selenium reduction. In the second stage, the methionine synthase-producing Bacillus licheniformis focuses on methionine synthesis, avoiding enzyme inhibition and achieving efficient conversion of inorganic selenium to organic selenium.

[0015] In the present application, the efficient conversion of sodium selenite to selenomethionine is achieved by regulating the feed ratio of sodium selenite and cysteine. Sodium selenite, as an inorganic selenium source, provides selenium while avoiding its excessive toxicity. The appropriate ratio not only meets the substrate requirements of the glutathione reductase-catalyzed reduction reaction, but also should prevent the inhibition of microbial growth by high concentrations of sodium selenite. Cysteine, as a precursor substance for methionine synthesis, can provide sulfhydryl groups and carbon skeletons, combine with selenium ions to form selenocysteine intermediates, directly participate in the methionine synthase-catalyzed reaction of Bacillus licheniformis, shorten the metabolic pathway, and improve the yield of the target product. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The conversion rate of selenomethionine after fermentation at different feed ratios of cysteine and sodium selenite.

[0017] Figure 2 Schematic diagram of the biological process for the synthesis of selenomethionine feed additive. DETAILED DESCRIPTION

[0018] The present application is further described in detail below with reference to the examples. Wheat flour (food grade) used in the examples and comparative examples of the present application was purchased from Hebei Chuangzhiyuan Biotechnology Co., Ltd.; sodium selenite (feed grade) was purchased from Guangdong Mingtong Biotechnology Co., Ltd.; cysteine (food grade) was purchased from Shandong Xinxiong Biotechnology Co., Ltd.; Pichia manshurica (product name: Pichia manshurica, product number: B336087), Streptomyces sp. (product name: Streptomyces sp., product number: BMZ126915), Lactobacillus plantarum (product name: Lactobacillus plantarum, product number: B94687); and Bacillus licheniformis (product name: B66977) were all purchased from Ningbo Mingzhou Biotechnology Co., Ltd.

[0019] Example 1-3 provides a selenomethionine feed additive and a preparation method thereof.

[0020] Example 1 A method for preparing a selenomethionine feed additive comprises the following steps: The navel orange pulp was crushed and passed through a 10 mm sieve. Wheat flour, synthetic precursors KH2PO4 and MgSO4 were added and mixed evenly to obtain a fermentation substrate. The moisture content of the fermentation substrate was controlled to be 40%. At a pH of 4, a composite strain of glutathione reductase-producing bacteria was inoculated at an inoculum amount of 5% of the fermentation substrate. The mixture was mixed evenly. The fermentation temperature was controlled at 20°C and fermented for 10 days. Then, a Bacillus sp. producing methionine synthase was inoculated at an inoculum amount of 8% of the fermentation substrate. The fermentation was continued for 10 days at a temperature of 40°C. ℃, drying, and crushing to obtain a selenomethionine feed additive, wherein the mass ratio of navel orange pulp, wheat flour, synthetic precursor, KH2PO4 and MgSO4 is 10:15:0.1:0.01:0.01, the synthetic precursor is composed of sodium selenite and cysteine in a mass ratio of 0.6:1, the glutathione reductase-producing composite bacteria is composed of Pichia pastoris, Streptomyces and Lactobacillus plantarum in an effective viable count of 10:2:1, and the methionine synthase-producing Bacillus is Bacillus licheniformis.

[0021] Example 2 A method for preparing a selenomethionine feed additive comprises the following steps: The navel orange pulp was crushed and passed through a 25 mm sieve, and wheat flour, synthetic precursors KH2PO4 and MgSO4 were added and mixed evenly to obtain a fermentation substrate. The moisture content of the fermentation substrate was controlled to be 50%. At a pH of 6, a composite strain of glutathione reductase was inoculated at an inoculation amount of 10% of the fermentation substrate. The mixture was mixed evenly. The fermentation temperature was controlled at 26°C and fermented for 15 days. Then, a Bacillus subtilis producing methionine synthase was inoculated at an inoculation amount of 12% of the fermentation substrate. The fermentation was continued for 12 days. The selenomethionine feed additive is prepared by drying and crushing at 50°C, wherein the mass ratio of navel orange pulp, wheat flour, synthetic precursor, KH2PO4 and MgSO4 is 50:60:3:0.2:0.2, the synthetic precursor is composed of sodium selenite and cysteine in a mass ratio of 0.7:1, the composite bacteria for producing glutathione reductase is composed of Pichia pastoris, Streptomyces and Lactobacillus plantarum in an effective live bacteria count of 11:3:2, and the Bacillus producing methionine synthase is Bacillus licheniformis.

[0022] Example 3 A method for preparing a selenomethionine feed additive comprises the following steps: The navel orange pulp was crushed and passed through a 35 mm sieve, and wheat flour, synthetic precursors KH2PO4 and MgSO4 were added and mixed evenly to obtain a fermentation substrate. The moisture content of the fermentation substrate was controlled to be 65%. At a pH of 8, a composite strain of glutathione reductase was inoculated at an inoculation amount of 15% of the fermentation substrate. The mixture was mixed evenly, and the fermentation temperature was controlled at 32°C. The fermentation was carried out for 20 days. Then, a Bacillus subtilis producing methionine synthase was inoculated at an inoculation amount of 15% of the fermentation substrate. The fermentation was carried out for 15 days. The method comprises the following steps: drying at 65°C, drying and crushing to obtain a selenomethionine feed additive, wherein the mass ratio of navel orange pulp, wheat flour, synthetic precursor, KH2PO4 and MgSO4 is 80:85:5:0.5:0.5, the synthetic precursor is composed of sodium selenite and cysteine in a mass ratio of 0.8:1, the composite bacteria for producing glutathione reductase is composed of Pichia pastoris, Streptomyces and Lactobacillus plantarum in an effective viable count of 12:4:3, and the Bacillus producing methionine synthase is Bacillus licheniformis.

[0023] Comparative Example 1 A method for preparing a selenomethionine feed additive comprises the following steps: The navel orange pulp was crushed and passed through a 25 mm sieve, and wheat flour, synthetic precursors KH2PO4 and MgSO4 were added and mixed evenly to obtain a fermentation substrate. The moisture content of the fermentation substrate was controlled to be 50%. At a pH of 6, a composite strain of glutathione reductase was inoculated at an inoculation amount of 10% of the fermentation substrate. The mixture was mixed evenly. The fermentation temperature was controlled at 26°C and fermented for 15 days. Then, a Bacillus subtilis producing methionine synthase was inoculated at an inoculation amount of 12% of the fermentation substrate. The fermentation was continued for 12 days. The selenomethionine feed additive is prepared by drying and crushing at 50°C, wherein the mass ratio of navel orange pulp, wheat flour, synthetic precursor, KH2PO4 and MgSO4 is 50:60:3:0.2:0.2, the synthetic precursor is composed of sodium selenite and cysteine in a mass ratio of 0.4:1, the composite bacteria for producing glutathione reductase is composed of Pichia pastoris, Streptomyces and Lactobacillus plantarum in an effective live bacteria count of 11:3:2, and the Bacillus producing methionine synthase is Bacillus licheniformis.

[0024] Comparative Example 2 A method for preparing a selenomethionine feed additive comprises the following steps: The navel orange pulp was crushed and passed through a 25 mm sieve, and wheat flour, synthetic precursors KH2PO4 and MgSO4 were added and mixed evenly to obtain a fermentation substrate. The moisture content of the fermentation substrate was controlled to be 50%. At a pH of 6, a composite strain of glutathione reductase was inoculated at an inoculation amount of 10% of the fermentation substrate. The mixture was mixed evenly. The fermentation temperature was controlled at 26°C and fermented for 15 days. Then, a Bacillus subtilis producing methionine synthase was inoculated at an inoculation amount of 12% of the fermentation substrate. The fermentation was continued for 12 days. The selenomethionine feed additive is prepared by drying and crushing at 50°C, wherein the mass ratio of navel orange pulp, wheat flour, synthetic precursor, KH2PO4 and MgSO4 is 50:60:3:0.2:0.2, the synthetic precursor is composed of sodium selenite and cysteine in a mass ratio of 0.9:1, the composite bacteria for producing glutathione reductase is composed of Pichia pastoris, Streptomyces and Lactobacillus plantarum in an effective live bacteria count of 11:3:2, and the Bacillus producing methionine synthase is Bacillus licheniformis.

[0025] Comparative Example 3 A method for preparing a selenomethionine feed additive comprises the following steps: The navel orange pulp is crushed, passed through a 25mm sieve, and wheat flour, synthetic precursor KH2PO4 and MgSO4 are added and mixed evenly to obtain a fermentation substrate. The moisture content of the fermentation substrate is controlled to be 50%. At a pH of 6, a glutathione reductase-producing yeast is inoculated at an inoculum amount of 10% of the fermentation substrate. The mixture is mixed evenly, the fermentation temperature is controlled at 26°C, and the fermentation is carried out for 15 days. Then, a methionine synthase-producing Bacillus is inoculated at an inoculum amount of 12% of the fermentation substrate. The mixture is fermented for 12 days, dried at a temperature of 50°C, and crushed to obtain a selenomethionine feed additive. The mass ratio of the navel orange pulp, wheat flour, synthetic precursor, KH2PO4 and MgSO4 is 50:60:3:0.2:0.2. The synthetic precursor is composed of sodium selenite and cysteine at a mass ratio of 0.7:1. The glutathione reductase-producing yeast is Pichia pastoris, and the methionine synthase-producing Bacillus is Bacillus licheniformis.

[0026] Comparative Example 4 A method for preparing a selenomethionine feed additive comprises the following steps: The navel orange pulp was crushed and passed through a 25 mm sieve. Wheat flour, synthetic precursors KH2PO4 and MgSO4 were added and mixed evenly to obtain a fermentation substrate. The moisture content of the fermentation substrate was controlled to be 50%. At a pH of 6, a composite strain of glutathione reductase-producing bacteria was inoculated at an inoculum amount of 10% of the fermentation substrate. The mixture was mixed evenly. The fermentation temperature was controlled at 26°C and fermented for 15 days. Then, a Bacillus sp. producing methionine synthase was inoculated at an inoculum amount of 12% of the fermentation substrate and fermented for 12 days. , dried and crushed at a temperature of 50°C to obtain a selenomethionine feed additive, wherein the mass ratio of navel orange pulp, wheat flour, synthetic precursor, KH2PO4 and MgSO4 is 50:60:3:0.2:0.2, the synthetic precursor is composed of sodium selenite and cysteine in a mass ratio of 0.7:1, the composite bacteria producing glutathione reductase is composed of Pichia pastoris and Streptomyces with an effective viable cell count of 11:3, and the Bacillus producing methionine synthase is Bacillus licheniformis.

[0027] Comparative Example 5 A method for preparing a selenomethionine feed additive comprises the following steps: The navel orange pulp was crushed and passed through a 25 mm sieve. Wheat flour, synthetic precursors KH2PO4 and MgSO4 were added and mixed evenly to obtain a fermentation substrate. The moisture content of the fermentation substrate was controlled to be 50%. At a pH of 6, a composite strain of glutathione reductase was inoculated at an inoculum amount of 10% of the fermentation substrate. The mixture was mixed evenly. The fermentation temperature was controlled at 26°C and fermented for 15 days. Then, a Bacillus sp. producing methionine synthase was inoculated at an inoculum amount of 12% of the fermentation substrate and fermented for 12 days. The selenomethionine feed additive is obtained by drying and crushing at a temperature of 50°C, wherein the mass ratio of navel orange pulp, wheat flour, synthetic precursor, KH2PO4 and MgSO4 is 50:60:3:0.2:0.2, the synthetic precursor is composed of sodium selenite and cysteine in a mass ratio of 0.7:1, the composite bacteria for producing glutathione reductase is composed of Pichia pastoris and Lactobacillus plantarum with an effective viable bacterial count of 11:2, and the Bacillus producing methionine synthase is Bacillus licheniformis.

[0028] Comparative Example 6 A method for preparing a selenomethionine feed additive comprises the following steps: The navel orange pulp was crushed and passed through a 25 mm sieve. Wheat flour, synthetic precursors KH2PO4 and MgSO4 were added and mixed evenly to obtain a fermentation substrate. The moisture content of the fermentation substrate was controlled to be 50%. At a pH of 6, a composite strain of glutathione reductase was inoculated at an inoculation rate of 10% of the fermentation substrate. The mixture was mixed evenly. Then, a Bacillus sp. producing methionine synthase was inoculated at an inoculation rate of 12% of the fermentation substrate. The fermentation temperature was controlled at 26°C and fermented for 27 days. The fermentation was continued at a temperature of 50°C. ℃, drying, and crushing to obtain a selenomethionine feed additive, wherein the mass ratio of navel orange pulp, wheat flour, synthetic precursor, KH2PO4 and MgSO4 is 50:60:3:0.2:0.2, the synthetic precursor is composed of sodium selenite and cysteine in a mass ratio of 0.7:1, the composite bacteria for producing glutathione reductase is composed of Pichia pastoris, Streptomyces and Lactobacillus plantarum in an effective viable count of 11:3:2, and the Bacillus producing methionine synthase is Bacillus licheniformis.

[0029] Comparative Example 7 A method for preparing a selenomethionine feed additive comprises the following steps: The navel orange residue was crushed and passed through a 25 mm sieve, and wheat flour, synthetic precursors KH2PO4 and MgSO4 were added and mixed evenly to obtain a fermentation substrate. The moisture content of the fermentation substrate was controlled to be 50%, and the pH was controlled to be 6. The fermentation temperature was controlled to be 26 ° C. First, Bacillus producing methionine synthase was inoculated at an inoculation amount of 12% of the fermentation substrate and fermented for 12 days. Then, a composite strain producing glutathione reductase was inoculated at an inoculation amount of 10% of the fermentation substrate. The mixture was mixed evenly and fermented for 15 days. The selenomethionine feed additive is prepared by drying and crushing at 50°C, wherein the mass ratio of navel orange pulp, wheat flour, synthetic precursor, KH2PO4 and MgSO4 is 50:60:3:0.2:0.2, the synthetic precursor is composed of sodium selenite and cysteine in a mass ratio of 0.7:1, the composite bacteria for producing glutathione reductase is composed of Pichia pastoris, Streptomyces and Lactobacillus plantarum in an effective live bacteria count of 11:3:2, and the Bacillus producing methionine synthase is Bacillus licheniformis.

[0030] Comparative Example 8 A method for preparing a selenomethionine feed additive comprises the following steps: The navel orange pulp was crushed and passed through a 25 mm sieve, and wheat flour, synthetic precursors KH2PO4 and MgSO4 were added and mixed evenly to obtain a fermentation substrate. The moisture content of the fermentation substrate was controlled to be 50%. At a pH of 6, a composite strain of glutathione reductase was inoculated at an inoculation amount of 10% of the fermentation substrate. The mixture was mixed evenly. The fermentation temperature was controlled at 26°C and fermented for 15 days. Then, a Bacillus subtilis producing methionine synthase was inoculated at an inoculation amount of 12% of the fermentation substrate. The fermentation was continued for 12 days. The selenomethionine feed additive is prepared by drying and crushing at 50°C, wherein the mass ratio of navel orange pulp, wheat flour, synthetic precursor, KH2PO4 and MgSO4 is 50:60:3:0.2:0.2, the synthetic precursor is composed of sodium selenite and cysteine in a mass ratio of 0.7:1, the composite bacteria for producing glutathione reductase is composed of Pichia pastoris, Streptomyces and Lactobacillus plantarum in an effective live bacteria count of 11:3:2, and the Bacillus producing methionine synthase is Bacillus licheniformis.

[0031] Performance Testing The present application has found through preliminary experimental research that the ratio of selenomethionine production to total selenium (conversion rate) after fermentation is related to the feed ratio of cysteine and sodium selenite before fermentation, and is positively correlated with selenomethionine production within a certain content range. By controlling other fermentation conditions to be exactly the same, only changing the feed ratio of cysteine and sodium selenite in the synthetic precursor, and measuring the conversion rate of selenomethionine after fermentation. See Table 1 and Figure 1 The feed additive containing selenomethionine is synthesized by biological process such as Figure 2 shown.

[0032] Selenium forms: Speciation separation and quantification were performed using high performance liquid chromatography-atomic fluorescence spectrometry; Determination of total selenium content: Tested in accordance with the industry standard HJ 694-2014 "Water quality - Determination of mercury, arsenic, selenium, bismuth and antimony - Atomic fluorescence method"; Table 1 Conversion rate of selenomethionine after fermentation at different feed ratios of cysteine and sodium selenite

[0033] The various forms of selenium in the selenomethionine feed additives prepared in Examples 1-3 and Comparative Examples 1-8 of the present application were tested respectively. The test results are shown in Table 2.

[0034] Table 2 Test results of selenomethionine feed additives prepared in Examples 1-3 and Comparative Examples 1-8

[0035] As shown in Tables 1-2, the method for preparing a selenomethionine feed additive provided herein not only simplifies production equipment and processes, but also has low environmental requirements. The solid-state fermentation method generates no waste gas, wastewater, or waste residue, making it environmentally friendly and energy-efficient. The preparation method also produces a high organic selenium content, with selenomethionine accounting for over 50% of the total selenium content, reaching a maximum of 73.11%, meeting the standards for feed additives (the standard for imported selenomethionine is over 50%).

[0036] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for preparing a selenomethionine feed additive, characterized in that: The method comprises the following preparation steps: After crushing and sieving the navel orange residue, wheat flour, synthetic precursor, KH2PO4 and MgSO4 are added, and the mixture is evenly mixed to obtain a fermentation substrate. The moisture content of the fermentation substrate is controlled to be 40-65%. At a pH of 4-8, a composite strain of bacteria producing glutathione reductase is inoculated, and the mixture is evenly mixed. The fermentation temperature is controlled to be 20-32°C, and the mixture is fermented for 10-20 days. Then, Bacillus producing methionine synthase is inoculated, and the mixture is fermented for 10-15 days. The mixture is dried at a temperature of 40-65°C, and crushed to obtain a selenomethionine feed additive.

2. The method for preparing the selenomethionine feed additive according to claim 1, wherein The mass ratio of the navel orange pulp, wheat flour, synthetic precursor, KH2PO4 and MgSO4 is 10-80:15-85:0.1-5:0.01-0.5:0.01-0.

5.

3. The preparation method of the selenomethionine feed additive according to claim 1, wherein The synthetic precursor consists of sodium selenite and cysteine in a mass ratio of 0.6-0.8:

1.

4. The method for preparing the selenomethionine feed additive according to claim 3, wherein The synthetic precursor consists of sodium selenite and cysteine in a mass ratio of 0.7:

1.

5. The preparation method of the selenomethionine feed additive according to claim 1, characterized in that, The composite bacterial strain producing glutathione reductase consists of Pichia pastoris, Streptomyces and Lactobacillus plantarum with effective live bacterial counts of 10-12:2-4:1-3.

6. The method for preparing the selenomethionine feed additive according to claim 1, wherein The methionine synthase-producing Bacillus is Bacillus licheniformis and / or Bacillus subtilis.

7. The method for preparing the selenomethionine feed additive according to claim 1, wherein The inoculation amount of the glutathione reductase-producing composite bacterial strain is 5-15% of the fermentation substrate.

8. The method for preparing the selenomethionine feed additive according to claim 1, wherein The inoculation amount of the methionine synthase-producing Bacillus is 8-15% of the fermentation substrate.

9. A selenomethionine feed additive prepared by the preparation method according to claims 1-8.

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