Application of streptomyces in fermenting and hydrolyzing plant raw material containing plant protein

Abstract

The invention discloses application of streptomyces in fermenting and hydrolyzing plant raw materials containing plant proteins. The streptomyces fermented vegetable protein is found for the first time; the streptomyces is used for solid-state fermentation, so that the digestibility of the vegetable protein raw material can be remarkably improved; according to the invention, fermentation conditions and a treatment method are optimized, so that the content of soluble protein in total crude protein is more than 80%. The soluble protein content and animal in-vitro digestibility of the fermented product are greatly improved, and anti-nutritional factors and allergen proteins are comprehensively removed. The technology is expected to be widely applied to the fields of animal feed, health care products, food additives and the like, and a production solution of high-quality protein products is provided.

Description

[0001] The present invention relates to a microbial solid-state fermentation technology, and in particular to the application of Streptomyces in fermenting and hydrolyzing plant materials containing plant proteins. Background Art

[0002] In recent years, the rapid growth of the world's population has led to a massive depletion of protein resources. However, current agricultural production still cannot adequately meet the growing demand for protein resources. Both humans and animals require high-quality protein for survival. Traditional animal proteins, such as pork, chicken, and fish, are nutritionally valuable and can be consumed directly by humans and animals, but they are expensive. Plant protein raw materials, such as soybean meal, rapeseed meal, cottonseed meal, peanut meal, corn meal, and their protein extracts, are rich in protein and inexpensive. They are currently widely used as animal feed to partially replace expensive animal protein. However, plant proteins have a large molecular weight, low solubility, and their cross-linked structure with lignocellulose hinders efficient digestion by animals' natural digestive enzymes. Furthermore, due to the presence of anti-nutritional factors in plant proteins, excessive intake can lead to health problems in animals, further reducing their nutritional value. Therefore, developing a process for preparing plant protein raw materials with high digestibility is of great significance.

[0003] Currently, the main methods for recycling protein components from plant protein raw materials include chemical methods, enzymatic methods, and fermentation methods. Chemical methods use acid-base reagents to extract protein from plant protein raw materials, but the extraction efficiency is low and the cost is high. The extracted protein has a large molecular weight and is not easily digested and utilized by animals. Enzymatic methods use proteases to hydrolyze the protein, and the hydrolyzate is easily absorbed and utilized by animals. However, the enzymatic hydrolysis process is complex and expensive, and the drying time of the hydrolyzate is long. Fermentation is a cleaner, more environmentally friendly, and more cost-effective process than chemical and enzymatic methods. It utilizes microbial strains to produce enzymes that degrade large molecular proteins into soluble peptides and free amino acids, effectively improving the palatability and in vitro digestibility of plant protein. However, fermentation products obtained from plant protein raw material fermentation processes reported in recent years still suffer from low soluble protein recovery, low in vitro digestibility, and low removal of anti-nutritional factors. To address these issues, it is necessary to develop new and efficient fermentation processes to improve the utilization of plant protein raw materials. Summary of the Invention

[0004] The primary purpose of the present invention is to overcome the problems of low soluble protein recovery, low in vitro digestibility, and low anti-nutritional factor removal in existing fermentation processes. It provides for the first time the use of Streptomyces in the fermentation and hydrolysis of plant materials containing plant proteins to produce soluble polypeptides and free amino acids through solid-state fermentation. The second object of the present invention is to provide a fermentation product obtained through the above application.

[0005] The third object of the present invention is to provide applications of the above fermentation product.

[0006] The purpose of the present invention is achieved through the following technical solutions: Application of Streptomyces in fermentation and hydrolysis of plant materials containing plant protein.

[0007] Furthermore, the Streptomyces includes at least one of Streptomyces SCUT-1, Streptomyces SCUT-3940 and Streptomyces thermophilus CGMCC4.1901.

[0008] Furthermore, the fermentation is solid-state fermentation.

[0009] Furthermore, the fermentation is performed at 35-45° C. for 2-5 days.

[0010] Furthermore, the crude protein content in the plant raw material containing plant protein is above 30%.

[0011] Furthermore, the plant raw material containing plant protein includes at least one of soybean meal, soy protein, cottonseed meal, cottonseed protein, rapeseed meal, peanut meal, distillers dried grains (DDGS) and corn protein.

[0012] Furthermore, the application includes the following steps: Streptomyces is inoculated into a solid fermentation matrix containing plant raw materials and fermented to obtain a fermentation product.

[0013] Furthermore, the Streptomyces is at a concentration of 7≤OD 600 ≤10 Streptomyces liquid; the inoculation amount of the Streptomyces liquid is 2% to 10% of the mass of the solid-state fermentation substrate; further, the inoculation amount of the Streptomyces liquid is 5% of the mass of the solid-state fermentation substrate.

[0014] Furthermore, the preparation of the solid-state fermentation matrix containing plant raw materials comprises the following steps: The plant material is mixed with a salt solution and heated; Still further, the salt solution contains 0.2-0.6 g / L KH2PO4, 0.4-0.8 g / L K2HPO4, 0.3-0.7 g / L MgSO4, and 0.01-0.03 g / L FeSO4; still further, the salt solution contains 0.4 g / L KH2PO4, 0.6 g / L K2HPO4, 0.5 g / L MgSO4, and 0.02 g / L FeSO4; Still further, the solvent of the salt solution is water; Furthermore, the mass volume ratio of the plant material to the salt solution is (2-1):(1-2); Furthermore, the heating is heating to 100-121° C. for 10-30 min; and further still, the heating is heating to 100° C. for 20 min.

[0015] A fermentation product is obtained through the above application.

[0016] Application of the fermentation product in preparing feed, food additives, agricultural ecological fertilizers or cosmetic additives.

[0017] The present invention has the following advantages and effects compared to the prior art: This invention is the first to discover the fermentation of plant protein using Streptomyces. Using Streptomyces for solid-state fermentation, this invention significantly improves the digestibility and absorption rate of plant protein raw materials. By optimizing fermentation conditions and processing methods, this invention achieves a soluble protein content exceeding 80% of the total crude protein, reaching world-leading levels.

[0018] The application of Streptomyces in the fermentation and hydrolysis of plant-based protein-containing raw materials has significantly increased the soluble protein content and in vitro digestibility of the fermented products, while also completely removing anti-nutritional factors and allergens. This technology is expected to be widely used in animal feed, health supplements, and food additives, providing solutions for the production of high-quality protein products. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the solid-state fermentation of the present invention. DETAILED DESCRIPTION

[0020] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0021] The schematic diagram of solid-state fermentation in the embodiment is as follows Figure 1 shown.

[0022] The strains used in the examples: Streptomyces ( Streptomyce sp.) SCUT-1 has been disclosed in the patent publication "CN110317748A A Streptomyces strain and its application in feather degradation", with a deposit number of GDMCC No: 60612; Streptomyces ( Streptomyce sp.) SCUT-3940 is the recombinant strain SCUT-Osep39-Osep40 constructed in Example 1 disclosed in the patent publication "CN115927332A A promoter for overexpressing protease, Streptomyces recombinant bacteria, and construction method and application thereof", and is now renamed Streptomyces ( Streptomycesp.) SCUT-3940; Streptomyces thermolineatus CGMCC4.1901 can be purchased from the China General Microbiological Culture Collection Center.

[0023] The soybean meal in Example 1 was purchased from Wen's Food Group Co., Ltd.; the soybean protein in Example 2 was purchased from Wen's Food Group Co., Ltd.; the cottonseed meal in Example 3 was purchased from Shijiazhuang Jiahui Feed Co., Ltd.; the cottonseed protein in Example 4 was purchased from Foshan Jieda Feed Co., Ltd.; the rapeseed meal in Example 5 was purchased from Foshan Jieda Feed Co., Ltd.; the peanut meal in Example 6 was purchased from Jida Peanut Oil Mill in Maoming Binhai New Area; the corn distiller's grains in Example 7 was purchased from Shijiazhuang Jiahui Feed Co., Ltd.; and the corn protein in Example 8 was purchased from Foshan Jieda Feed Co., Ltd.

[0024] The detection of various indicators in the embodiment is as follows: (1) Crude protein content: The protein content in the sample was determined according to the Kjeldahl method in accordance with GB / T 6432-2018.

[0025] (2) Soluble crude protein content: the sample to be tested was mixed with distilled water at a ratio of 1:25, and the mixture was shaken and extracted in a shaker at 37 °C for 2 h. After centrifugation at 10,000 × g for 10 min, the supernatant was collected to obtain the soluble components in the sample, and the protein content was determined according to the Kjeldahl method according to GB / T 6432-2018.

[0026] (3) Soluble polypeptides were determined using TaKaRa's BCA protein detection kit.

[0027] (4) Free amino acids: 2.00 g of the fermentation product obtained in the example was added to a 100 mL distilled water shaker and shaken for 1 hour. The supernatant was collected by centrifugation and the amino acid content was determined using an amino acid analyzer (the free amino acids in the supernatant were separated by an ion exchange column and then reacted with a ninhydrin solution to produce a color reaction, and the amino acid content was then determined using a visible light spectrophotometer).

[0028] (5) Amino acid nitrogen: The amino acid nitrogen in the sample was determined according to the method in GB 5009.235-2016 “National Food Safety Standard - Determination of Amino Acid Nitrogen in Food”.

[0029] (6) Soybean allergens were determined using colloidal gold antigen-antibody test cards. The test cards were purchased from IVDBIO (Huzhou, China). The allergens in the samples were extracted with extraction solution and tested according to the test card method.

[0030] (7) Free gossypol content: Preparation of isopropanol-n-hexane mixed solution: Mix 60 mL of isopropanol with 40 mL of n-hexane and store at 4°C until use. Preparation of solvent A: Add 25 mL of isopropanol-n-hexane mixed solution, 100 μL of 3-amino-1-propanol, 400 μL of glacial acetic acid, and 2.5 mL of ultrapure water to a 50 mL volumetric flask, then dilute to the 50 mL mark with isopropanol-n-hexane mixed solution, shake well, and store at 4°C until use. Take 2 g of dried sample to be tested, add 20 mL of solvent A, shake and extract for 2 h, centrifuge at 12000×g for 5 min, take the supernatant, filter through a 0.22 μm organic filter membrane, and obtain the HPLC test solution. HPLC reference conditions: Chromatographic column: C18 column, 250 mm×4.6 mm, 5 μm. Mobile phase: methanol: phosphoric acid solution = 85:15 (v / v). Flow rate: 1.0 mL / min. Column temperature: 40℃±1℃. Detection wavelength: 235 nm. Injection volume: 10 μL. 30 H 30 O8) The standard sample is used as a reference to draw a standard curve to obtain the free gossypol content of the sample to be tested.

[0031] (8) Glucosinolate content: The content of glucosinolate was determined using the Bioesn glucosinolate content detection kit.

[0032] (9) Phytic acid content: The content was determined using Macklin's phytic acid detection kit.

[0033] (10) In vitro digestibility: The in vitro digestibility of the sample was determined according to the method in GB / T 17811-2008 “Determination of pepsin digestibility of animal protein feeds - filtration method”.

[0034] Example 1 Solid-state fermentation of soybean meal Soybean meal (containing 43.6% crude protein by mass) was mixed with a basal salt solution (containing 0.4 g / L KH2PO4, 0.6 g / L K2HPO4, 0.5 g / L MgSO4, and 0.02 g / L FeSO4; the solvent was ddH2O) at a ratio of 1 g:1 mL and pretreated at 100°C for 20 minutes to obtain a solid-state fermentation substrate. Spores of Streptomyces SCUT-1, Streptomyces SCUT-3940, or Streptomyces thermophilus CGMCC4.1901 were scraped and inoculated into LB medium. The culture was incubated for 24 hours to obtain a bacterial solution concentration of 7 ≤ OD 600≤10 seed liquid. 5% of the seed liquid mass of the solid fermentation matrix was inoculated into the solid fermentation matrix, stirred evenly, and spread evenly on a shallow plate. The fermentation was allowed to stand at 40°C for 3 days, and then dried to obtain fermented soybean meal. The crude protein content, soluble crude protein percentage, soluble polypeptide percentage, free amino acid percentage, amino acid nitrogen content, soybean allergen removal effect, and in vitro digestibility before and after fermentation of the fermented soybean meal are shown in Table 1: Table 1 Various indicators of fermented soybean meal (content and proportion in the table are all mass percentages)

[0035] The prior art (Teng, Da, et al. "Bio-modification of soybean meal with Bacillus subtilis or Aspergillus oryzae." Biocatalysis and Agricultural Biotechnology 1.1 (2012): 32-38.) discloses that soybean meal was fermented with Bacillus subtilis BS102 at a material-liquid ratio of 1 g:2 mL for 72 h, resulting in a fermentation product with a soluble crude protein content of 32.98%.

[0036] The prior art (Zheng, L., et al. "Effects of Bacillus fermentation on the protein microstructure and anti-nutritional factors of soybean meal." Letters in Applied Microbiology 65.6 (2017): 520-526.) discloses that soybean meal was fermented with siam Bacillus JL8 at a material-liquid ratio of 1 g:2 mL for 24 h, resulting in a fermentation product with a soluble crude protein content of 10.91%.

[0037] Streptomyces SCUT-1, SCUT-3940, and thermoline CGMCC4.1901 are capable of recovering soluble protein from plant protein fermentation. Fermented soybean meal obtained by SCUT-1, SCUT-3940, and thermoline CGMCC4.1901 at a feed-liquid ratio of 1 g:1 mL for 72 hours had soluble crude protein contents of 25.5%, 41.6%, and 17.1%, respectively. These results are comparable to, and some even surpass, existing strains known to ferment plant protein.

[0038] Example 2 Solid-state fermentation of soybean protein Soy protein (83.1% crude protein by mass) was mixed with a basic salt solution (containing 0.4 g / L KH2PO4, 0.6 g / L K2HPO4, 0.5 g / L MgSO4, and 0.02 g / L FeSO4; the solvent was ddH2O) at a ratio of 1 g:1 mL and pretreated at 100°C for 20 minutes to obtain a solid-state fermentation substrate. Spores of Streptomyces SCUT-1, Streptomyces SCUT-3940, or Streptomyces thermophilus CGMCC4.1901 were scraped and inoculated into LB medium. The culture was cultured for 24 hours to obtain a bacterial solution concentration of 7 ≤ OD 600 ≤10 seed liquid. The seed liquid was inoculated into the solid fermentation matrix at a ratio of 5% of the mass of the solid fermentation matrix, stirred evenly, and spread on a shallow plate. The fermentation was allowed to stand at 40°C for 3 days, and then dried to obtain fermented soy protein. The crude protein content, soluble crude protein percentage, soluble polypeptide percentage, free amino acid percentage, amino acid nitrogen content, soybean allergen removal effect, and in vitro digestibility before and after fermentation of the fermented soy protein are shown in Table 2: Table 2 Various indicators of fermented soybean protein (content and proportion in the table are all mass percentages)

[0039] Example 3 Solid-state fermentation of cottonseed meal Cottonseed meal (containing 45.6% protein by mass) was mixed with a basic salt solution (containing 0.4 g / L KH2PO4, 0.6 g / L K2HPO4, 0.5 g / L MgSO4, and 0.02 g / L FeSO4; the solvent was ddH2O) at a ratio of 1 g:1.5 mL and pretreated at 100°C for 20 minutes to obtain a solid-state fermentation substrate. Spores of Streptomyces SCUT-1, Streptomyces SCUT-3940, or Streptomyces thermophilus CGMCC4.1901 were scraped and inoculated into LB medium. The culture was cultured for 24 hours to obtain a bacterial solution concentration of 7 ≤ OD 600 ≤10 seed liquid. The seed liquid was inoculated into the solid fermentation matrix at a ratio of 5% of the mass of the solid fermentation matrix, stirred evenly, and spread flat on a shallow plate. The fermentation was allowed to stand at 40°C for 3 days, and then dried to obtain fermented cottonseed meal. The crude protein content, soluble crude protein percentage, soluble polypeptide percentage, free amino acid percentage, free gossypol content before and after fermentation, and in vitro digestibility before and after fermentation of the fermented cottonseed meal are shown in Table 3: Table 3 Various indicators of fermented cottonseed meal (the content and proportion in the table are all mass percentages)

[0040] The prior art (Li, Jia, et al. "Anaerobic solid-state fermentation with Bacillus subtilis for digestingfree gossypol and improving nutritional quality in cottonseed meal." Frontiers in nutrition 9 (2022): 1017637.) discloses that Bacillus subtilis M-15 fermented cottonseed meal at a solid-liquid ratio of 1 g:1 mL for 14 days, obtaining a soluble crude protein content of 13.26% in the fermentation product.

[0041] It was shown that Streptomyces SCUT-1, Streptomyces SCUT-3940, and Streptomyces thermophilus CGMCC4.1901 are capable of recovering soluble protein from plant protein fermentation. The soluble crude protein contents of cottonseed meal fermented for 72 h with Streptomyces SCUT-1, Streptomyces SCUT-3940, and Streptomyces thermophilus CGMCC4.1901 at a solid-liquid ratio of 1 g:1.5 mL were 28.2%, 42.7%, and 20.2%, respectively. The ability of Streptomyces SCUT-1, Streptomyces SCUT-3940, and Streptomyces thermophilus CGMCC4.1901 to recover soluble crude protein from cottonseed meal surpasses that of existing strains known to ferment plant protein.

[0042] Example 4 Solid-state fermentation of cottonseed protein Cottonseed protein (61.8% crude protein by mass) was mixed with a basic salt solution (containing 0.4 g / L KH2PO4, 0.6 g / L K2HPO4, 0.5 g / L MgSO4, and 0.02 g / L FeSO4; the solvent was ddH2O) at a ratio of 1 g:1.5 mL and pretreated at 100°C for 20 minutes to obtain a solid-state fermentation substrate. Spores of Streptomyces SCUT-1, Streptomyces SCUT-3940, or Streptomyces thermophilus CGMCC4.1901 were scraped and inoculated into LB medium. The culture was cultured for 24 hours to obtain a bacterial solution concentration of 7 ≤ OD 600 ≤10 seed liquid. The seed liquid was inoculated into the solid fermentation matrix at a ratio of 5% of the mass of the solid fermentation matrix, stirred evenly, and spread on a shallow plate. The fermentation was allowed to stand at 40°C for 3 days, and then dried to obtain fermented cottonseed protein. The crude protein content, soluble crude protein percentage, soluble polypeptide percentage, free amino acid percentage, free gossypol content before and after fermentation, and in vitro digestibility before and after fermentation of the fermented cottonseed protein are shown in Table 4: Table 4 Various indicators of fermented cottonseed protein (the content and proportion in the table are all mass percentages)

[0043] Example 5 Solid-state fermentation of rapeseed meal Rapeseed meal (containing 40.3% crude protein by mass) was mixed with a basic salt solution (containing 0.4 g / L KH2PO4, 0.6 g / L K2HPO4, 0.5 g / L MgSO4, and 0.02 g / L FeSO4; the solvent was ddH2O) at a ratio of 1 g:2 mL and pretreated at 100°C for 20 minutes to obtain a solid-state fermentation substrate. Spores of Streptomyces SCUT-1, Streptomyces SCUT-3940, or Streptomyces thermophilus CGMCC4.1901 were scraped and inoculated into LB medium. The culture was cultured for 24 hours to obtain a bacterial solution concentration of 7 ≤ OD 600 ≤10 seed liquid. The seed liquid was inoculated into the solid fermentation matrix at a ratio of 5% of the mass of the solid fermentation matrix, stirred evenly, and spread evenly on a shallow plate. The fermentation was allowed to stand at 40°C for 2 days, and then dried to obtain the fermented rapeseed meal. The crude protein content, soluble crude protein percentage, soluble polypeptide percentage, free amino acid percentage, glucosinolate content before and after fermentation, and in vitro digestibility before and after fermentation of the fermented rapeseed meal are shown in Table 5: Table 5 Various indicators of fermented rapeseed meal (content and proportion in the table are all mass percentages)

[0044] The prior art (Shi, Changyou, et al. "Solid state fermentation of rapeseed cake with Aspergillus niger fordegrading glucosinolates and upgrading nutritional value." Journal of animal science and biotechnology 6 (2015): 1-7.) discloses that Aspergillus niger CICC41258 fermented rapeseed meal at a solid-liquid ratio of 1 g:1.5 mL for 48 h, resulting in a fermentation product with a soluble crude protein content of 12.48%.

[0045] Prior art (Jin, Hu, et al. "Direct bio-utilization of untreated rapeseed meal for effective iturin A production by Bacillus subtilis insubmerged fermentation." Plos one 9.10 (2014): e111171. ) discloses fermenting rapeseed meal with Bacillus subtilis 3-10 at a material-liquid ratio of 1 g:11 mL for 72 h, resulting in a fermentation product with a soluble crude protein content of 4.5%.

[0046] It was shown that Streptomyces SCUT-1, Streptomyces SCUT-3940, and Streptomyces thermophilus CGMCC4.1901 are capable of recovering soluble protein from plant protein fermentation. The soluble crude protein contents of rapeseed meal fermented for 48 h with Streptomyces SCUT-1, Streptomyces SCUT-3940, and Streptomyces thermophilus CGMCC4.1901 at a solid-liquid ratio of 1 g:2 mL were 23.7%, 35.3%, and 22.1%, respectively. The ability of Streptomyces SCUT-1, Streptomyces SCUT-3940, and Streptomyces thermophilus CGMCC4.1901 to recover soluble crude protein from rapeseed meal surpasses that of existing strains known to ferment plant protein.

[0047] Example 6 Solid-state fermentation of peanut meal Peanut meal (containing 53.4% ​​crude protein by mass) was mixed with a basic salt solution (containing 0.4 g / L KH2PO4, 0.6 g / L K2HPO4, 0.5 g / L MgSO4, and 0.02 g / L FeSO4; the solvent was ddH2O) at a ratio of 1 g:1.5 mL and pretreated at 100°C for 20 minutes to obtain a solid-state fermentation substrate. Spores of Streptomyces SCUT-1, Streptomyces SCUT-3940, or Streptomyces thermophilus CGMCC4.1901 were scraped and inoculated into LB medium. The culture was cultured for 24 hours to obtain a bacterial solution concentration of 7 ≤ OD 600 ≤10 seed liquid. The seed liquid was inoculated into the solid fermentation matrix at a ratio of 5% of the mass of the solid fermentation matrix, stirred evenly, and spread on a shallow plate. It was allowed to ferment at 40°C for 2 days and dried to obtain fermented peanut meal. The crude protein content, soluble crude protein percentage, soluble polypeptide percentage, free amino acid percentage, phytic acid content before and after fermentation, and in vitro digestibility before and after fermentation of the fermented peanut meal are shown in Table 6: Table 6 Various indicators of fermented peanut meal (content and proportion in the table are all mass percentages)

[0048] The existing technology (Xu Huiru, Chu Lijun, Li Qiu, et al. Industrial production and quality analysis of peanut meal by solid-state fermentation [J]. Grain and Food Industry, 2015, 22(6):41-43.DOI:10.3969 / j.issn.1672-5026.2015.06.010) discloses that peanut meal is fermented with a mixture of yeast, lactic acid bacteria, Bacillus and other strains at a material-liquid ratio of 55 g:45 mL for 2 days, and the soluble crude protein content in the fermentation product is 12.45%.

[0049] These results indicate that Streptomyces SCUT-1, SCUT-3940, and thermoline CGMCC4.1901 are capable of recovering soluble protein from plant protein fermentation. Fermentation of peanut meal with Streptomyces SCUT-1, SCUT-3940, and thermoline CGMCC4.1901 at a solid-liquid ratio of 1 g:1.5 mL for 48 h yielded soluble crude protein contents of 37.1%, 48.1%, and 31.8%, respectively. Streptomyces SCUT-1, SCUT-3940, and thermoline CGMCC4.1901 exhibit superior soluble crude protein recovery from peanut meal compared to currently known strains capable of fermenting plant protein.

[0050] Example 7 Solid-state fermentation of corn distiller's grains Corn distiller's grains (containing 29.1% crude protein by mass) were mixed with a basic salt solution (containing 0.4 g / L KH2PO4, 0.6 g / L K2HPO4, 0.5 g / L MgSO4, and 0.02 g / L FeSO4 in ddH2O) at a ratio of 1 g:1.5 mL and pretreated at 121°C for 20 minutes to obtain a solid-state fermentation substrate. Spores of Streptomyces SCUT-1, Streptomyces SCUT-3940, or Streptomyces thermophilus CGMCC4.1901 were scraped and inoculated into LB medium. The culture was incubated for 24 hours to obtain a bacterial solution concentration of 7 ≤ OD 600 ≤10 seed liquid. The seed liquid was inoculated into the solid fermentation matrix at a ratio of 10% of the mass of the solid fermentation matrix, stirred evenly, and spread evenly on a shallow plate. The fermentation was allowed to stand at 40°C for 3 days, and then dried to obtain fermented corn distiller's grains. The crude protein content, soluble crude protein percentage, soluble polypeptide percentage, free amino acid percentage, and in vitro digestibility of the fermented corn distiller's grains before and after fermentation are shown in Table 7: Table 7 Various indicators of fermented corn distiller's grains (content and proportion in the table are all mass percentages)

[0051] Example 8 Solid-state fermentation of zein Corn protein (containing 53.3% crude protein by mass) was mixed with a basic salt solution (containing 0.4 g / L KH2PO4, 0.6 g / L K2HPO4, 0.5 g / L MgSO4, and 0.02 g / L FeSO4; the solvent was ddH2O) at a ratio of 1 g:1.5 mL and pretreated at 121°C for 20 minutes to obtain a solid-state fermentation substrate. Spores of Streptomyces SCUT-1, Streptomyces SCUT-3940, or Streptomyces thermophilus CGMCC4.1901 were scraped and inoculated into LB medium. The culture was cultured for 24 hours to obtain a bacterial solution concentration of 7 ≤ OD 600 ≤10 seed liquid. The seed liquid was inoculated into the solid fermentation matrix at a ratio of 10% of the mass of the solid fermentation matrix, stirred evenly, and spread evenly on a shallow plate. The fermentation was allowed to stand at 40°C for 3 days, and then dried to obtain fermented corn protein. The crude protein content, soluble crude protein percentage, soluble polypeptide percentage, free amino acid percentage, and in vitro digestibility of the fermented corn protein before and after fermentation are shown in Table 8: Table 8 Various indicators of fermented corn protein

[0052] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. Application of Streptomyces in the fermentation and hydrolysis of plant materials containing plant protein.

2. The use according to claim 1, characterized in that The Streptomyces includes at least one of Streptomyces SCUT-1, Streptomyces SCUT-3940 and Streptomyces thermophilus CGMCC4.1901; The fermentation is solid-state fermentation.

3. The use according to claim 1, characterized in that The crude protein content in the plant raw material containing plant protein is more than 30%.

4. The use according to claim 1, characterized in that The plant raw material containing plant protein includes at least one of soybean meal, soybean protein, cottonseed meal, cottonseed protein, rapeseed meal, peanut meal, corn distiller's grains and corn protein.

5. The use according to claim 1, characterized in that The fermentation is carried out by standing and fermenting at 35-45° C. for 2-5 days.

6. The use according to any one of claims 1 to 5, characterized in that: The application comprises the following steps: Streptomyces is inoculated into a solid fermentation matrix containing plant raw materials and fermented to obtain a fermentation product.

7. The use according to claim 6, characterized in that The Streptomyces is at a concentration of 7≤OD 600 ≤10 Streptomyces liquid; the inoculation amount of Streptomyces liquid is 2% to 10% of the mass of the solid-state fermentation substrate.

8. The use according to claim 6, characterized in that The preparation of the solid-state fermentation matrix containing plant raw materials comprises the following steps: The plant material is mixed with the salt solution and heated.

9. The use according to claim 8, characterized in that The salt solution contains 0.2-0.6 g / L KH2PO4, 0.4-0.8 g / L K2HPO4, 0.3-0.7 g / L MgSO4 and 0.01-0.03 g / L FeSO4; The mass volume ratio of the plant material to the salt solution is (2-1): (1-2); The heating is heating to 100-121° C. for 10-30 min; further, the heating is heating to 100° C. for 20 min.

10. Use of the fermentation product according to any one of claims 6 to 9 in preparing feed, food additives, agricultural ecological fertilizers or cosmetic additives.

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