Composite yeast culture and application thereof

Abstract

The present invention discloses a composite yeast culture and its application. The yeast in the composite yeast culture is Saccharomyces cerevisiae strains numbered GCC-1 and GCC-2. Adding the composite yeast culture product to the feed of carp can improve the intestinal and liver health, enhance antioxidant capacity, and have antiviral effects.

Description

Technical Field

[0001] The present invention relates to the field of microorganisms, in particular to a composite yeast culture and application thereof. Background Art

[0002] Yeast culture is a microbial product formed by the complete fermentation of yeast on a culture medium through a specific process. It consists of a certain number of living cells, a large number of metabolites, and a fermentation medium. In recent years, further research has been conducted on the composition and functions of yeast culture. This research has shown that yeast culture has nutritional and nutritional regulatory effects. As a feed additive for aquatic animals, it can enrich the nutritional structure, optimize the intestinal environment of fish, and enhance immunity.

[0003] Aquatic viruses are common diseases in aquaculture. They are numerous and occur across a wide range of water temperatures, and effective treatments are often lacking. Consequently, viral outbreaks often go untreated, resulting in significant economic losses. Existing research has shown that adding yeast culture as a biological agent to aquatic animal feed can, to a certain extent, improve immune function and stress resistance, enhancing aquatic animals' resistance to viruses.

[0004] Due to the distinct characteristics of different yeast strains, different metabolic products such as alcohols, fats, acids, proteins, and minerals are produced during yeast cultivation, as well as some unknown growth factors with specific properties. Currently, different yeasts have limited effects, and research, development, and utilization of synergistic effects among multiple yeasts is lacking. The present invention utilizes two highly active yeast strains screened for growth performance, antiviral capacity, and antioxidant capacity. Through a scientific fermentation process, the yeast culture is produced, which has the potential for practical application and exhibits antioxidant and antiviral effects on fish liver and intestine health. Summary of the Invention

[0005] The purpose of the present invention is to provide a composite yeast culture which can improve the intestinal tract and liver health of carp, enhance the antioxidant capacity and has antiviral effect.

[0006] The present invention provides a yeast, wherein the yeast is Saccharomyces cerevisiae, the strain number of which is GCC-1, and the registration number of which in the China Culture Collection Center for General Microorganisms is CGMCC No. 21819; or the strain number of which is GCC-2, and the registration number of which in the China Culture Collection Center for General Microorganisms is CGMCC No. 21818.

[0007] The present invention provides a bacterial agent, which contains the brewer's yeast and / or a metabolite of the brewer's yeast; the brewer's yeast includes at least one of a brewer's yeast with a strain number of GCC-1 and a brewer's yeast with a strain number of GCC-2.

[0008] The active ingredient of the bacterial agent may be the brewer's yeast or a metabolite of the brewer's yeast. The active ingredient of the bacterial agent may also contain other biological components or carriers of non-biological components of the bacterial agent.

[0009] The metabolites of Saccharomyces cerevisiae refer to a mixture comprising Saccharomyces cerevisiae, culture solution and intermediate products produced during the cultivation of Saccharomyces cerevisiae.

[0010] The ratio of the inoculation amount of the Saccharomyces cerevisiae strain numbered GCC-1 to that of the Saccharomyces cerevisiae strain numbered GCC-2 in the bacterial agent is 1:1.

[0011] The use of the above yeast or the above bacterial agent in the preparation of aquatic feed additives or aquatic feed should also be within the scope of protection of the present invention.

[0012] The present invention provides an aquatic feed additive, which contains the yeast or the bacterial agent according to any one of claims 2-3.

[0013] The present invention provides an aquatic feed, which contains the yeast or the bacterial agent according to any one of claims 2 to 3 or the aquatic feed additive.

[0014] Wherein, the addition amount of the yeast according to claim 1 in the feed is 2×10 10 cells / kg.

[0015] The use of the above yeast, the above bacterial agent, the above aquatic feed additive or the above aquatic feed in any of the following applications shall also fall within the scope of protection of the present invention:

[0016] 1) Improve liver health of aquatic products;

[0017] 2) Improve the intestinal barrier function of aquatic products;

[0018] 3) Enhance the anti-inflammatory ability of aquatic products;

[0019] 4) Improve the antiviral ability of aquatic products.

[0020] Wherein, the aquatic product is fish, and the aquatic feed is fish feed.

[0021] Wherein, the aquatic product is carp, and the aquatic feed is carp feed.

[0022] The present invention provides a composite yeast culture product that, when added to carp feed, can improve intestinal and liver health, enhance antioxidant capacity, and exhibit antiviral effects. Using carp as an example, the product can theoretically be widely used as a feed additive in functional fish feeds.

[0023] Preservation Instructions

[0024] Biomaterials 1

[0025] Classification and nomenclature of biological materials: Saccharomyces cerevisiae

[0026] Strain number of biological material: GCC-1

[0027] Name of the depository of biological materials: China General Microbiology Center of Culture Collection of Microorganisms

[0028] Abbreviation of the depository of biological materials: CGMCC

[0029] The depository address of the biological materials is: Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, China 100101

[0030] Deposit date of biological material: March 9, 2021

[0031] Biomaterials Collection Center Registration Number: CGMCC No.21819

[0032] Biomaterials 2

[0033] Classification and nomenclature of biological materials: Saccharomyces cerevisiae

[0034] Strain number of biological material: GCC-2

[0035] Name of the depository of biological materials: China General Microbiology Center of Culture Collection of Microorganisms

[0036] Abbreviation of the depository of biological materials: CGMCC

[0037] The depository address of the biological materials is: Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, China 100101

[0038] Deposit date of biological material: March 9, 2021

[0039] Biomaterials Collection Center Registration Number: CGMCC No.21818 BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 are ecological parameters.

[0041] Figure 2 is the liver triglyceride (TAG) content.

[0042] Figure 3 Serum alanine aminotransferase (ALT) / aspartate aminotransferase (AST) levels.

[0043] Figure 4 The expression of genes related to liver inflammation (n=6).

[0044] Figure 5 The total antioxidant capacity of the intestine (T-AOC) and superoxide dismutase (SOD) were measured.

[0045] Figure 6 Serum lipopolysaccharide (LPS) and diamine oxidase activity (DAO).

[0046] Figure 7 is the renal SVCV viral load. DETAILED DESCRIPTION

[0047] The present invention will be further described in detail below in conjunction with specific embodiments. The examples provided are only for illustrating the present invention and are not intended to limit the scope of the present invention. The examples provided below can serve as a guide for further improvements by those skilled in the art and are not intended to limit the present invention in any way.

[0048] Unless otherwise specified, the experimental methods in the following examples are conventional methods and were performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials and reagents used in the following examples, unless otherwise specified, were all commercially available.

[0049] The yeast GCC-1 used in the following examples was isolated from shrimp aquaculture pond sludge in the laboratory, and its CGMCC strain deposit number is 21819; the yeast GCC-2 used was isolated from shrimp aquaculture pond sludge in the laboratory, and its CGMCC strain deposit number is 21818.

[0050] The YPD solid medium used in the following experiments consisted of 1% yeast extract, 2% peptone, 2% glucose, 1.6% agar powder, and the remainder water. YPD medium also consisted of 1% yeast extract, 2% peptone, 2% glucose, and the remainder water. Solid fermentation medium consisted of 30% soybean meal, 30% bran, and 40% corn gluten meal as an insoluble solid medium. 4% glucose, 0.5% urea, 0.05% magnesium sulfate, 0.05% potassium dihydrogen phosphate, and 0.01% biotin were weighed, based on the percentage by mass of the solid medium, and dissolved in water (20% by mass of the solid fermentation feedstock). This solution was mixed with the solid fermentation feedstock and then supplemented with a 10× urea solution and a 10× biotin solution sterilized by filtration through a 0.22 μm filter. Enrichment medium consisted of 2% glucose, 2% peptone, 1% yeast extract, 0.01% penicillin, and the remainder was water. Isolation medium: Wash and peel the potatoes, weigh 200 g, cut into small pieces, add water and boil until soft, filter through eight layers of gauze, heat, add 20 g agar, wait until the agar is dissolved, add 20 g glucose, stir thoroughly, cool slightly and then dilute to 1000 mL, dispense into conical flasks, and sterilize at 115°C and high temperature and high pressure for 30 min.

[0051] Example 1. Discovery, Isolation and Purification of Yeast

[0052] 1. Isolation and Purification of Saccharomyces cerevisiae GCC-1 and GCC-2

[0053] (1) Take 5-15cm bottom sludge from shrimp culture pond, take 0.5g and add it to enrichment medium, culture at 28℃ for 2 days; dilute the enrichment solution to 10 -5 , take 100 μL of the dilution and spread it on the separation medium, and culture it at 28°C; pick a single clone according to the colony morphology, use YPD medium at 28°C, 200 r / min for 48 hours to obtain a single colony, which was named GCC-1.

[0054] (2) Select healthy Litopenaeus vannamei and rinse the shrimp surface with sterile 0.85% NaCI solution. After disinfecting the shrimp surface with 75% alcohol, remove the intestine from the dorsal side, and then add sterile saline to the glass homogenizer for homogenization. The homogenized sample was diluted 100 times, and 100 μL of the diluted tissue fluid was evenly spread on the YPD culture medium with a pipette, and then inverted in a constant temperature incubator and cultured at 28°C for 48-96 hours. Single clones were picked according to the colony morphology and cultured using YPD culture medium at 28°C and 200 r / min for 48 hours to obtain a single colony, named GCC-2.

[0055] 2. Identification of Saccharomyces cerevisiae GCC-1 and GCC-2

[0056] (1) Morphological identification

[0057] Select the bacterial strain, streak it on YPD medium, culture it at 30℃ for 48h, and observe the colony morphology;

[0058] Morphological identification results: GCC-1 colonies are approximately 1-2 mm in size, with a uniform milky white color, neat edges, and a moist, smooth surface that is easy to pick up. GCC-2 colonies are approximately 1 mm in size, with a uniform white color, neat edges, and a moist, smooth surface that is easy to pick up.

[0059] (2) Molecular identification

[0060] The strain sequencing was completed by Beijing Ruibo Xingke Company, and the gene tested was 16S rDNA; the sequencing results of 16S rDNA of GCC-1 are shown in Sequence 1; the sequencing results of 16S rDNA of GCC-2 are shown in Sequence 2. After comparison with NCBI blast (https: / / blast.ncbi.nlm.nih.gov / Blast.cgi), GCC-1 and GCC-2 belong to Saccharomyces cerevisiae.

[0061] 3. Deposit of Saccharomyces cerevisiae GCC-1 and GCC-2

[0062] Saccharomyces cerevisiae GCC-1 was deposited with the China General Microorganisms Center (CGMCC) on March 9, 2021, with the accession number CGMCC No. 21819. Saccharomyces cerevisiae GCC-1 is referred to as Saccharomyces cerevisiae GCC-1. Saccharomyces cerevisiae GCC-2 was deposited with the China General Microorganisms Center (CGMCC) on March 9, 2021, with the accession number CGMCC No. 21818. Saccharomyces cerevisiae GCC-2 is referred to as Saccharomyces cerevisiae GCC-2.

[0063] Example 2: Preparation of solid fermentation medium for Saccharomyces cerevisiae

[0064] 1. Cultivation of Saccharomyces cerevisiae GCC-1

[0065] 1) Activation of bacterial strains: Saccharomyces cerevisiae GCC-1 in Example 1 was streaked onto YPD solid plates and cultured at 30° C. for 48 h.

[0066] 2) Primary seed solution culture: Single colonies of the activated Saccharomyces cerevisiae GCC-1 in step 1) were picked and placed in YPD medium, and cultured at 30° C. and 180 rpm for 48 h to obtain a primary seed solution of Saccharomyces cerevisiae GCC-1.

[0067] 3) Secondary seed solution culture: The primary seed solution of Saccharomyces cerevisiae GCC-1 was transferred to fresh YPD medium at a 1% inoculum rate and cultured at 30°C and 180 rpm for 24 h to obtain the secondary seed solution of Saccharomyces cerevisiae GCC-1.

[0068] 2. Cultivation of Saccharomyces cerevisiae GCC-2

[0069] 1) Activation of bacterial strains: Saccharomyces cerevisiae GCC-2 in Example 1 was streaked onto YPD solid plates and cultured at 30° C. for 48 h.

[0070] 2) Primary seed solution culture: Single colonies of the activated Saccharomyces cerevisiae GCC-2 in step 11) were picked and placed in YPD medium, and cultured at 30° C. and 180 rpm for 48 h to obtain a primary seed solution of Saccharomyces cerevisiae GCC-2.

[0071] 3) Secondary seed solution culture: The primary seed solution of Saccharomyces cerevisiae GCC-2 was transferred to fresh YPD medium at a 1% inoculum rate and cultured at 30°C and 180 rpm for 24 h to obtain the secondary seed solution of Saccharomyces cerevisiae GCC-2.

[0072] 3. Solid fermentation

[0073] 1) The cultured Saccharomyces cerevisiae GCC-1 secondary seed solution was inoculated into a solid fermentation medium at a rate of 5% by weight of the medium and mixed thoroughly. The solid fermentation product, GCC-1, was obtained by static incubation at 30°C for 96 h. The biomass of the solid fermentation product, GCC-1, was then counted by YPD plate counting. The results are shown in Table 1.

[0074] 2) The cultured Saccharomyces cerevisiae GCC-2 secondary seed solution was inoculated into the solid fermentation medium at a rate of 5% by weight of the culture medium and mixed thoroughly. The solid fermentation product, GCC-2, was obtained by static incubation at 30°C for 96 h. The biomass of the solid fermentation product, GCC-2, was then counted by YPD plate counting. The results are shown in Table 1.

[0075] 3) Equal volumes of the cultured secondary seed liquid of Saccharomyces cerevisiae GCC-1 and Saccharomyces cerevisiae GCC-2 were mixed. The mixed solution was inoculated into a solid fermentation medium at a concentration of 5% by weight of the culture medium and mixed thoroughly. The solid fermentation product, GCC-1 + GCC-2, was obtained by static incubation at 30°C for 96 hours. The biomass of the solid fermentation product, GCC-1 + GCC-2, was then counted by YPD plate counting. The results are shown in Table 1.

[0076] Table 1. Yeast solid fermentation biomass

[0077]

[0078] 4. High temperature drying:

[0079] The solid fermentation product GCC-1 was dried at 70° C. for 24 hours to obtain yeast culture GCC-1 (the yeast culture comprises fermentation medium, fermentation product, and bacteria).

[0080] The solid fermentation product GCC-2 was dried at 70° C. for 24 hours to obtain yeast culture GCC-2.

[0081] The solid fermentation product GCC-1+GCC-2 was dried at 70° C. for 24 h to obtain yeast culture GCC-1+GCC-2.

[0082] Example 2 Preparation of carp yeast culture-added feed

[0083] 1. Configuration of carp feed

[0084] The carp feed was prepared according to Table 2, with 1% compound premixed feed for aquatic animals (Beijing Xinlu United Aquatic Technology Co., Ltd.) used as the premix, and the other materials were common commercial materials.

[0085] The feed was divided into four treatment groups: a control group, a GCC-1 supplemented group, a GCC-2 supplemented group, and a GCC-1 + GCC-2 supplemented group. The fermentation culture addition method is shown in the table below: the control group was supplemented with 0.5% solid fermentation medium; the GCC-1 group was supplemented with GCC-1 yeast culture to a GCC-1 bacterial content of 2×10 10 cells / kg, and the mass was supplemented by solid fermentation medium; GCC-2 yeast culture was added to the GCC-2 group to make the GCC-2 bacterial content reach 2×10 10 cells / kg, and the mass was supplemented by solid fermentation medium; the GCC-1+GCC-2 group was supplemented with compound yeast culture to make the yeast content reach 2×10 10 cells / kg, and the rest of the mass was made up by solid fermentation medium. That is to say, per 1kg of feed, the Control group did not contain Saccharomyces cerevisiae GCC-1 and Saccharomyces cerevisiae GCC-2; the GCC-1 supplemented group contained 2×10 10 cells of Saccharomyces cerevisiae GCC-1; the GCC-2 supplemented group contained 2×10 10 cells of Saccharomyces cerevisiae GCC-2; the GCC-1+GCC-2 supplemented group contained a total of 2×10 10 cell.

[0086] Table 2. Yeast culture feed additives

[0087]

[0088]

[0089] 2. Feed ingredient testing

[0090] The moisture, ash, protein, and fat content of the four feeds in step 1 were tested according to the following methods, and the results are shown in Table 3. As can be seen from Table 3, there was no significant difference in the mass percentages of moisture, ash, crude protein, crude fat, crude protein dry weight, and crude fat dry weight among all groups.

[0091] The moisture content of the feed was determined by referring to the method described in "Determination of Moisture in Feeds" (GB / T 6435-2014). The crude ash content of the feed was determined by referring to the method described in "Determination of Crude Ash in Feeds" (GB / T 6438-2007). The crude protein content of the feed was determined by referring to the method described in "Determination of Crude Protein in Feeds" (GB / T 6432-1994). The crude fat content of the feed was determined by referring to the method described in "Determination of Crude Fat in Feeds" (GB / T 6433-2006).

[0092] Table 3 Basic ingredients of feed (%)

[0093]

[0094] Note: WT means wet weight, DM means dry weight.

[0095] Example 4: Breeding Method and Ecological Testing of Carp by Adding Yeast Culture to Feed

[0096] 1. Carp breeding methods

[0097] Carp were temporarily raised in a standard circulating water system for 2 weeks. After 24 hours of starvation, 192 healthy and uniform carp were randomly divided into 4 groups, with 4 replicates in each group and 12 carp in each replicate.

[0098] The water source was aerated and dechlorinated tap water, with continuous oxygenation for 24 hours during the culture process. A commercial fish recirculating water culture system was used for the culture system. Each cylinder measured 43 cm × 49 cm × 50 cm. The culture tank capacity was 90 L, with an inflow rate of 90 L / h. The culture water temperature was maintained at 26°C, with dissolved oxygen (DO) ≥ 6 mg / L, ammonia nitrogen content < 0.1 mg / L, and nitrite concentration < 0.05 mg / L.

[0099] The four feeds with the formula shown in Table 2 were used for feeding, 3 times a day, 2% of body weight for 7 days, 3% of body weight for 7 days, 6% of body weight for 11 days, 9% of body weight for 14 days, and 12% of body weight for 17 days.

[0100] 2. Ecological parameter detection

[0101] The initial body weight of fish in each group was measured, and after 8 weeks of feeding, the weight gain, feed conversion ratio (FCR) and survival rate were measured. Figure 1 shown.

[0102] Weight gain, feed conversion ratio (FCR), and survival rate were measured in each group. There were no significant differences (P>0.05) between the GCC-1, GCC-2, and GCC-1+GCC-2 groups and the control group. These results suggest that supplementing the feed with yeast culture has no significant effect on the growth performance and survival rate of common carp.

[0103] Example 5 Effect of Yeast Culture Added to Feed on Carp Liver

[0104] 1. Carp cultured to day 18 in Example 4 were collected (6 fish were taken from each parallel sample), and liver tissue, fresh blood, intestinal tissue and tail vein blood of each carp were collected for subsequent related tests.

[0105] 2. Liver triglyceride (TAG) detection

[0106] The liver samples collected in step 1 were homogenized with 1% PBS, and the TAG content in the samples was determined according to the TAG detection kit method. The free glucose reagent and triglyceride reagent TAG quantification kit were purchased from Sigma-Aldrich, Shanghai.

[0107] The results are as follows Figure 2 As shown in the data, compared with the control group, the liver TAG content in the GCC-1 and GCC-2 groups decreased to a certain extent, and the liver TAG content in the GCC-1+GCC-2 group was significantly lower than that in the control group, indicating that the addition of GCC-1+GCC-2 composite yeast culture to feed can reduce liver TAG content.

[0108] 3. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) testing

[0109] According to the method described in the serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity detection kit (Nanjing Jiancheng Bioengineering Institute), the fresh blood collected in step 1 was allowed to stand at 4°C for 10 minutes. After the transparent liquid was precipitated, it was centrifuged at 4000 rpm for 10 minutes. The supernatant (serum) was aspirated and the content level of phenylhydrazone, the product of the transaminase-catalyzed reaction, was assessed by the absorbance value at 520 nm using the colorimetric principle.

[0110] The results are as follows Figure 3 As shown, there was no significant difference between the GCC-1 group, the GCC-2 group, and the GCC-1+GCC-2 group and the control group, indicating that there was no liver damage.

[0111] 4. Expression of liver inflammatory factors

[0112] Total RNA was extracted from an appropriate number of liver tissue samples from each carp obtained in step 1 using the RTSuperMix cDNA synthesis kit (purchased from Tiangen Biochemical Technology (Beijing) Co., Ltd.). The expression levels of inflammation-related genes, such as TNF-α, IL-1β, TGF-β, and IL-10, in the cDNA were analyzed using quantitative PCR. Primer information is shown in Table 4.

[0113] Table 4 Primer sequence list

[0114]

[0115] The results are as follows Figure 4 As shown, there was no significant difference in the pro-inflammatory factor TNF-α between the groups. However, the GCC-2 group and the GCC-1+GCC-2 group significantly reduced the expression of the pro-inflammatory factor IL-1β. The GCC-1+GCC-2 group activated the expression of the anti-inflammatory factor TGF-β, with a significant increase in TGF-β. The GCC-2 group and the GCC-1+GCC-2 group both significantly increased the expression of the anti-inflammatory factor IL-10, with the GCC-1+GCC-2 group showing a higher level of expression. These results indicate that the compound yeast culture has anti-inflammatory properties and has an immune-protective effect on the liver.

[0116] Example 6 Effect of Yeast Culture Added to Feed on Carp Intestine

[0117] 1. Intestinal antioxidant capacity

[0118] The intestinal tissue collected in step 1 of Example 5 was used to measure the biochemical indicators T-AOC and SOD in the intestinal tissue using total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) detection kits according to the kit instructions. The total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) detection kits were purchased from Nanjing Jiancheng Bioengineering Research Institute Co., Ltd.

[0119] The results are as follows Figure 5 As shown, the addition of GCC-1, GCC-2, and compound yeast culture to feed increased the levels of antioxidant markers T-AOC and SOD in the intestine. The T-AOC and SOD levels in the compound yeast culture-added feed group were significantly higher than those in the control group, indicating an improvement in the body's intestinal antioxidant capacity.

[0120] 2. Intestinal damage index detection

[0121] Serum lipopolysaccharide (LPS) and diamine oxidase (DAO) activity assays were performed. Blood was collected from the tail vein, placed on ice for 10 minutes, and then centrifuged at 4000 rpm for 10 minutes. The supernatant was collected as serum and analyzed for biochemical parameters using a serum lipopolysaccharide (LPS) assay kit and a diamine oxidase (DAO) assay kit. Both the serum lipopolysaccharide (LPS) assay kit and the diamine oxidase (DAO) assay kit were purchased from Jiangsu Jingmei Biotechnology Co., Ltd.

[0122] The results are as follows Figure 6 Supplementation with GCC-1, GCC-2, and compound yeast cultures reduced serum LPS levels. Serum LPS levels in carp fed the compound yeast culture diet were significantly lower than in the control group. Serum DAO levels in carp fed the diets supplemented with GCC-2 and compound yeast cultures were also significantly lower than in the control group. These results suggest that the addition of compound yeast cultures has a protective effect on the intestinal mucosa and improves the intestinal barrier function of fish.

[0123] Example 7 Antiviral effect of yeast culture added to feed on carp

[0124] Dissolve SVCV virus seeds on ice and pipette 5 μL into 10 mL of MEM medium containing 10% fetal bovine serum; transfer the virus-containing MEM medium to a culture dish containing EPC cells and culture at 25°C and 5% CO2 until 80% of the cells show pathological effects; quickly freeze the culture dish in a -80°C refrigerator, then thaw it at room temperature, and repeat freezing and thawing three times to release the virus; centrifuge at 8000r at room temperature for 20 minutes, and collect the supernatant.

[0125] With about 10 6 Cultured carp (carp remaining from Example 4, cultured to day 18) were inoculated with TCID50 of SVCV for 7 days. Carp kidneys were randomly selected from 24 fish in each feeding group, and 4 fish were pooled into a replicate, with 6 replicates per group. qPCR analysis of SVCV viral expression was performed using primers shown in Table 4.

[0126] The results are as follows Figure 7 As shown in the figure, on the 7th day of infection, compared with the control group, the expression of SVCV in each treatment group decreased to a certain extent, and the expression level of the group supplemented with compound yeast culture feed was significantly lower than that of the control group, which inhibited the replication of SVCV in the fish and had a certain antiviral effect.

[0127] The present invention has been described in detail above. It will be apparent to those skilled in the art that the present invention may be practiced over a wide range of parameters, concentrations, and conditions without departing from the spirit and scope of the present invention and without unnecessary experimentation. Although specific embodiments have been given herein, it should be understood that further modifications may be made to the present invention. In summary, this application is intended to encompass any variations, uses, or improvements to the present invention, including those made by conventional techniques known in the art that depart from the scope of the present invention. Applications of the essential features may be made within the scope of the following claims.

Claims

1. A bacterial agent, characterized in that: The active ingredient of the bacterial agent is Saccharomyces cerevisiae ( Saccharomyces cerevisiae ); the cerevisiae yeast is a cerevisiae yeast strain numbered GCC-1 and a cerevisiae yeast strain numbered GCC-2, and the inoculation ratio of the cerevisiae yeast strain numbered GCC-1 and the cerevisiae yeast strain numbered GCC-2 in the bacterial agent is 1:1, wherein the cerevisiae yeast strain numbered GCC-1 has a registration number of CGMCC No. 21819 at the China Culture Collection Center for General Microorganisms; the cerevisiae yeast strain numbered GCC-2 has a registration number of CGMCC No. 21818 at the China Culture Collection Center for General Microorganisms.

2. Use of the bacterial agent according to claim 1 in preparing a carp feed additive or carp feed.

3. A carp feed additive, characterized in that: The carp feed additive contains the bacterial agent according to claim 1.

4. A carp feed, characterized in that: The carp feed contains the bacterial agent according to claim 1 or the carp feed additive according to claim 3.

5. The carp feed according to claim 4, characterized in that The amount of brewer's yeast added to the feed is 2×10 10 cells / kg.

6. Use of the bacterial agent according to claim 1 or the carp feed additive according to claim 3 in preparing carp feed for any of the following purposes: 1) Reduce TAG content and the expression of the pro-inflammatory factor IL-1β in carp liver, and activate the expression of the anti-inflammatory factors TGF-β and IL-10 in carp liver; 2) Increase the levels of antioxidant indicators T-AOC and SOD in the intestine of carp; 3) Reduce the activity of serum lipopolysaccharide and diamine oxidase in carp; 4) Inhibit SVCV replication in carp kidney.

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