Method for fermenting radix astragali through rhodococcus and application of method in aquaculture

Abstract

The invention provides a method for fermenting astragalus membranaceus through rhodococcus and application of the method in aquaculture. The method comprises the following steps that astragalus membranaceus is smashed, astragalus membranaceus fine powder is obtained, the astragalus membranaceus fine powder and amino acid raw powder are mixed, sterilized and then cooled, and mixed powder is obtained; adding sterile water into the mixed powder to prepare a fermentation culture medium; inoculating rhodococcus into the fermentation culture medium, uniformly mixing, fermenting for 22-26 hours under a constant-temperature condition and an aerobic condition, and then performing anaerobic fermentation for 70-76 hours to finish fermentation; and drying the fermented product, and pulverizing to obtain the product. According to the method, the obstruction of the cell wall structure of the astragalus membranaceus is effectively solved through a microbial fermentation technology, and synergistic substances such as small molecule peptides and organic acids are generated, so that the extraction of effective substances of the astragalus membranaceus is increased, and the bioavailability of Chinese herbal medicines is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of microbial technology, specifically to a method for fermenting Astragalus membranaceus with Rhodococcus and its application in aquaculture. Background Technology

[0002] Astragalus, a perennial herb, is sweet in taste and slightly warm in nature. It possesses the effects of tonifying qi and strengthening the exterior, as well as promoting diuresis and reducing swelling. Studies have shown that astragalus contains various components such as saponins, flavonoids, polysaccharides, and amino acids, among which astragalus polysaccharides are one of its main active ingredients. Numerous studies have demonstrated that astragalus polysaccharides exhibit a variety of biological activities, including promoting immune regulation, anti-tumor activity, antiviral activity, anti-radiation activity, anti-aging activity, and antiparasitic activity. Furthermore, due to its advantages of low toxicity, no residue, and no drug resistance, it has been widely used in immune enhancers and antiviral drugs.

[0003] Traditional Chinese medicine (TCM) herbs have been used as feed additives in China for a long time. The famous agricultural classic *Qimin Yaoshu* records their multifaceted effects in livestock and aquaculture, possessing both nutritional and medicinal properties. However, unprocessed Astragalus membranaceus (Huangqi) suffers from problems such as dense cell wall structure and low dissolution rate of active ingredients, necessitating effective extraction techniques for its active components. Currently, there are few reports on the use of specific microorganisms for fermentation of TCM herbs.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The primary objective of this invention is to provide a method for fermenting Astragalus membranaceus using Rhodococcus bacteria. This method effectively overcomes the obstacles posed by the cell wall structure of Astragalus membranaceus through microbial fermentation technology, while simultaneously generating synergistic substances such as small molecule peptides and organic acids, thereby increasing the extraction of effective substances from Astragalus membranaceus and significantly improving the bioavailability of traditional Chinese medicine.

[0006] The second objective of this invention is to provide Rhodococcus fermented Astragalus powder obtained by the above-mentioned method of fermenting Astragalus with Rhodococcus. This fermented Astragalus has good effects on improving the gastrointestinal health of aquatic animals, promoting the growth of aquatic animals, regulating the immune system of aquatic animals, and enhancing the antioxidant, stress-resistant and disease-resistant capabilities of aquatic animals. At the same time, compared with traditional preparations, the fermented preparation obtained by this invention has the advantages of low toxicity, low residue and high efficiency.

[0007] The third objective of this invention is to provide the application of Rhodococcus pyogenes fermented Astragalus membranaceus powder in aquaculture. By feeding Rhodococcus pyogenes fermented Astragalus membranaceus to fish, the effects of its effects on fish growth performance, digestive enzyme activity (pepsin, intestinal amylase), antioxidant indicators (SOD, MDA, GSH-Px, etc.), and non-specific immune parameters (ACP, AKP, etc.) will be systematically evaluated. Furthermore, its disease-resistant potential will be verified through Vibrio harveyi challenge experiments. The research results will reveal the target mechanisms by which feeding Rhodococcus pyogenes fermented Astragalus membranaceus regulates the health of grouper, aiming to provide theoretical support for developing precise nutritional intervention strategies based on fermentation in grass carp.

[0008] To achieve the above-mentioned objectives of this invention, the following technical solution is adopted:

[0009] This invention provides a method for fermenting Astragalus membranaceus with Rhodococcus, comprising the following steps:

[0010] S1. Pulverize Astragalus membranaceus to obtain Astragalus membranaceus fine powder, mix the Astragalus membranaceus fine powder with amino acid raw powder, sterilize and cool to obtain mixed powder;

[0011] S2. Add sterile water to the mixed powder to prepare a fermentation culture medium;

[0012] S3. Inoculate the fermentation medium with Rhodococcus, mix well, and ferment under constant temperature and aerobic conditions for 22-26 hours, followed by anaerobic fermentation for 70-76 hours to complete the fermentation.

[0013] S4. After the fermentation is complete, dry the product and grind it into powder to obtain the final product.

[0014] Preferably, fermentation is carried out for 24 hours under aerobic conditions and 72 hours under anaerobic conditions;

[0015] Preferably, the Astragalus membranaceus powder is passed through a 100-mesh sieve;

[0016] Preferably, the sterilization method is to sterilize at 121°C for 15-20 minutes, preferably for 20 minutes;

[0017] Preferably, in the powder preparation step, the powder is passed through a 50-mesh sieve.

[0018] Preferably, as a further specific embodiment, the mass ratio between the Astragalus membranaceus fine powder and the amino acid raw powder in step S1 is 1:(0.04-0.08);

[0019] Preferably, the mass ratio between the astragalus powder and the amino acid powder is 1:0.05.

[0020] Preferably, as a further specific embodiment, in step S3, the ratio of the mass of the fermentation medium to the mass of the inoculated Rhodococcus is 1:(0.005-0.02);

[0021] Preferably, the ratio of the mass of the fermentation medium to the mass of the inoculated Rhodococcus is 1:0.02.

[0022] Preferably, as a further specific embodiment, the water content of the fermentation medium prepared in step S2 is 48%-52%;

[0023] Preferably, the fermentation medium has a water content of 50%.

[0024] Preferably, as a further specific embodiment, the constant temperature in S3 is 32℃-37℃;

[0025] Preferably, the constant temperature is 35°C.

[0026] Preferably, as a further specific embodiment, the erythrococcus is pyridine-loving erythrococcus.

[0027] Rhodococcus pyridostigmine is a type of Gram-positive bacterium with broad-spectrum substrate degradation capabilities. The enzymes it contains can enhance the antiviral ability of aquatic animals and provide good resistance to various metal ions in a variety of water bodies and aquatic feeds. Therefore, Astragalus membranaceus fermented with Rhodococcus pyridostigmine exhibits good stress resistance. At the same time, fermented Astragalus membranaceus has good effects on improving the gastrointestinal health of aquatic animals, promoting their growth, regulating their immune system, and enhancing their antioxidant, stress-resistant, and disease-resistant abilities.

[0028] The present invention also provides Rhodococcus fermented astragalus powder prepared by the above-described method of fermenting astragalus with Rhodococcus.

[0029] This invention also provides the application of the above-mentioned Rhodococcus fermented Astragalus membranaceus in aquaculture;

[0030] Preferably, the aquatic product is fish;

[0031] Preferably, the aquatic product is the pearl grouper.

[0032] The present invention also provides an additive for aquaculture feed, comprising the above-mentioned cocci-fermented astragalus powder.

[0033] This invention also provides an application of Rhodococcus fermented Astragalus powder in the preparation of aquaculture feed.

[0034] Preferably, as a further specific embodiment, the amount of Rhodococcus fermented Astragalus powder added to the feed is 0.5%-2% of the feed mass;

[0035] Preferably, the amount of Rhodococcus fermented Astragalus powder added to the feed is 1% of the feed mass.

[0036] Preferably, the prepared Rhodococcus fermented Astragalus powder is added to the finished feed, wherein the nutritional components of the finished feed include: crude protein ≥48.0%, crude fat ≥10.0%, crude fiber ≤3.0%, crude ash ≤16.0%, lysine ≥2.5%, moisture ≤10.0%, total phosphorus 1.5%-3.0%, and 1% sodium alginate.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] This method effectively overcomes the obstacles posed by the cell wall structure of Astragalus membranaceus through microbial fermentation technology, while simultaneously generating synergistic substances such as small molecule peptides and organic acids, thereby increasing the extraction of effective substances from Astragalus membranaceus and significantly improving the bioavailability of traditional Chinese medicine. Furthermore, this fermented Astragalus membranaceus exhibits good effects in improving the gastrointestinal health of aquatic animals, promoting their growth, regulating their immune system, and enhancing their antioxidant, stress-resistant, and disease-resistant capabilities. Compared with traditional preparations, the fermented preparation obtained by this invention combines the advantages of low toxicity, low residue, and high efficiency. Detailed Implementation

[0039] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0040] Example

[0041] This experiment was supported by Boran Biotechnology Co., Ltd., which provided the site and aquaculture facilities. The pearl grouper used in the experiment was provided by Tianjin Hengqian Aquatic Products. Fish of good health and uniform size were selected as experimental subjects. After being acclimatized to commercial feed for one week at the experimental aquaculture site, they were used for the aquaculture experiment.

[0042] Amino acid powder (purchased from Tianjin Boran Biotechnology Co., Ltd., trade name: Compound Amino Acid Powder) and Rhodococcus erythropolis solution were prepared by the laboratory of Tianjin Agricultural College. All other inorganic salts and reagents were domestically produced analytical grade. Astragalus membranaceus was purchased from Gansu Changzheng Group's Huining Astragalus membranaceus slices.

[0043] A. Preparation of Astragalus powder fermented with Rhodococcus pneumoniae

[0044] All raw materials were dried in an oven at 55°C for 24 hours before use.

[0045] Astragalus membranaceus slices purchased from Gansu Changzheng Group were pulverized and passed through a 100-mesh sieve to obtain fine astragalus powder. The fine astragalus powder was weighed, along with 5% of its mass as amino acid raw powder. The two were mixed and then sterilized in a high-temperature, high-pressure steam sterilizer at 121°C for 20 minutes, followed by cooling to room temperature. Sterile water was added to the mixed powder until the moisture content reached 50%, thus preparing a fermentation medium. 2% of the fermentation medium, along with 2% of its mass as Rhodococcus pyridostigmine, was weighed and mixed. The mixture was then placed in a constant temperature incubator at 35°C, sealed with three layers of gauze, and subjected to aerobic fermentation for 24 hours. Subsequently, the mixture was tightly sealed with plastic wrap and rubber bands and subjected to anaerobic fermentation for 72 hours. After fermentation, the material was dried for 24 hours, then pulverized and passed through a 50-mesh sieve, finally producing fermented astragalus.

[0046] B. Preparation of experimental feed

[0047] The Haitong Haoshi No. 4 EP grouper commercial feed produced by Santong Bioengineering (Weifang) Co., Ltd. was used as the base material. Its nutritional composition is as follows: crude protein ≥48.0%, crude fat ≥10.0%, crude fiber ≤3.0%, crude ash ≤16.0%, lysine ≥2.5%, moisture ≤10.0%, and total phosphorus 1.5%-3.0%. The raw feed was crushed and passed through a 50-mesh sieve. 1% sodium alginate was added as a binder. Group T1 was supplemented with 1% pure astragalus powder, and Group T2 was supplemented with 1% Rhodococcus pyridostigmine fermented astragalus powder. Both groups were mixed with water, combined, and re-granulated according to the original particle size. The pellets were then dried at 55℃ to constant weight. Group T3 was sprayed with 1% Rhodococcus pyridostigmine bacterial solution after pelleting. The control group used the base feed directly as a control. All feeds were stored at room temperature, protected from light and moisture.

[0048] C. Experimental Design and Feeding Management

[0049] After the experimental fish were temporarily kept without food for 24 hours, a total of 240 pearl grouper with an initial body weight of (9.56±1.14)g were selected and randomly divided into a control group and four experimental groups (T1, T2, and T3). Each group had two replicates, with 30 fish in each replicate.

[0050] The experiment was conducted at a fish farm in Tianjin, using 250L open tempered glass tanks as the rearing units. A 28-day conventional rearing period and a 10-day challenge period were established. The water was maintained at a salinity of 25‰ and a constant temperature of 24±0.5℃. Dynamic water quality control indicators were: ammonia nitrogen <0.1mg / L, nitrite <0.05mg / L, and pH 7.8–8.4. Feeding was conducted daily at 08:00 and 16:00 using the satiating method (until feeding ceased), and the amount fed was recorded. The behavior and body condition of the pearl grouper were observed simultaneously. After morning feeding, uneaten food and excrement were siphoned from the bottom of the tank, and 30%–40% of the water was changed, with isothermal saline added to maintain the stability of the biological filtration system.

[0051] After 28 days, following initial sampling and observation, 10 fish were retained in each culture tank for a challenge experiment. The challenge experiment used Vibrio harveyi, provided by Tianjin Agricultural College, at a concentration of 1×10⁻⁶. 8 The fish were injected intraperitoneally with CFU / g. The volume of the injected bacterial solution was 1% of the fish's body weight per fish, depending on the fish's weight. The fish were fed daily according to the farming method. The condition of the fish was observed and recorded for 10 days.

[0052] Experimental Example 1: Determination of growth performance, digestive enzymes, antioxidant and non-specific immune indicators

[0053] Measurement and calculation of growth performance indicators

[0054] Sampling was conducted on days 0, 14, and 28 of the experiment: the pearl grouper was rinsed with physiological saline containing 1% heparin sodium, and body weight and length were measured for each fish. Growth performance and feed utilization indicators were calculated based on the following formula:

[0055] 1. Body weight growth rate (WGR):

[0056] R WGR =(W t -W0) / W0×100%2. Specific Growth Rate (SGR):

[0057] R SGR =(ln W) t -ln W0) / t×100%3. Survival rate (SR):

[0058] R S =N t / N0×100%4. Feed conversion ratio (FCR):

[0059] R FCR =F / (W) t -W0)5. Visceral-to-body ratio (VSI):

[0060] RVSI =W v / W×100%.

[0061] W t W0 represents the final weight of the grouper (g); W0 represents the initial weight of the grouper (g); t represents the rearing time, N t N represents the number of surviving animals at the end; N0 represents the number of animals released at the beginning; F represents the amount of bait consumed (g); W v W represents the weight of the internal organs (g); W represents the weight of the fish body (g).

[0062] Sampling was conducted on days 0, 14, and 28 of the experiment: Five fish were randomly selected from each treatment group, and blood was drawn from their tail veins using a sterile medical syringe rinsed with 1% heparin sodium saline. The blood samples were placed in blood collection tubes and stored at 4°C for 4 hours, followed by centrifugation at 5000 rpm for 10 minutes to prepare serum. The serum was then separated and stored at -20°C for later use. Tissues and organs were excised, aliquoted, labeled, and stored at -80°C for later testing. This assay is used to detect peroxidase (POD), total antioxidant (T-AOC), superoxide dismutase (SOD), malondialdehyde (MDA), catalase (CAT), glutathione (GSH), acid phosphatase (ACP), alkaline phosphatase (AKP), aspartate aminotransferase (GOT), alanine aminotransferase (GPT), lysozyme (LZM), acetylcholinesterase (AChE), lipase, pepsin, trypsin, and α-amylase. After a 10-day challenge period, blood and tissue samples were collected using the above procedures to determine antioxidant and non-specific immune indicators.

[0063] The experimental data were preprocessed and organized using Excel 2007 software, and one-way ANOVA was performed using IBM SPSS Statisics 23 software. If significant differences were found, Duncan's method was used for multiple comparisons. P < 0.05 indicated significant differences. Data are expressed as mean ± standard deviation.

[0064] The experimental results are shown in Table 1. The effects of *Rhodococcus faecalis*-fermented astragalus on the growth performance of pearl grouper showed significant differences. Group T2 (basal feed supplemented with fermented astragalus) performed best, with a survival rate of 100%, the highest specific growth rate and growth rate among all groups, and a significantly lower feed conversion ratio than other groups (p<0.05). Group T1 (supplemented with pure astragalus) had a survival rate of 90%, and its specific growth rate and feed conversion ratio were lower than those of group T2. Group T3 showed no significant difference in specific growth rate compared to the control group, but its feed conversion ratio was significantly higher. The viscera-to-body ratio showed little difference among the groups and did not significantly alter visceral development.

[0065] Table 1 Effects of Rhodococcus fermentation of Astragalus membranaceus on growth performance of pearl grouper

[0066]

[0067] Experiment Example 2: Effects of Rhodococcus fermented Astragalus on non-specific immune markers in pearl grouper

[0068] The experimental results are shown in Table 2. The liver ACP and AKP activities in group T2 were significantly higher than in other groups (P<0.05), while the blood GOT and GPT levels were the lowest. In contrast, the GOT and GPT values ​​in groups T3 and CK were significantly increased. Regarding muscle immune function, the LMZ activity in group T2 was significantly better than in other groups (P<0.05). In terms of liver metabolism, the challenge treatment significantly affected the activities of acid phosphatase (ACP) and alkaline phosphatase (AKP). Group T2 showed the highest ACP activity, significantly higher than the control group; AKP activity was also significantly higher than the control group (P<0.05). Blood transaminase analysis showed that GOT and GPT in group T2 were significantly lower than in other groups. In muscle tissue, the lysozyme (LMZ) activity in group T2 was 47.5% higher than in the control group, while there was no significant difference in acetylcholinesterase (AChE).

[0069] Table 2. Effects of Rhodococcus fermented Astragalus membranaceus on non-specific immune indicators in pearl grouper.

[0070]

[0071] Experiment Example 3: Effects of Rhodococcus fermentation of Astragalus membranaceus on the digestive enzyme activity of pearl grouper

[0072] The experimental results are shown in Table 3. Rhodococcus fermentation of Astragalus membranaceus significantly enhanced the digestive enzyme activity of pearl grouper, with group T2 showing the best performance among all indicators. Lipase activity in group T2 was significantly higher than other groups (P<0.05); pepsin and trypsin activities were also significantly higher than the control group (P<0.05). Furthermore, α-amylase activity in group T2 was significantly better than other treatment groups (P<0.05). Groups T1 and T3 showed significantly higher lipase, pepsin, and trypsin activities than the control group (P<0.05).

[0073] Table 3: Effects of Rhodococcus fermentation of Astragalus membranaceus on the digestive enzyme activity of pearl grouper

[0074]

[0075] Experiment Example 4: Effects of Rhodococcus fermentation of Astragalus membranaceus on the antioxidant capacity of pearl grouper

[0076] The experimental results are shown in Table 4. The liver peroxidase (POD) activity and total antioxidant capacity of group T2 were significantly higher than other groups (P<0.05), and the activities of catalase and glutathione were also significantly better than other treatment groups (P<0.05). Among the muscle oxidative stress indicators, group T2 had the lowest malondialdehyde (MDA) content, significantly lower than the control group and group T3. Superoxide dismutase (SOD) activity was highest in group T1 and significantly higher in group T2 than in the control group (P<0.05). Group T3 showed the worst performance in liver antioxidant enzymes (such as CAT and GSH) and muscle MDA. In the challenge test, the peroxidase (POD), total antioxidant capacity (T-AOC), catalase (CAT), and glutathione (GSH) activities of group T2 were significantly higher than those of the control group. Muscle oxidative stress indicators showed that the control group had the highest MDA content, while group T2 showed a significant decrease (P<0.05); simultaneously, the challenge treatment significantly increased superoxide dismutase (SOD) activity. T2 treatment had the most significant effects on improving liver antioxidant capacity and reducing muscle MDA.

[0077] Table 4: Effects of Rhodococcus fermentation of Astragalus membranaceus on antioxidant capacity of pearl grouper

[0078]

[0079] Experiment Example 5: Effects of Rhodococcus fermented Astragalus on disease resistance in pearl grouper

[0080] The experimental results are shown in Table 5. After the experimental fish were fed using different methods and challenged with Vibrio harveyi, the experimental group showed significantly improved resistance to Vibrio harveyi and reduced mortality compared with the control group. Among them, the group fed with fermented Astragalus membranaceus of Rhodococcus had a survival rate of 100% and the lowest mortality rate.

[0081] Table 5: Relative mortality and relative survival rates after challenge with Vibrio harveyi

[0082]

[0083]

[0084] The experimental data above show that enzymes produced during microbial fermentation can effectively decompose plant cell walls, allowing active ingredients to be released from the cells, thereby improving the medicinal effects of traditional Chinese herbal medicines.

[0085] The dense cell walls of Astragalus membranaceus can be broken down by enzymes during fermentation by Rhodococcus pyridostigmine, releasing various nutrients from the cells and thus enhancing the medicinal effects of this traditional Chinese herbal medicine. This experiment took place during the summer in Tianjin. For several days, the growth of pearl grouper was reduced due to the hot weather. However, adding fermented Astragalus membranaceus to the feed improved the various growth performances of the pearl grouper and reduced the feed conversion ratio. Through fermentation by Rhodococcus pyridostigmine, the polysaccharides in Astragalus membranaceus were successfully released to the extracellular space, resulting in a significant increase in their conversion rate. The T2 group showed excellent performance across all indicators, fully demonstrating that Rhodococcus pyridostigmine effectively promotes the digestion and absorption of nutrients in fish during the fermentation of Astragalus membranaceus, thus having a positive effect on fish growth.

[0086] The experimental results of this invention show that adding fermented Astragalus to the feed of pearl grouper resulted in a higher survival rate than adding unfermented Astragalus to the feed. This finding indicates that fermentation treatment reduces the potential toxic side effects of Astragalus as a traditional Chinese medicine on fish. This may be because Rhodococcus pyridostigmine decomposes and transforms the anti-nutritional components in Astragalus, improving the pharmacological properties of the herb and thus reducing its adverse effects on fish.

[0087] The results of this study indicate that adding an appropriate amount of Astragalus membranaceus fermented with Rhodococcus pyridococcus can significantly improve the survival rate, body weight gain rate, and specific growth rate of pearl grouper. It also significantly enhances the antioxidant capacity and non-specific immunity of pearl grouper. Furthermore, this additive helps to enhance the activity of lipase, α-amylase, pepsin, and trypsin in pearl grouper. It is recommended to add fermented Astragalus membranaceus to the diet of pearl grouper. The results of this study can accumulate basic data for the application of herbal additives in pearl grouper, and the additives are universally applicable to various fish species, making them suitable for widespread use in fish farming and providing a reference for the health of aquaculture fish.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fermenting Astragalus membranaceus with Rhodococcus, characterized in that, Includes the following steps: S1. Pulverize Astragalus membranaceus to obtain Astragalus membranaceus fine powder, mix the Astragalus membranaceus fine powder with amino acid raw powder, sterilize and cool to obtain mixed powder; S2. Add sterile water to the mixed powder to prepare a fermentation culture medium; S3. Inoculate the fermentation medium with Rhodococcus, mix well, and ferment under constant temperature and aerobic conditions for 22-26 hours, followed by anaerobic fermentation for 70-76 hours to complete the fermentation. S4. After the fermentation is complete, dry the product and grind it into powder to obtain the final product.

2. The method for fermenting Astragalus membranaceus with Rhodococcus according to claim 1, characterized in that, In step S1, the mass ratio between the Astragalus membranaceus powder and the amino acid powder is 1:(0.04-0.08). Preferably, the mass ratio between the astragalus powder and the amino acid powder is 1:0.

05.

3. The method for fermenting Astragalus membranaceus with Rhodococcus according to claim 1, characterized in that, In step S3, the ratio of the mass of the fermentation medium to the mass of the inoculated Rhodococcus is 1:(0.005-0.02). Preferably, the ratio of the mass of the fermentation medium to the mass of the inoculated Rhodococcus is 1:0.

02.

4. The method for fermenting Astragalus membranaceus with Rhodococcus according to claim 1, characterized in that, The fermentation medium prepared in step S2 has a water content of 48%-52%; Preferably, the fermentation medium has a water content of 50%; Preferably, the constant temperature in step S3 is 32℃-37℃; Preferably, the constant temperature is 35°C.

5. The method for fermenting Astragalus membranaceus with Rhodococcus according to claim 1, characterized in that, The erythrococcus mentioned is Rhodococcus pyridinophilus.

6. A Rhodococcus fermented Astragalus powder, characterized in that, It was prepared using the preparation method described in any one of claims 1-5.

7. The application of Rhodococcus fermented Astragalus powder as described in claim 6 in aquaculture; Preferably, the aquatic product is fish; Preferably, the aquatic product is the pearl grouper.

8. An additive for aquaculture feed, characterized in that, Includes the Rhodococcus fermented Astragalus powder as described in claim 6.

9. The application of Rhodococcus fermented Astragalus powder as described in claim 6 in the preparation of aquaculture feed.

10. The application of Rhodococcus fermented Astragalus powder according to claim 9 in the preparation of aquaculture feed, characterized in that, The amount of Rhodococcus fermented Astragalus powder added to the feed is 0.5%-2% of the feed mass; Preferably, the amount of Rhodococcus fermented Astragalus powder added to the feed is 1% of the feed mass.

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