Brown algae polysaccharide preparation, preparation method thereof and feed for resisting micropterus salmoides enteritis

Abstract

The invention provides a brown algae polysaccharide preparation, a preparation method thereof and a feed for resisting micropterus salmoides enteritis, the brown algae polysaccharide preparation is prepared based on precise regulation and dynamic staged extraction of complex enzyme, and specific brown algae polysaccharide is used as an active ingredient; experimental verification shows that by adding the fucoidan polysaccharide preparation into the micropterus salmoides feed, the intestinal function of the micropterus salmoides can be effectively enhanced, the inflammatory response is relieved, and the resistance of the micropterus salmoides to enteritis is improved; in the micropterus salmoides breeding process, the algal polysaccharide preparation is used as a feed additive, the morbidity of enteritis of the micropterus salmoides can be effectively reduced, the growth performance and breeding benefits of the micropterus salmoides can be improved, the algal polysaccharide preparation has the advantages of being natural, safe, free of residues and the like, an innovative and environment-friendly solution is provided for healthy breeding of the micropterus salmoides, and the algal polysaccharide preparation is worthy of popularization and application. Wide application prospects and important economic values are realized.

Description

Technical Field

[0001] The invention relates to the technical field of aquaculture, in particular to a brown algae polysaccharide preparation and a preparation method thereof, and a feed for resisting enteritis of California sea bass. Background Art

[0002] As an important freshwater farmed fish, California bass (Micropterus salmonides) occupies a prominent position in my country's aquaculture industry. Its delicious meat is deeply loved by consumers, and the market demand continues to grow. However, with the continuous expansion of farming scale and increasing farming density, California bass farming faces many challenges, among which the frequent outbreak of enteritis has become one of the key factors restricting the healthy development of its industry.

[0003] Enteritis has a high incidence rate during the breeding process of California bass, which is mainly caused by a variety of bacteria, viruses, and environmental stress factors. Sick California bass usually show symptoms such as loss of appetite, slow growth, intestinal congestion and inflammation, and in severe cases can lead to mass deaths. Traditional prevention and control methods mostly rely on antibiotics. Long-term use of antibiotics is not only prone to bacterial resistance and reduced drug efficacy, but also drug residues will have an adverse effect on the quality of California bass and endanger the health of consumers. It will also pollute the breeding water environment and destroy the ecological balance of the water.

[0004] As a kind of natural biomacromolecule extracted from seaweed, polysaccharides have multiple biological activities, such as immunomodulation, anti-oxidation, antibacterial and anti-inflammatory functions. Brown algae polysaccharides are rich in sulfate groups and have unique physiological activities. They are expected to effectively prevent and treat California bass enteritis by regulating the balance of intestinal microecology, enhancing intestinal mucosal immune function, and inhibiting the growth of pathogens. At the same time, they avoid the many disadvantages of antibiotics and provide a green, safe and efficient new solution for the healthy breeding of California bass, which meets the needs of sustainable development of modern aquaculture. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a brown algae polysaccharide preparation and a preparation method thereof, and a feed for resisting enteritis of California sea bass prepared using the brown algae polysaccharide preparation, so as to solve the problem of frequent enteritis in the breeding process of California sea bass and provide strong support for its healthy breeding. The technical scheme adopted by the present invention is as follows:

[0006] First, the present invention provides a method for preparing a brown algae polysaccharide preparation, comprising the following steps:

[0007] S1. freeze-dry the clean brown algae at -50°C to -60°C for 24-48 hours until the brown algae is dehydrated and becomes brittle, then crush the dehydrated brown algae into powder and pass through an 80-100 mesh sieve;

[0008] S2. Compounding cellulase, alginate and xylanase to obtain a composite enzyme preparation;

[0009] S3. The brown algae powder prepared in S1 was mixed with deionized water in a mass / volume ratio of 1:20-1:30 to form a uniform suspension, the pH was adjusted to 5.0-5.5, and then the complex enzyme preparation was added, the amount of the enzyme added was 1.0%-1.5% of the mass of the brown algae powder;

[0010] S4. After S3 configuration is completed, continuous enzymatic hydrolysis is performed. The enzymatic hydrolysis process takes a total of 4-6 hours and is divided into three stages:

[0011] The first stage lasts for 0-2 hours, with a pH of 5.0-5.5 and a temperature of 45-50°C. At the end of the first stage, solid-liquid separation is performed and the supernatant is collected;

[0012] The second stage lasts 0-2 hours after the first stage, the pH is adjusted to 5.5-6.0, the temperature is raised to 50-55°C, and at the end of the second stage, solid-liquid separation is performed and the supernatant is collected;

[0013] The third stage lasts for 0-2 hours after the second stage, the pH is adjusted to 6.0-6.5, the temperature is lowered to 45°C, and at the end of the third stage, solid-liquid separation is performed and the supernatant is collected;

[0014] S5. The supernatants collected in the three stages of S4 are combined, and impurities are removed using an ultrafiltration membrane with a relative molecular weight cutoff of 100 kDa. Then, the permeate is passed through an ultrafiltration membrane with a relative molecular weight cutoff of 10 kDa to further concentrate the polysaccharide solution;

[0015] S6. Desalting and purifying the concentrated polysaccharide solution prepared in S5 to obtain a brown algae polysaccharide preparation.

[0016] Preferably, in the above step S6, ion exchange chromatography is adopted, using a strongly acidic cation exchange resin and a strongly basic anion exchange resin to remove cations and anions in the solution in turn; the desalted polysaccharide solution is then purified by a gel permeation chromatography column, and the polysaccharide molecules are separated according to their size and shape differences, and the polysaccharide solution corresponding to a single elution peak is collected.

[0017] Preferably, in the above step S2, cellulase, alginate and xylanase are compounded in a mass ratio of 3:2:1.

[0018] The above method for extracting and preparing laminarin preparation has the following advantages:

[0019] 1. High extraction rate and purity: Through precise selection of compound enzyme system and control of enzymatic conditions, as well as dynamic segmented extraction strategy, the polysaccharide components in kelp can be fully released, and the extraction rate of polysaccharides can be significantly improved by 20%-30% compared with traditional methods. At the same time, through multi-step separation and purification technology, impurities can be effectively removed to obtain high-purity kelp polysaccharides with a purity of more than 95%.

[0020] 2. Unique structure and function: Dynamic segmented extraction and structural modification technology make the prepared kelp polysaccharide have unique structural characteristics, such as specific molecular weight distribution, degree of sulfation and substitution position, etc. These structural characteristics give the polysaccharide unique biological activity, such as stronger antioxidant capacity, immunomodulatory activity and anti-tumor activity, etc., and have broader application prospects in the fields of medicine, food, cosmetics, etc.

[0021] 3. Environmental protection and sustainability: This method uses mild enzymatic conditions, avoiding the use of a large amount of strong acid, strong alkali and organic solvents in traditional chemical extraction methods, reducing environmental pollution and energy consumption. At the same time, kelp, as a rich renewable resource, provides a sustainable source of raw materials for large-scale preparation of kelp polysaccharides.

[0022] In a second aspect, the present invention provides a fucoidan preparation, which is prepared by the above-mentioned method for preparing the fucoidan preparation.

[0023] In a third aspect, the present invention provides a feed for resisting enteritis of California sea bass, comprising the brown algae polysaccharide preparation as described above. Conventional California sea bass feed generally comprises fish meal, soybean meal, fish oil, wheat flour, vitamin premix, mineral premix and other ingredients, and the brown algae polysaccharide preparation can be directly mixed with the feed according to the mass ratio.

[0024] Preferably, the amount of the fucoidan preparation added to the feed is 0.1-0.3% of the total mass of the feed.

[0025] Most preferably, the amount of the fucoidan preparation added to the feed is 0.2% of the total mass of the feed.

[0026] The beneficial effects of the present invention are as follows: the brown algae polysaccharide preparation provided by the present invention can be used to prepare a feed additive for preventing and / or treating enteritis in California bass. The brown algae polysaccharide preparation is added to the feed and can enter the intestines during the feeding process of California bass to play a role, effectively preventing the occurrence of enteritis by regulating the intestines and enhancing intestinal function; and when California bass has already suffered from enteritis, it can promote the repair of intestinal tissues, reduce inflammatory reactions, and increase the recovery speed of California bass.

[0027] It has been verified by experiments that, during the breeding process of California bass, the brown algae polysaccharide preparation provided by the present invention is added to the feed of California bass. In breeding practice, the California bass is fed with an addition amount of 0.1%-0.3%. After a period of time, the incidence of California bass enteritis can be significantly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying creative labor, other drawings obtained based on these drawings still belong to the scope of the present invention.

[0029] Figure 1 To study the effects of adding different concentrations of brown algae polysaccharides to feed on the intestinal tissue morphology and related indicators of California bass;

[0030] Figure 2 Effects of adding different concentrations of brown algae polysaccharides to feed on intestinal immunity and antioxidant indicators of California bass

[0031] Figure 3 To investigate the effects of adding brown algae polysaccharides to feed on molecular indicators of intestinal immunity in a California sea bass enteritis model. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with embodiments and drawings.

[0033] First, a method for preparing kelp polysaccharides based on precise regulation of compound enzymes and dynamic segmented extraction is provided. This method innovatively combines a specific compound enzyme system with precise enzymatic hydrolysis condition control, and adopts a dynamic segmented extraction strategy to achieve efficient, high-purity preparation of kelp polysaccharides with specific structural and functional characteristics. Compared with traditional methods, this method can significantly improve the extraction rate and quality of kelp polysaccharides, while giving the polysaccharides unique biological activity.

[0034] Example 1 Extraction and Preparation of Laminarin Polysaccharide Preparation

[0035] Use the following steps:

[0036] 1. Raw material pretreatment

[0037] Select fresh, uncontaminated kelp, rinse it with deionized water to remove surface impurities, salt and microorganisms. Cut the washed kelp into small pieces, put it into a freeze dryer, and freeze dry it at -50℃ to -60℃ for 24-48 hours until the kelp is completely dehydrated and brittle. Then, use a grinder to crush the dried kelp into uniform powder and pass it through an 80-100 mesh sieve to ensure the uniformity of the subsequent enzymatic hydrolysis process.

[0038] 2. Screening and compounding of complex enzymes

[0039] Based on the in-depth analysis of the cell wall and polysaccharide structure of kelp, suitable enzymes were screened out. This method uses cellulase, alginate and xylanase in a specific ratio (3:2:1). Among them, cellulase can degrade the cellulose component in the cell wall of kelp, alginate can specifically decompose alginate, and xylanase helps to destroy the xylan structure in the cell wall. The three work synergistically to open the kelp cell structure to the greatest extent and release polysaccharides.

[0040] 3. Precise enzymatic hydrolysis condition control

[0041] The kelp powder and deionized water are mixed in a ratio of 1:20-1:30 (w / v) to form a uniform suspension. The suspension is transferred to a reactor equipped with a stirring device and a temperature control system, the pH is adjusted to 5.0-5.5, and then a composite enzyme preparation is added, and the amount of enzyme added is 1.0%-1.5% of the mass of the kelp powder.

[0042] During the enzymatic hydrolysis process, the temperature is strictly controlled at 45-50°C, and the stirring is continued at a speed of 100-150r / min to ensure that the enzyme is fully in contact with the substrate. At the same time, the online pH monitoring system is used to monitor the pH changes of the reaction system in real time, and the pH is stably controlled within the set range by adding dilute hydrochloric acid or sodium hydroxide solution. The enzymatic hydrolysis time is set to 4-6 hours, during which a small amount of reaction liquid is taken every 1 hour, and the release of polysaccharides is analyzed by high-performance liquid chromatography (HPLC) to determine the optimal enzymatic hydrolysis endpoint.

[0043] 4. Dynamic segmentation extraction

[0044] According to the release law and structural changes of polysaccharides during the enzymatic hydrolysis process, the enzymatic hydrolysis process is divided into three stages. In the first stage (0-2 hours), the cell wall is initially destroyed and some water-soluble polysaccharides are released. At this time, the extracted polysaccharides have a large relative molecular mass, mainly alginate polysaccharides. By controlling the reaction conditions, this part of the polysaccharides is preferentially extracted, and then the reaction solution is separated into solid and liquid, and the supernatant is collected by centrifugation (5000-8000r / min, 10-15 minutes).

[0045] In the second stage (2-4 hours), after adding an appropriate amount of complex enzymes and adjusting the reaction conditions (pH adjusted to 5.5-6.0, temperature increased to 50-55°C), the remaining components of the cell wall are further enzymatically hydrolyzed to release more polysaccharides with specific structures, such as fucoidan sulfate. The polysaccharides extracted in this stage have a unique sulfated modified structure and high biological activity. Solid-liquid separation is performed again, and the supernatant is collected.

[0046] In the third stage (4-6 hours), the pH of the enzymatic hydrolysis system is adjusted to 6.0-6.5, the temperature is lowered to 45°C, and the reaction time is prolonged, so that some polysaccharides tightly bound to the cell wall can be fully released. These polysaccharides may have special branching structures and biological activities. Solid-liquid separation is also performed, and the supernatant is collected.

[0047] 5. Polysaccharide separation and purification

[0048] The supernatants collected in the three stages in step 4 were combined and initially separated using ultrafiltration technology. First, an ultrafiltration membrane with a cutoff relative molecular mass of 100 kDa was used to remove impurities such as macromolecular substances and proteins that were not completely hydrolyzed. Then, the permeate was passed through an ultrafiltration membrane with a cutoff relative molecular mass of 10 kDa to further concentrate the polysaccharide solution.

[0049] The concentrated polysaccharide solution is desalted, and ion exchange chromatography is used to remove cations and anions in the solution in turn using a strongly acidic cation exchange resin and a strongly basic anion exchange resin. Afterwards, the desalted polysaccharide solution is further purified by passing it through a gel permeation chromatography column (such as Sephadex G-100, Sepharose CL-6B, etc.), and the polysaccharide molecules are separated according to their size and shape differences, and the polysaccharide solution corresponding to a single elution peak is collected.

[0050] Application Examples 1-3, Comparative Example 1

[0051] The kelp polysaccharide extracted in Example 1 was applied as a feed additive for California sea bass.

[0052] 160 California bass of similar specifications and in good health were selected and randomly divided into four groups, 40 in each group. 0.1%, 0.2%, and 0.3% of the brown algae polysaccharide feed additive of the present invention were added to the feed of the experimental groups, respectively, and they were named 0.1% group (Application Example 1), 0.2% group (Application Example 2), and 0.3% group (Application Example 3), respectively. No addition was made to the feed of the control group (Comparative Example 1). The breeding cycle was 2 months, and the breeding environment conditions remained the same. After the breeding was completed, the effect of the brown algae polysaccharide feed additive on the intestinal health of California bass was evaluated.

[0053] The effect of adding different concentrations of fucoidan feed additives on diamine oxidase in the serum of California bass was analyzed from the perspective of serum biochemical levels. The results showed that the serum diamine oxidase levels of California bass in the three groups (Application Examples 1-3) with the addition of fucoidan feed additives were all reduced, among which the serum diamine oxidase levels of California bass in the 0.2% group (Application Example 2) and the 0.3% group (Application Example 3) were significantly reduced (see Table 1), indicating that fucoidan feed additives have the ability to enhance intestinal health.

[0054] The effects of adding different concentrations of brown algae polysaccharide feed additives on the intestinal tissue morphology and related indicators of California bass were analyzed from a histological perspective. The results showed that the three groups (Application Examples 1-3) with the addition of brown algae polysaccharide feed additives changed the intestinal wall thickness, muscle layer thickness, submucosal thickness, villus height, and goblet cell number of the California bass intestine, among which the intestinal tissue morphology parameters of the 0.2% group (Application Example 2) were at the optimal level, which further confirmed that brown algae polysaccharide feed additives have the ability to enhance intestinal health.

[0055] The effects of adding different concentrations of brown algae polysaccharide feed additives on the intestinal immunity and antioxidant indicators of California bass were analyzed from the perspective of tissue biochemistry. The results showed that the three groups (Application Examples 1-3) that added brown algae polysaccharide feed additives changed the immune and antioxidant capabilities of the intestine, including C3 complement levels, lysozyme, and antioxidant enzyme-catalase. Among them, the intestinal immune ability was enhanced, mainly manifested in the significant increase in the C3 complement and lysozyme levels in the intestine of California bass in the 3% group (Application Example 3). The antioxidant capacity was enhanced, mainly manifested in the significant increase in the antioxidant enzyme levels in the intestine of California bass in the 0.1% group (Application Example 1) and the 0.2% group (Application Example 2). This also further confirms that brown algae polysaccharide feed additives have the ability to enhance intestinal health.

[0056] Table 1 Effects of feeds containing different concentrations of fucoidan on diamine oxidase in the serum of California bass

[0057] Group Diamine oxidase (ng / mL) Control group (Comparative example 1) 4.45±1.27 0.1% group (Application example 1) 3.61±0.41 0.2% group (Application example 2) 2.35±0.39* 0.3% group (Application example 3) 2.68±0.99*

[0058] Application Examples 4-6, Comparative Example 2

[0059] 140 California bass of similar specifications and good health were selected and randomly divided into four groups (Application Examples 4-6), with 35 in each group. 0.1%, 0.2%, and 0.3% of the brown algae polysaccharide feed additive of the present invention were added to the feed of the experimental groups, respectively, and they were named 0.1% group (Application Example 4), 0.2% group (Application Example 5), and 0.3% group (Application Example 6), respectively, and no addition was made to the feed of the control group (Comparative Example 2). After 2 weeks of breeding, 3% acetic acid was injected anally to induce enteritis, and samples were collected after 48 hours. The breeding environment conditions were kept consistent. After the end, the preventive effect of the brown algae polysaccharide feed additive on California bass enteritis was evaluated.

[0060] The evaluation of the effect of adding different concentrations of brown algae polysaccharide feed additives on the growth performance of California seabass enteritis was analyzed from the overall level. The results in Table 2 show that the three groups (Application Examples 4-6) with the addition of brown algae polysaccharide feed additives had a beneficial effect on the weight gain rate and body length increase rate of California seabass, especially the overall level of the 0.2% group (Application Example 5) was no different from that of the control group, which shows the preventive effect of brown algae polysaccharide feed additives on California seabass enteritis.

[0061] The effects of adding different concentrations of brown algae polysaccharide feed additives on the intestinal immunity and antioxidant indicators of California seabass enteritis were analyzed from the perspective of tissue biochemistry. The results in Table 3 show that the three groups (Application Examples 5-8) that added brown algae polysaccharide feed additives changed the intestinal immune and antioxidant capabilities, including lysozyme and antioxidant enzyme-catalase. Among them, the intestinal immune capacity did not change. The antioxidant capacity was enhanced, mainly manifested in the significant increase in the antioxidant enzyme levels in the intestines of the California seabass in the 0.1% group (Application Example 4), 0.2% group (Application Example 5) and 0.3% group (Application Example 6). This also further confirms the preventive effect of brown algae polysaccharide feed additives on California seabass enteritis.

[0062] Table 2 Effects of feeds containing different concentrations of brown algae polysaccharides on the growth performance of California bass

[0063]

[0064] Table 3 Intestinal immunity and antioxidant indexes of California sea bass enteritis in Application Examples 4-6 and Comparative Example 2

[0065]

[0066] Considering the results of Application Examples 1-6 and Comparative Examples 1-2, it was preliminarily determined that the California sea bass feed with 0.2% fucoidan added was the best for protecting the intestinal health of California sea bass. Therefore, the feed with 0.2% fucoidan added was selected to further verify the therapeutic effect of fucoidan on California sea bass enteritis.

[0067] Application Example 7, Comparative Example 3

[0068] 120 California sea bass of similar specifications and uniformly induced enteritis by anal injection of 3% acetic acid were selected and randomly divided into 20 per tank, with a total of 6 tanks, and each group had 3 tanks. 0.2% of the brown algae polysaccharide prepared in Example 1 was added to the feed of the experimental group, named as the 0.2% group (Application Example 7), and the control group was set as the enteritis group to which no brown algae polysaccharide was added to the feed (Comparative Example 3). Samples were taken after 2 weeks of feeding. The breeding environment conditions remained consistent. After the end, the therapeutic effect of the brown algae polysaccharide feed additive on California sea bass enteritis was evaluated.

[0069] The effect of adding brown algae polysaccharide feed additives on the intestinal immunity and antioxidant indicators of California sea bass induced with enteritis was analyzed from the perspective of tissue biochemistry. The results showed that the addition of brown algae polysaccharide to the three tanks of California sea bass changed the intestinal immune and antioxidant capacity, including lysozyme and antioxidant enzyme-catalase. Compared with the enteritis group (Comparative Example 3), the 0.2% group (Application Example 7) showed a decrease in lysozyme capacity and an increase in intestinal antioxidant capacity, which was mainly manifested in that the antioxidant enzyme levels in the intestines of the California sea bass in the 0.2% group were significantly increased. This confirms the therapeutic effect of brown algae polysaccharide feed additives on enteritis in California sea bass.

[0070] The effect of adding brown algae polysaccharide feed additive on intestinal immunity and antioxidant indexes of California bass induced with enteritis was analyzed from the perspective of tissue molecular level. The results in Table 4 show that the addition of brown algae polysaccharide feed additive changes the immune capacity of the intestine, including intestinal barrier molecules and immune molecules. Among them, compared with the enteritis group (Comparative Example 3), the expression of Claudin and ZO-1 molecules in the 0.2% group (Application Example 7) increased ( Figure 3 ). In addition, the intestinal immunity of the 0.2% group (Application Example 7) was enhanced, mainly manifested by the significant increase in the expression of the anti-inflammatory factor IL-10 in the intestine of the California seabass in the 0.2% group. This further confirms the therapeutic effect of the brown algae polysaccharide feed additive on California seabass enteritis.

[0071] Table 4 Biochemical indicators of intestinal immunity and antioxidation in Application Example 7 and Comparative Example 3

[0072]

[0073] Taking into account the results of Application Examples 1-7 and Comparative Examples 1-3, 0.2% of brown algae polysaccharide added as a feed additive not only protects the intestinal health of California sea bass, but also has an anti-enteritis effect.

[0074] The above disclosures are merely preferred embodiments and application examples of the present invention, and certainly cannot be used to limit the scope of rights of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope covered by the present invention.

Claims

1. A method for preparing a brown algae polysaccharide preparation, characterized in that: The following steps are involved: S1. freeze-dry the clean brown algae at -50°C to -60°C for 24-48 hours until the brown algae is dehydrated and becomes brittle, then crush the dehydrated brown algae into powder and pass through an 80-100 mesh sieve; S2. Compounding cellulase, alginate and xylanase to obtain a composite enzyme preparation; S3. The brown algae powder prepared in S1 was mixed with deionized water in a mass / volume ratio of 1:20-1:30 to form a uniform suspension, the pH was adjusted to 5.0-5.5, and then the complex enzyme preparation was added, wherein the amount of the complex enzyme preparation added was 1.0%-1.5% of the mass of the brown algae powder; S4. After S3 configuration is completed, continuous enzymatic hydrolysis is performed. The enzymatic hydrolysis process takes a total of 4-6 hours and is divided into three stages: The first stage lasts for 0-2 hours, with a pH of 5.0-5.5 and a temperature of 45-50°C. At the end of the first stage, solid-liquid separation is performed and the supernatant is collected; The second stage lasts 0-2 hours after the first stage, the pH is adjusted to 5.5-6.0, the temperature is raised to 50-55°C, and at the end of the second stage, solid-liquid separation is performed and the supernatant is collected; The third stage lasts for 0-2 hours after the second stage, the pH is adjusted to 6.0-6.5, the temperature is lowered to 45°C, and at the end of the third stage, solid-liquid separation is performed and the supernatant is collected; S5. The supernatants collected in the three stages of S4 are combined, and impurities are removed using an ultrafiltration membrane with a relative molecular weight cutoff of 100 kDa. Then, the permeate is passed through an ultrafiltration membrane with a relative molecular weight cutoff of 10 kDa to further concentrate the polysaccharide solution; S6. Desalting and purifying the concentrated polysaccharide solution prepared in S5 to obtain a brown algae polysaccharide preparation.

2. The method for preparing a brown algae polysaccharide preparation according to claim 1, characterized in that: In step S6, ion exchange chromatography is used, using strongly acidic cation exchange resin and strongly basic anion exchange resin to remove cations and anions in the solution in turn; the desalted polysaccharide solution is then purified by a gel permeation chromatography column, and the polysaccharide molecules are separated according to their size and shape differences, and the polysaccharide solution corresponding to a single elution peak is collected.

3. The method for preparing a brown algae polysaccharide preparation according to claim 1, characterized in that: In step S2, cellulase, alginate and xylanase are compounded in a mass ratio of 3:2:

1.

4. A fucoidan preparation, prepared by the method for preparing a fucoidan preparation according to any one of claims 1 to 3.

5. A feed for resisting enteritis of California sea bass, comprising the brown algae polysaccharide preparation as claimed in claim 4.

6. The feed for resisting enteritis of California sea bass according to claim 5, characterized in that: The amount of the fucoidan preparation added to the feed is 0.1-0.3% of the total mass of the feed.

7. The feed for resisting enteritis of California sea bass according to claim 5, characterized in that: The amount of the fucoidan preparation added to the feed is 0.2% of the total mass of the feed.

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