Method for preparing L-fucose through photocatalytic degradation and application of L-fucose in intestinal health protection

Abstract

The invention belongs to the technical field of deep processing of natural polysaccharides, and relates to a method for preparing L-fucose through photocatalytic degradation and application of the L-fucose in intestinal health protection, and the method comprises the following steps: adding a certain amount of hydrogen peroxide and a titanium dioxide photocatalyst compounded with an up-conversion luminescence agent into a fucose solution, degrading under visible light or ultraviolet light, filtering, washing, and drying to obtain the L-fucose. A degradation solution is obtained; neutralizing with catalase until no bubble is generated, decoloring, concentrating to 1 / 10 of the original volume, adding 95% ethanol with the volume 3 times that of the original volume, standing at 4 DEG C, and concentrating supernate to be in a thin syrup shape; adding 4-6 times by volume of absolute ethyl alcohol, standing at 4 DEG C, and concentrating supernate; and adding absolute ethyl alcohol, recrystallizing at 4 DEG C, and carrying out suction filtration to obtain the L-fucose. According to the method disclosed by the invention, the yield of the L-fucose is relatively high and is 5.0 to 15.0 percent; the composition can be used for repairing intestinal barriers of mice with chronic colitis and reducing release of inflammatory factors of intestinal tissues, and can be used as functional food or medicine for protecting intestinal health.

Description

Technical Field

[0001] The invention belongs to the technical field of deep processing of natural polysaccharides, and relates to an improved method for preparing L-fucose monosaccharide, and specifically to a method for preparing L-fucose by photocatalytic degradation and application thereof in protecting intestinal health. Background Art

[0002] L-fucose is a common rare sugar. In the body, L-fucose mainly exists in the non-reducing ends of glycoside chains such as glycoproteins and glycolipids and in blood group antigens. L-fucose has biological activities such as anti-cancer, anti-inflammatory, antibacterial, anti-allergic, and moisturizing, and is used in the fields of medicine, food, and cosmetics. In addition, L-fucose, as an important biochemical reagent, is used in chemical analysis, bioengineering, cell engineering, and food engineering.

[0003] The main methods for preparing L-fucose in the prior art include chemical synthesis, microbial synthesis, enzyme synthesis, and chemical or enzymatic hydrolysis of polysaccharides containing L-fucose. Among them, the chemical synthesis method usually converts common monosaccharides such as L-arabinose, D-glucose, D-mannose, D-galactose, etc. into L-fucose through a series of chemical reactions. The reaction steps are cumbersome and the yield is low, making it difficult to achieve industrial production; the microbial synthesis method is similar to the chemical synthesis method, with cumbersome steps and low yield; the enzyme synthesis method is not yet mature and is only in the process of exploration; and the chemical or enzymatic degradation method for microbial polysaccharides containing L-fucose cannot achieve efficient preparation of fucose due to factors such as the high viscosity of microbial polysaccharides and the selection of glycosidic bonds, and the method still needs to be improved.

[0004] Fucoidan is a water-soluble polysaccharide containing sulfate groups. It is a light yellow powder that is easily soluble in water. It is mainly found in brown algae such as kelp and some marine invertebrates. Fucoidan is a viscous substance secreted by brown algae cells. It is necessary for brown algae to utilize light and nutrients. Its content varies with the type of seaweed, origin, season and algal body part. At present, the comprehensive utilization research of kelp in my country mainly focuses on bulk extracts such as iodine, mannitol, and alginate. However, due to the problems of high water consumption, high energy consumption, and serious pollution in the kelp processing technology, the production costs of the three major products remain high, causing many kelp processing companies to be on the verge of small profits or losses. Extracting fucoidan from waste residues and waste liquids produced by kelp processing can effectively solve the environmental pollution problem of kelp processing industry, and also increase the high added value of kelp industry. If L-fucose can be further prepared on this basis and the existing process is optimized, it will greatly improve the utilization rate of seaweed resources, create greater economic benefits, and open up a new way for the efficient preparation of L-fucose.

[0005] Photocatalytic degradation refers to the process of using highly active free radicals generated by radiation and photocatalysts in the reaction system to degrade all organic matter into inorganic matter through processes such as addition, substitution, and electron transfer between free radicals and organic matter. Titanium dioxide has the advantages of stable chemical properties at room temperature and strong redox properties of photogenerated electrons and holes, and is widely used in the field of photocatalysis. However, titanium dioxide powder is easy to aggregate in solution, difficult to separate and recycle, and easy to form secondary pollution. Titanium dioxide has a wide bandgap and can only show its photocatalytic activity under high-energy ultraviolet light, which limits the application of titanium dioxide as a photocatalyst.

[0006] Based on the above problems, the present invention proposes a new catalyst, uses fucoidan as raw material, and optimizes the process for preparing L-fucose, thereby obtaining a new method for preparing L-fucose by photocatalytic degradation of fucoidan. Summary of the invention

[0007] The purpose of the present invention is to solve the above-mentioned problems existing in the prior art, and proposes a method for preparing L-fucose by photocatalytic degradation and its application in protecting intestinal health. Fucoidan is used as a raw material, and L-fucose is prepared by photocatalytic oxidation degradation through a titanium dioxide photocatalyst of a composite upconversion luminescent agent, thereby optimizing a simpler preparation method of L-fucose in brown algae-derived fucoidan.

[0008] The present invention optimizes the process for preparing L-fucose, and screens a simple, economical and green method for preparing L-fucose, thereby increasing the high added value of my country's seaweed industry and providing technical support for the high-value utilization of brown algae resources.

[0009] The technical solution of the present invention is:

[0010] A method for preparing L-fucose by photocatalytic degradation, characterized in that it comprises the following steps:

[0011] (1) taking a certain amount of fucoidan, adding water to dissolve it in a ratio of 1:10 to 30 to obtain a fucoidan solution, adding a certain amount of hydrogen peroxide and a titanium dioxide photocatalyst as a composite upconversion luminescent agent to the fucoidan solution, subjecting the obtained mixed solution to a degradation reaction under visible light or ultraviolet light for a reaction time of 1 to 15 hours to obtain a degradation solution;

[0012] The mass fraction of the titanium dioxide photocatalyst of the composite up-conversion luminescent agent in the mixed solution is 0.8-1.5%, and the volume fraction of hydrogen peroxide in the mixed solution is 0.5-10%.

[0013] (2) The degradation liquid is neutralized with catalase until no bubbles are generated, and activated carbon is added for decolorization to remove insoluble substances such as pigments; the decolorized solution is concentrated to 1 / 10 of the original volume, and then 3 times the volume of 95% ethanol is added, and the solution is allowed to stand at 4°C for 8 to 14 hours, and the obtained alcohol precipitation supernatant is concentrated to a thin syrup;

[0014] (3) Add 4 to 6 times the volume of anhydrous ethanol to the concentrated syrup, let it stand at 4°C for 8 to 14 hours, collect the supernatant after alcohol precipitation and concentrate it; add anhydrous ethanol, let it stand at 4°C for recrystallization, and filter it to obtain L-fucose.

[0015] Furthermore, the titanium dioxide photocatalyst of the composite upconversion luminescent agent added in step (1) is a TiO2 photocatalyst doped with an upconversion luminescent agent, and the upconversion luminescent agent is Er 3+ :YAlO3、Er 3+ :Y3Al5O 12 , Er 3+ :YAlO3 / Pt or Er 3+ :Y3Al5O 12 / Pt any one or more.

[0016] Furthermore, the titanium dioxide photocatalyst of the composite upconversion luminescent agent is doped with the upconversion luminescent agent Er 3+ :YAlO3 TiO2 photocatalyst, in which TiO2 and Er 3+ :YAlO3 mass ratio is 1 to 10:1, and the particle size of TiO2 used is 10 to 200 nm;

[0017] The titanium dioxide photocatalyst of the composite up-conversion luminescent agent is prepared by a sol-gel method, comprising the following steps:

[0018] Take Er2O3 and Y2O3 powders in a molar ratio of 1:1 and dissolve them in concentrated nitric acid, stir until a transparent solution is obtained, then add an aqueous solution of aluminum nitrate and citric acid according to a molar ratio of Y ions to Al ions of 1:1, heat and stir until a light yellow viscous gel is obtained; wherein the molar ratio of citric acid to rare earth ions is 3:1;

[0019] The obtained gel is ground into powder and calcined at 500-1500℃ to obtain Er 3+ :YAlO3 white powder;

[0020] Take tetrabutyl titanate and anhydrous ethanol, according to the tetrabutyl titanate and Er 3+ :YAlO3 was added to Er in a molar ratio of 1:1 3+ :YAlO3, let stand at room temperature for 2 to 6 hours, and Er 3+:YAlO3 TiO2 photocatalyst; wherein the liquid ratio of tetrabutyl titanate to anhydrous ethanol is 1g:30mL.

[0021] In the preparation method of the titanium dioxide photocatalyst composited with the above-mentioned upconversion luminescent agent, the upconversion luminescent agent is composited with titanium dioxide, which can convert visible light into ultraviolet light that can excite titanium dioxide; the composite catalyst broadens the absorption spectrum range of titanium dioxide and improves the visible light catalytic performance of titanium dioxide without affecting the redox performance of the generated photogenerated electron-hole pairs.

[0022] Furthermore, activated carbon is added to the degradation liquid according to a weight ratio of fucoidan to activated carbon of 100:0.05-2; the activated carbon is coconut shell activated carbon with an iodine value of 800-1200.

[0023] The present invention also provides L-fucose prepared by any of the methods described above.

[0024] The present invention also provides the use of L-fucose prepared by any of the methods described above in protecting intestinal health.

[0025] Furthermore, the L-fucose is used to improve or treat chronic colitis.

[0026] The present invention further provides the use of L-fucose prepared by any of the methods described above in the preparation of products for protecting intestinal health.

[0027] Furthermore, the product includes medicine or functional food.

[0028] Beneficial effects of the present invention:

[0029] (1) Compared with the existing disclosed methods, the preparation method of L-fucose provided by the present invention adopts a titanium dioxide photocatalyst as a composite upconversion luminescent agent to catalyze the degradation of fucoidan under visible light or ultraviolet light conditions. The operation process is simple, energy consumption is low, the preparation cost is low, the L-fucose yield is high, no toxic or harmful reagents are used, and it is more environmentally friendly.

[0030] (2) The present invention further improves the purity and yield of the L-fucose product by alcohol precipitation and crystallization; and by optimizing the alcohol precipitation conditions, the amount of ethanol is reduced while improving the purity and yield of the L-fucose product, and the use of resin columns is omitted, making the method simpler and more economical; the present invention solves the limitation of fucoidan degradation conditions and has lower requirements on equipment.

[0031] (3) The L-fucose yield of the present invention is relatively high, ranging from 5.0% to 15.0%. The prepared L-fucose can repair the intestinal barrier of mice with chronic colitis, reduce the release of inflammatory factors in intestinal tissue, and repair damaged intestinal tissue when administered intragastrically at 200 mg / kg·d. It has the effect of improving the intestinal barrier damage of mice with chronic colitis. The L-fucose can be used as a functional food or medicine alone or in combination for the development of products to protect intestinal health. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The improvement effect of L-fucose on the colon length of mice with chronic colitis;

[0033] Figure 2 The effect of L-fucose on colonic tissue pathology in mice with chronic colitis (HE staining);

[0034] Figure 3 The effect of L-fucose on colonic tissue pathology in mice with chronic colitis (AB staining);

[0035] Figure 4 The effect of L-fucose on the expression of ZO-1 in colon tissue of mice with chronic colitis;

[0036] Figure 5 The effect of L-fucose on the expression of occludin in colon tissue of mice with chronic colitis;

[0037] Figure 6 The effect of L-fucose on the expression of inflammatory factors in colon tissue of mice with chronic colitis. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] In order to further understand the present invention, the titanium dioxide photocatalyst of the present invention which is a composite up-conversion luminescent agent will be further described in conjunction with the accompanying drawings and examples.

[0040] Example 1

[0041] This embodiment provides a method for preparing L-fucose by degradation using fucoidan as a raw material, and the steps are as follows:

[0042] (1) Take a certain amount of fucoidan, add water to dissolve it in a ratio of 1 g to 30 mL to obtain a fucoidan solution;

[0043] Adding 5% by volume of hydrogen peroxide and 1.0% by mass of a titanium dioxide photocatalyst as a composite upconversion luminescent agent to the fucoidan solution, carrying out a degradation reaction under visible light or ultraviolet light irradiation for 4 hours, and fully stirring during the irradiation process to obtain a degradation solution;

[0044] (2) The degradation liquid was neutralized with catalase until no bubbles were generated, and activated carbon was added to the degradation liquid for decolorization according to a weight ratio of fucoidan to activated carbon of 100:1. The decolorized filtrate was concentrated to 1 / 10 of the original volume, and then 3 volumes of 95% ethanol were added and allowed to stand at 4°C overnight. The obtained alcohol precipitation supernatant was concentrated to a thin syrup;

[0045] (3) Add 5 times the volume of anhydrous ethanol to the concentrated syrup, let it stand at 4°C overnight, collect the supernatant after alcohol precipitation and concentrate it; add anhydrous ethanol, let it stand at 4°C for recrystallization, filter the crystals, dry them and weigh them, and the L-fucose yield is 12%.

[0046] Example 2

[0047] This embodiment provides a method for preparing a titanium dioxide photocatalyst as a composite upconversion luminescent agent by a sol-gel method, comprising the following steps:

[0048] Take Er2O3 and Y2O3 powders in a molar ratio of 1:1 and dissolve them in concentrated nitric acid, stir until a transparent solution is obtained, then add an aqueous solution of aluminum nitrate and citric acid according to a molar ratio of Y ions to Al ions of 1:1, heat and stir until a light yellow viscous gel is obtained; wherein the molar ratio of citric acid to rare earth ions is 3:1;

[0049] The obtained gel was ground into powder and then calcined at 1000℃ to obtain Er 3+ :YAlO3 white powder;

[0050] Take tetrabutyl titanate and anhydrous ethanol, according to the tetrabutyl titanate and Er 3+ :YAlO3 was added to Er in a molar ratio of 1:1 3+ :YAlO3, let stand at room temperature for 4h, and then Er 3+ :YAlO3 TiO2 photocatalyst; wherein the liquid ratio of tetrabutyl titanate to anhydrous ethanol is 1g:30mL.

[0051] Example 3

[0052] This embodiment provides a method for preparing L-fucose by using fucoidan as a raw material and degrading it through titanium dioxide photocatalyst of a composite upconversion luminescent agent, and the steps are as follows:

[0053] (1) Take a certain amount of fucoidan, add water to dissolve it in a ratio of 1 g to 10 mL to obtain a fucoidan solution;

[0054] Adding 0.5% by volume of hydrogen peroxide and 0.8% by mass of a titanium dioxide photocatalyst as a composite upconversion luminescent agent to the fucoidan solution, carrying out a degradation reaction under visible light or ultraviolet light irradiation for 1 hour, and fully stirring during the irradiation process to obtain a degradation solution;

[0055] (2) The degradation liquid was neutralized with catalase until no bubbles were generated, and activated carbon was added to the degradation liquid for decolorization according to the weight ratio of fucoidan to activated carbon of 100:0.05. The decolorized filtrate was concentrated to 1 / 10 of the original volume, and then 3 volumes of 95% ethanol were added, and the mixture was allowed to stand at 4°C overnight for 8 hours, and the obtained alcohol precipitation supernatant was concentrated to a thin syrup;

[0056] (3) Add 6 times the volume of anhydrous ethanol to the concentrated syrup, let it stand at 4°C overnight for 8 hours, collect the supernatant after alcohol precipitation and concentrate it; add anhydrous ethanol, let it stand at 4°C for recrystallization, filter the crystals, dry them and weigh them, and the L-fucose yield is 8%.

[0057] Example 4

[0058] This embodiment provides a method for preparing L-fucose by using fucoidan as a raw material and degrading it through titanium dioxide photocatalyst of a composite upconversion luminescent agent, and the steps are as follows:

[0059] (1) Take a certain amount of fucoidan and dissolve it in water at a ratio of 1 g to 20 mL to obtain a fucoidan solution;

[0060] Adding 10% hydrogen peroxide by volume and 1.5% titanium dioxide photocatalyst as a composite upconversion luminescent agent by mass into the fucoidan solution, carrying out degradation reaction under visible light or ultraviolet light irradiation for 15 hours, stirring fully during the irradiation process, and obtaining a degradation solution;

[0061] (2) The degradation liquid was neutralized with catalase until no bubbles were generated, and activated carbon was added to the degradation liquid for decolorization according to a weight ratio of fucoidan to activated carbon of 100:2. The decolorized filtrate was concentrated to 1 / 10 of the original volume, and then 3 volumes of 95% ethanol were added, and the mixture was allowed to stand at 4°C overnight for 14 hours, and the obtained alcohol precipitation supernatant was concentrated to a thin syrup;

[0062] (3) Add 4 times the volume of anhydrous ethanol to the concentrated syrup, let it stand at 4°C overnight for 12 hours, collect the supernatant after alcohol precipitation and concentrate it; add anhydrous ethanol, let it stand at 4°C for recrystallization, filter the crystals, dry them and weigh them, and the L-fucose yield is 15%.

[0063] Example 5: Effect of L-fucose on improving intestinal barrier damage in mice with chronic colitis

[0064] Experimental design

[0065] Five-week-old male C57BL / 6 mice were placed in an SPF mouse room with a temperature of 25±2°C and a light / dark cycle of 12 hours, with free access to food and water, 8 mice per cage. The mice were adaptively raised for 1 week, and the mice were divided into 3 groups, a control group (Control), a model group (Model) and an L-fucose group (FUC), wherein the L-fucose group was administered with the L-fucose prepared in Example 1. The mice in the Control group were given normal saline, and the other two groups of mice drank 2% dextran sulfate sodium (DSS) freely. The mice in the FUC group were gavaged with 200 mg / kg of L-fucose every day. The mice were weighed every other day, and the diet, drinking water and feces of the mice were observed. After the modeling was completed, the mice were fasted for 12 hours, and the mice were killed after anesthesia, and the colon tissue and contents were taken for detection.

[0066] The results are as follows Figure 1 As shown in the figure, it can be seen that the colon length of the mice in the Model group was significantly shorter than that in the Control group, while after FUC intervention, the colon length of the mice in the FUC group increased significantly, which indicates that fucose FUC can significantly improve the shortening of the colon in mice with chronic colitis.

[0067] HE staining

[0068] The colon tissue was immersed in 4% paraformaldehyde solution and fixed for 24 hours, then dehydrated and paraffin-embedded, and cut into 3-4 μm thick paraffin sections, and HE staining was performed according to the following steps.

[0069] (1) Dewaxing of paraffin sections: Dewax the sections with xylene I for 20 min, dewax with xylene II for 20 min, soak in anhydrous ethanol I for 5 min, soak in anhydrous ethanol II for 5 min, soak in 75% alcohol for 5 min, and wash with tap water. (2) Hematoxylin staining: Soak the sections in hematoxylin staining solution for 3-5 min, wash with tap water, reverse blue with bluing solution, and rinse with running water. (3) Eosin staining: Dehydrate the sections with 85% ethanol and 95% ethanol for 5 min, and then soak in eosin staining solution for 5 min. (4) Dehydration and sealing: Soak the sections in anhydrous ethanol I for 5 min, anhydrous ethanol II for 5 min, anhydrous ethanol III for 5 min, xylene I for 5 min, xylene II for 5 min, and finally seal the sections with neutral gum. Observe under a microscope.

[0070] like Figure 2As shown in the figure, compared with normal mice, DSS can cause pathological damage to colon tissue, such as inflammatory infiltration of colon epithelial cells and destruction of crypt structure, while after FUC intervention, the colon tissue morphology was significantly improved. This shows that FUC can significantly repair colon tissue damage.

[0071] Immunohistochemistry (IHC)

[0072] The IHC method was used to observe the expression of tight junction proteins ZO-1 and occludin in colon tissue. The colon tissue was fixed with 4% neutral buffered formalin and embedded for 24 hours. Sections of about 2 μm thickness were taken from the tissue block for immunohistochemistry. The sections were placed on a slide, dewaxed in xylene, and then rehydrated with graded ethanol. Then, they were incubated in a 3% H2O2 solution for 25 minutes, and antigen retrieval was performed in a 95°C citrate buffer for 7.5 minutes. The prepared samples were incubated with the corresponding primary antibody at 4°C overnight, and then incubated with the secondary antibody for 45 minutes. Finally, the protein expression was observed by staining with diaminobenzidine (DAB).

[0073] like Figure 3 As shown in the figure, compared with the normal group mice, the amount of acidic mucin in the colon tissue of the Model group mice was significantly reduced, while after FUC intervention, the expression of acidic mucin in the colon tissue of the mice was significantly increased, which indicates that FUC can protect the intestinal mucus barrier of mice by promoting the expression of acidic mucin.

[0074] like Figure 4 As shown in the figure, it can be seen that DSS can significantly reduce the expression of tight junction protein ZO-1 in mouse colon tissue, while FUC can significantly improve the level of ZO-1 and promote its expression. This shows that FUC can improve the intestinal barrier by promoting the expression of ZO-1.

[0075] like Figure 5 As shown in the figure, it can be seen that DSS can significantly reduce the expression of tight junction protein occludin in mouse colon tissue, while FUC can significantly improve the level of ZO-1 and promote its expression. This shows that FUC can improve the intestinal barrier by promoting the expression of occludin.

[0076] Inflammatory factor assay

[0077] Colon tissue was taken and sterile PBS was added at a ratio of 1:9 (w / v) and fully ground. The resulting homogenate was centrifuged at 4°C and 10,000 rpm for 10 min, and the supernatant was collected for subsequent determination. The contents of TNF-α, IL-1β, and IL-10 in mouse colon tissue were detected using an enzyme-linked immunosorbent assay (ELISA) kit according to the kit instructions.

[0078] The results are as follows Figure 6 As shown in the figure, compared with normal mice, the expression of pro-inflammatory factors TNF-α, IL-1β and IFN-γ in the colon tissue of the model group mice was significantly increased, while the expression of anti-inflammatory factor IL-10 was significantly decreased. After FUC intervention, the pro-inflammatory factors in the colon tissue of mice were significantly reduced, while the anti-inflammatory factors were significantly increased. This shows that fucose can significantly reduce the inflammatory damage of the colon in colitis mice.

[0079] The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments, or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, modification, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing L-fucose by photocatalytic degradation, characterized in that: The following steps are involved: (1) taking a certain amount of fucoidan, adding water to dissolve it in a ratio of 1:10 to 30 to obtain a fucoidan solution, adding a certain amount of hydrogen peroxide and a titanium dioxide photocatalyst as a composite upconversion luminescent agent to the fucoidan solution, subjecting the obtained mixed solution to a degradation reaction under visible light or ultraviolet light for a reaction time of 1 to 15 hours to obtain a degradation solution; The mass fraction of the titanium dioxide photocatalyst of the composite up-conversion luminescent agent in the mixed solution is 0.8-1.5%, and the volume fraction of hydrogen peroxide in the mixed solution is 0.5-10%. (2) The degradation solution is neutralized with catalase until no bubbles are generated, activated carbon is added for decolorization, the decolorized solution is concentrated to 1 / 10 of the original volume, and then 3 times the volume of 95% ethanol is added, and the solution is allowed to stand at 4°C for 8 to 14 hours, and the obtained alcohol precipitation supernatant is concentrated to a thin syrup; (3) Add 4 to 6 times the volume of anhydrous ethanol to the concentrated syrup, let it stand at 4°C for 8 to 14 hours, collect the supernatant after alcohol precipitation and concentrate it; add anhydrous ethanol, let it stand at 4°C for recrystallization, and filter it to obtain L-fucose.

2. The method according to claim 1, characterized in that The titanium dioxide photocatalyst of the composite upconversion luminescent agent added in step (1) is a TiO2 photocatalyst doped with an upconversion luminescent agent, and the upconversion luminescent agent is Er 3+ :YAlO3、Er 3 + :Y3Al5O 12 , Er 3+ :YAlO3 / Pt or Er 3+ :Y3Al5O 12 / Pt any one or more.

3. The method according to claim 1, characterized in that The titanium dioxide photocatalyst of the composite up-conversion luminescent agent is doped with the up-conversion luminescent agent Er 3+ :YAlO3 TiO2 photocatalyst, in which TiO2 and Er 3+ :YAlO3 mass ratio is 1 to 10:1, and the particle size of TiO2 used is 10 to 200 nm; The titanium dioxide photocatalyst of the composite up-conversion luminescent agent is prepared by a sol-gel method, comprising the following steps: Take Er2O3 and Y2O3 powders in a molar ratio of 1:1 and dissolve them in concentrated nitric acid, stir until a transparent solution is obtained, then add an aqueous solution of aluminum nitrate and citric acid according to a molar ratio of Y ions to Al ions of 1:1, heat and stir until a light yellow viscous gel is obtained; wherein the molar ratio of citric acid to rare earth ions is 3:1; The obtained gel is ground into powder and calcined at 500-1500℃ to obtain Er 3+ :YAlO3 white powder; Take tetrabutyl titanate and anhydrous ethanol, according to the tetrabutyl titanate and Er 3+ :YAlO3 was added to Er in a molar ratio of 1:1 3+ :YAlO3, let stand at room temperature for 2 to 6 hours, and Er 3+ :YAlO3 TiO2 photocatalyst; wherein the liquid ratio of tetrabutyl titanate to anhydrous ethanol is 1g:30mL.

4. The method according to claim 1, characterized in that Activated carbon is added to the degradation liquid according to a weight ratio of fucoidan to activated carbon of 100:0.05-2; the activated carbon is coconut shell activated carbon with an iodine value of 800-1200.

5. L-fucose prepared by the method according to any one of claims 1 to 4.

6. Use of L-fucose prepared by the method according to any one of claims 1 to 4 in protecting intestinal health.

7. The use according to claim 6, characterized in that: The L-fucose is used for improving or treating chronic colitis.

8. Use of L-fucose prepared by the method according to any one of claims 1 to 4 in preparing products for protecting intestinal health.

9. The use according to claim 8, characterized in that: The products include medicines or functional foods.

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