Lactobacillus fermentation extraction method of marine red algae polysaccharide and application of marine red algae polysaccharide

Abstract

The invention provides a lactobacillus fermentation extraction method of marine red algae polysaccharide and application of the marine red algae polysaccharide, and the method comprises the following steps: mixing marine red algae powder with water, and carrying out pasteurization at 60-70 DEG C for 20-40 minutes; adding lactobacillus plantarum into the sterilized marine red algae turbid liquid, and performing fermentation culture to obtain a marine red algae fermentation mixed liquid; heating and extracting the marine red algae fermentation mixed solution at 85-95 DEG C for 1.5-2.5 hours, centrifuging, collecting supernate, carrying out rotary evaporation and concentration to 1 / 5 of the original volume, then adding ethanol, standing overnight, discarding the supernate, adding distilled water into precipitate for redissolving, and deproteinizing by using a Sevag method to obtain a polysaccharide solution; and dialyzing the polysaccharide solution, and concentrating and freeze-drying the dialysate to obtain the marine red algae polysaccharide. According to the method, the low-molecular-weight modified polysaccharide is obtained through lactobacillus plantarum fermentation, extraction and purification, and the low-molecular-weight modified polysaccharide is high in sulfate group content, loose in structure, capable of remarkably inhibiting AGEs-induced intestinal cell oxidative stress and inflammatory reaction, capable of being used for preparing the glycosylation injury resisting medicine and good in industrialization prospect.

Description

Technical Field

[0001] This invention relates to the field of seaweed processing, specifically to a method for extracting polysaccharides from marine red algae using Lactobacillus fermentation and its application. Background Technology

[0002] Marine red algae (such as red hair algae, laver, agar, and Gracilaria) are characteristic economic seaweeds of southeastern coastal my country. Rich in polysaccharides, proteins, and unsaturated fatty acids, they possess various physiological functions including antioxidant, anti-inflammatory, and immunomodulatory effects. Long-term consumption of red algae can reduce the risk of cardiovascular and cerebrovascular diseases and metabolic syndrome, and has a positive effect on postprandial blood glucose control, demonstrating enormous development potential and application prospects in functional foods, pharmaceuticals, and health products.

[0003] Advanced glycation end products (AGEs) are products of non-enzymatic reactions between reducing sugars and macromolecules such as proteins. Their accumulation in the body can induce oxidative stress, inflammation, and apoptosis, leading to intestinal barrier damage and being closely related to diabetic complications and cardiovascular diseases. Therefore, exploring the mechanisms of AGEs' damaging effects on the body and finding natural inhibitors is of paramount importance.

[0004] Polysaccharides are high-molecular-weight polymers formed by more than ten monosaccharide molecules linked by glycosidic bonds, and are widely found in plants, animals, algae, and microorganisms. As important bioactive macromolecules, polysaccharides possess complex spatial structures and diverse biological activities. Their molecular weights vary widely, and their structural forms include linear, branched, and cyclic types. Existing research indicates that polysaccharide compounds possess various pharmacological activities, such as antitumor, antiviral, hypoglycemic, immunomodulatory, and anticoagulant effects. Currently, the main methods for modifying polysaccharides include physical methods (such as ultrasound and microwave) and chemical methods (such as acid hydrolysis and enzymatic hydrolysis), but these methods suffer from problems such as low modification efficiency, significant loss of active ingredients, and numerous byproducts. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in the aforementioned technologies, namely, to provide a method for extracting polysaccharides from marine red algae via lactobacillus fermentation and its application. This method involves extracting polysaccharides from marine red algae via lactobacillus fermentation, thereby enhancing the anti-glycation activity of the polysaccharides, reducing their molecular weight, optimizing their structural characteristics, and applying them to the preparation of drugs that alleviate intestinal barrier damage.

[0006] Therefore, in a first aspect of the present invention, a method for extracting polysaccharides from marine red algae by lactobacillus fermentation is provided, comprising the following steps: S1: Mix marine red algae powder with water to obtain a marine red algae suspension, and pasteurize at 60℃-70℃ for 20 min-40 min; S2: Add Lactobacillus plantarum to the marine red algae suspension sterilized in step S1, and ferment to obtain marine red algae fermentation mixture; S3: The marine red algae fermentation mixture was heated and extracted at 85℃-95℃ for 1.5 h-2.5 h, centrifuged, the supernatant was collected, concentrated by rotary evaporation to 1 / 5 of the original volume, ethanol was added, and the mixture was allowed to stand overnight. The supernatant was discarded, the precipitate was reconstituted with distilled water, and the protein was removed by the Sevag method to obtain a polysaccharide solution. S4: Dialyze the polysaccharide solution with distilled water for two days. The dialysate is then concentrated and freeze-dried to obtain marine red algae polysaccharide.

[0007] According to an embodiment of the present invention, a method for extracting marine red algae polysaccharides by lactobacillus fermentation involves treating marine red algae with *Lactobacillus plantarum* followed by extraction of the marine red algae polysaccharides. This method significantly increases the sulfate group content, decreases the molecular weight, increases the galactose content, degrades the lamellar structure into fine filaments, and enhances water solubility and the exposure rate of active groups in the extracted marine red algae polysaccharides. The protective effect of this marine red algae polysaccharide against AGEs-induced Caco-2 cell damage is superior to that of the unfermented modified group. It can reduce ROS levels, increase CAT activity and GSH levels, inhibit the release of inflammatory factors IL-8 / IL-6, and improve its ability to inhibit intestinal wall cell damage caused by advanced glycation end products (AGEs).

[0008] In addition, the method for extracting marine red algae polysaccharides by lactobacillus fermentation according to the present invention may also have the following additional technical features: Optionally, in step S1, marine red algae powder and water are mixed at a material-to-liquid ratio of 1:25-1:35 w / v.

[0009] Optionally, in step S2, the inoculation volume ratio of the *Lactobacillus plantarum* is 3%-7% v / v, and the culture conditions are constant temperature fermentation at 37°C for 40-56 h.

[0010] Optionally, in step S3, the concentration of ethanol is 70%-80%; the Sevag deproteinization method uses a mixture of chloroform and n-butanol in a ratio of 3:1 to 5:1 for deproteinization.

[0011] Optionally, in step S4, the dialysis bag has a capacity of 3000 Da-4000 Da.

[0012] In a second aspect of the present invention, a method for extracting marine red algae polysaccharides by lactobacillus fermentation is provided.

[0013] In a third aspect of the invention, the use of the above-mentioned marine red algae polysaccharide in the preparation of a medicament for alleviating AGEs-induced intestinal barrier damage is provided.

[0014] According to the application of the present invention, the marine red algae polysaccharide is obtained by fermentation, extraction and purification of Lactobacillus plantarum to obtain a low molecular weight modified polysaccharide with high sulfate content and loose structure. It can significantly inhibit AGEs-induced oxidative stress and inflammatory response in intestinal cells and can be used to prepare anti-glycation damage drugs, which has good industrialization prospects.

[0015] Optionally, the drug is used to protect against AGEs-induced intestinal damage in Caco-2 cells.

[0016] Optionally, the drug is used to reduce the levels of AGEs-induced inflammatory factors IL-8 and IL-6 in Caco-2 cells.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] Figure 1 Scanning electron microscope images of Rhodophyta polysaccharides before and after fermentation according to an embodiment of the present invention; Figure 2 Infrared spectra of Rhodophyta polysaccharides before and after fermentation according to an embodiment of the present invention; Figure 3 The effect of different concentrations of AGEs on the viability of Caco-2 cells according to embodiments of the present invention; Figure 4 The effect of BFP on Caco-2 cell viability according to an embodiment of the present invention; Figure 5 The effect of LBFP on Caco-2 cell viability according to an embodiment of the present invention; Figure 6 The effect of BFPs on the protective effect of Caco-2 cells according to embodiments of the present invention; Figure 7 The effect of BFPs on the level of the inflammatory gene (COX-2) in Caco-2 cells according to embodiments of the present invention; Figure 8 The effect of BFPs on the level of inflammatory gene (IL-1β) in Caco-2 cells according to embodiments of the present invention; Figure 9 The effect of BFP on the level of inflammatory cytokine (IL-8) in Caco-2 cells according to an embodiment of the present invention; Figure 10 The effect of BFP on the level of inflammatory cytokine (IL-6) in Caco-2 cells according to an embodiment of the present invention. Detailed Implementation

[0019] The technical solution of the present invention is illustrated below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or defining the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention.

[0020] To better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. While exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0021] The test materials used in this invention are all common commercial products and can be purchased on the market.

[0022] Lactobacillus plantarum (CICC6076) was purchased from the China Industrial Microbial Culture Collection Center.

[0023] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0024] Example 1: Extraction of polysaccharides from Rhodophyta rubrum Red algae pretreatment: Weigh 30g of red algae powder, add distilled water at a material-to-liquid ratio of 1:30 (W / V) to prepare red algae suspension, pasteurize at 65℃ for 30 min, add Lactobacillus plantarum at a volume ratio of 5% (V / V) and ferment at 37℃ for 48 h to obtain red algae fermentation mixture. Extraction of polysaccharides from *Rhodophyta rubrum*: Weigh 30g of *Rhodophyta rubrum* powder and add distilled water at a material-to-liquid ratio of 1:30 (w / v) to prepare a *Rhodophyta rubrum* suspension. Heat the *Rhodophyta rubrum* suspension and the above-mentioned *Rhodophyta rubrum* fermentation mixture separately at 90℃ for 2 h, centrifuge (4000 rpm, 20 min), collect the supernatant, and concentrate it to 1 / 5 of its original volume by rotary evaporation. Slowly add anhydrous ethanol to a final concentration of 75% (v / v) and let stand overnight. Centrifugation was used to discard the supernatant. The precipitate was reconstituted with an appropriate amount of distilled water and deproteinized using the Sevag method, which involves a mixture of chloroform and n-butanol in a 4:1 ratio. Subsequently, the polysaccharide solution was dialyzed with distilled water (3500 Da) for two days. The dialysate was concentrated and freeze-dried under strict conditions of pre-freezing to -80°C, maintaining the cold trap temperature at ≤-50°C and the vacuum degree at 5-20 Pa during the main drying stage, and undergoing programmed heating and desorption drying to prepare pre-fermentation red algae polysaccharide (BFP) and post-fermentation red algae polysaccharide (LBFP).

[0025] Example 2 Performance Test of Red Hair Algae Polysaccharide 1. Determination of the chemical composition of Rhodophyta polysaccharides: Take the BFP or LBFP obtained in the examples into centrifuge tubes, add deionized water and mix thoroughly. The total sugar content in the samples was determined using the phenol-sulfuric acid method; the protein content was determined using the Braford method; the uronic acid content was determined using the carbazole-sulfuric acid method; the sulfate group content was determined using the barium chloride-gelatin turbidimetric method; and the 3,6-lactone galactose content was determined using the resorcinol method.

[0026] The results are shown in Table 1. The total sugar content and sulfate content of the polysaccharides extracted from *Rhodotorula rubra* after fermentation with *Lactobacillus* were significantly increased. The fermentation process disrupted the cell wall and cell membrane, promoting the diffusion of polysaccharides and sulfates within the cells, while the protein content decreased significantly. These results indicate that fermentation treatment has a significant impact on the chemical composition of *Rhodotorula rubra* polysaccharides.

[0027] 2. Molecular weight: BFP and LBFP were dissolved in 0.1 M sodium chloride solution to prepare a 1 mg / mL sample solution, which was then detected using a Waters 1525 system (equipped with a binary high-pressure gradient pump and a 2414 differential refractive index detector).

[0028] The results are shown in Table 1. The molecular weight of the polysaccharide extracted from *Lactobacillus* after fermentation was significantly reduced, with BFP at 937 kDa, while LBFP after fermentation was 45 kDa. This indicates that fermentation alters the glycosidic bonds within the polysaccharide, leading to a decrease in its molecular weight. Low molecular weight polysaccharides may exhibit higher biological activity.

[0029] Table 1. Total sugar content, protein content, uronic acid content, sulfate content, 3,6-galactose content, and molecular weight of *Rhodophyta rubrum* polysaccharides before and after modification.

[0030] 3. Scanning Electron Microscopy: The surface microstructure of BFP and LBFP was observed under a scanning electron microscope. The samples were adhered to double-sided tape and uniformly sputtered with gold, and photographed at magnifications of 2000x and 5000x respectively.

[0031] The results are as follows Figure 1 As shown, A: unmodified red algae polysaccharide (2000x); B: unmodified red algae polysaccharide (5000x); C: red algae polysaccharide extracted after Lactobacillus fermentation (2000x); D: red algae polysaccharide extracted after Lactobacillus fermentation (5000x). The microstructure of the red algae polysaccharides extracted before and after Lactobacillus fermentation was observed using scanning electron microscopy. The BFP group exhibited a relatively smooth and flat surface and a compact sheet-like structure; while the sheet-like structure of LBFP was disrupted, with pores appearing on the surface, exhibiting finer filaments, which is related to its lower molecular weight. Compared to the smoother sheet-like structure of the BFP group, the loose filamentous structure can improve the solubility of the polysaccharide and facilitate the exposure of active groups. This may be because the Lactobacillus fermentation treatment disrupts the cell wall structure and decomposes the polysaccharide, resulting in an irregular filamentous morphology.

[0032] 4. Fourier Transform Infrared Spectroscopy: Changes in the molecular structure of the sample were detected using a Fourier Transform Infrared Spectrometer. BFP or LBFP was mixed with KBr powder at a ratio of 1:100, compressed into tablets, and heated at 4000-4000 cm⁻¹. -1 Within a range of 4cm -1 Scan at a resolution of [resolution value].

[0033] The results are as follows Figure 2 As shown, 3400 cm -1 The absorption peak at 2940 cm⁻¹ is caused by the stretching vibration of OH groups, while the absorption peak at 2940 cm⁻¹ is caused by the stretching vibration of OH groups. -1 The absorption peak at 1400 cm⁻¹ corresponds to the stretching vibration of CH₄. -1 The nearby absorption peaks are due to the CH angle vibration; these three absorption peaks are typical characteristic absorption peaks of polysaccharides. (1640 cm⁻¹) -1 and 1400 cm -1 The two absorption peaks indicate the presence of uronic acid in the polysaccharide; 1250 cm⁻¹ -1 The absorption peak at 890 cm⁻¹ is due to the stretching vibration of the S=O group of the sulfate group, indicating the presence of the sulfate group; -1 The characteristic absorption peak indicates the presence of a β-glycosidic bond; 760 cm⁻¹ -1 The absorption peak at that point originates from 3,6-lactone galactose.

[0034] 5. Monosaccharide composition: The monosaccharide composition of *Rhodotorula purpureus* polysaccharides was qualitatively and quantitatively analyzed using PMP derivatization. Polysaccharide samples and monosaccharide standards were subjected to PMP derivatization, extracted, purified, and then analyzed using HPLC-UV.

[0035] The results are shown in Table 2. The results indicate that BFPs are mainly composed of galactose (Gal), mannose (Man), glucose (Glc), and other monosaccharides. Galactose had the highest proportion, followed by mannose. The results show that the monosaccharide types of different BFPs did not change; processing only affected the proportion of monosaccharides in BFPs. This may be due to the different degrees to which processing induces polysaccharide chain hydrolysis and intermolecular hydrogen bond breakage. Galactose, as the main monosaccharide component of *Rhodotorula rubra* polysaccharides, showed significant differences in content among different treatment groups. The galactose content of *Rhodotorula rubra* polysaccharides extracted after Lactobacillus fermentation (92.75%) was significantly higher than that of untreated *Rhodotorula rubra* polysaccharides (91.26%).

[0036] Table 2 Monosaccharide composition of *Rhododendron molle* polysaccharides before and after modification

[0037] 6. Experiment on the effect of AGEs on Caco-2 cell viability (1) Preparation of AGEs: Bovine serum albumin and glucose were dissolved in PBS to prepare solutions with final concentrations of 20 mg / mL and 500 mM BSA-Glu, respectively. The solutions were sealed and reacted at 100℃ for 2 h. After cooling in an ice bath, the reaction solution was placed in a dialysis bag (3000 Da) and dialyzed in PBS at 4℃ for 12 h. After lyophilization, AGEs were obtained.

[0038] (2) Caco-2 cells in the logarithmic growth phase were injected with 2×10 5 Cells were seeded at different concentrations per well in 96-well plates and cultured at 37°C until they reached 85% confluence. The cell supernatant was then removed, and different concentrations of AGEs (50, 100, 200, 400, and 800 μg / mL) were added to the Caco-2 cell monolayer at a volume of 100 μL / well. The cells were then induced to grow at 37°C with 5% CO2 for 24 h. The effect of AGEs on Caco-2 cell viability was determined using the MTT assay.

[0039] The results are as follows Figure 3 As shown, treatment with different concentrations of AGEs for 24 h significantly reduced the viability of Caco-2 cells. When the AGEs concentration was 400 μg / mL, the viability of Caco-2 cells reached 76.87%. A stimulation concentration close to 80% cell viability was selected for subsequent experiments. Therefore, a stimulation concentration of 400 μg / mL of AGEs was chosen for subsequent experiments.

[0040] 7. Experiment on the effects of BFP and LBFP on Caco-2 cell viability Caco-2 cells in the logarithmic growth phase were injected with 2 × 10⁻⁶ cells. 5 Cells were seeded at different concentrations per well in 96-well plates and cultured at 37°C until they reached 85% confluence. The cell supernatant was then removed, and different concentrations of BFP or LBFP solutions (25, 50, 100, 400, and 800 μg / mL) were added to the Caco-2 cell monolayer at a volume of 100 μL / well. The cells were then induced and cultured at 37°C with 5% CO2 for 24 h. The effect of BFP or LBFP on Caco-2 cell viability was determined using the MTT assay.

[0041] The results are as follows Figure 4 and Figure 5 As shown, within the experimental concentration range of 50-800 μg / mL, the viability of Caco-2 cells in the BFPs-treated groups was above 95%, indicating that BFPs did not have significant cytotoxicity to Caco-2 cells.

[0042] 8. Experiment on the protective effect of BFP and LBFP against AGEs-induced Caco-2 cell damage. Caco-2 cells in the logarithmic growth phase were injected with 2 × 10⁻⁶ cells. 5 Cells were seeded at various concentrations in 96-well plates and cultured at 37°C until 85% confluence. The cell supernatant was then removed, and different concentrations of BFP or LBFP (25, 50, 100, and 400 μg / mL) were co-incubated with AGEs (400 μg / mL) at 37°C for 24 h. After induction culture at 37°C and 5% CO2 for 24 h, the effect of BFP or LBFP on Caco-2 activity was determined using the MTT assay.

[0043] AGEs, along with different concentrations of unmodified *Rhodophyta rubrum* polysaccharides or *Rhodophyta rubrum* polysaccharides extracted after fermentation with *Lactobacillus*, were added to a Caco-2 cell monolayer and cultured for 24 h. Figure 6 It was found that the protective effects of unmodified red algae polysaccharide (BFP) and red algae polysaccharide (LBFP) extracted after Lactobacillus fermentation on AGEs-induced Caco-2 cell damage were dose-dependent.

[0044] 9. Experiment on the effects of BFP or LBFP on the expression of inflammatory genes in Caco-2 cells. Caco-2 cells in the logarithmic growth phase were injected with 3 × 10⁻⁶ cells. 5Cells were seeded at a concentration of [specific concentration not specified] into 12-well plates and cultured at 37°C until 85% confluence. The cell supernatant was then removed, and Caco-2 cells were co-incubated with 100 μg / mL BFP or LBFP and AGEs (400 μg / mL) at 37°C for 24 h. RNA was extracted from the collected Caco-2 cells, and the expression of IL-1β and COX-2 was determined by real-time quantitative polymerase chain reaction (qPCR). The control group received no BFP or LBFP.

[0045] The results are as follows Figure 7 and Figure 8 As shown, compared with the normal control group, the relative expression levels of COX-2 and IL-1β mRNA were significantly upregulated in AGEs. Compared with AGEs, both unmodified Rhodophyta polysaccharide (BFP) and Lactobacillus fermentation-modified Rhodophyta polysaccharide (LBFP) significantly inhibited the high expression of COX-2 and IL-1β genes induced by AGEs. The results indicate that BFP and LBFP both exhibit significant activity in downregulating COX-2 and IL-1β gene expression and can effectively antagonize the AGEs-induced inflammatory response. Among them, LBFP had a significantly higher protective effect on Caco-2 cells than BFP.

[0046] 10. Experiment on the effect of BFP or LBFP on the release of inflammatory factors in Caco-2 cells. Caco-2 cells in the logarithmic growth phase were injected with 3 × 10⁻⁶ cells. 5 Cells were seeded at a concentration of [specific concentration not specified] into 12-well plates and cultured at 37°C until 85% confluence. The cell supernatant was then removed, and 100 μg / mL BFP or LBFP was co-incubated with AGEs (400 μg / mL) at 37°C for 24 h. The supernatant was then collected, and the concentrations of IL-8 and IL-6 in the cell supernatant were measured according to the ELISA kit instructions. The control group received no BFP or LBFP.

[0047] The results are as follows Figure 9 and Figure 10 As shown, compared with the normal control group, the expression levels of IL-8 and IL-6 in AGEs were significantly upregulated. Compared with AGEs, both unmodified Rhodophyta polysaccharide (BFP) and Rhodophyta polysaccharide extracted after Lactobacillus fermentation (LBFP) significantly inhibited the increase in IL-8 and IL-6 levels induced by AGEs, and the inhibitory effect of Rhodophyta polysaccharide extracted after Lactobacillus fermentation was significantly better than that of the unmodified group.

[0048] In summary, according to embodiments of the present invention, modified marine red algae polysaccharides are obtained by extracting marine red algae polysaccharides after lactobacillus fermentation. The total sugar content and sulfate content of the modified marine red algae polysaccharides are significantly increased, while the protein content and molecular weight are significantly decreased. The modified marine red algae polysaccharides have a better protective effect on Caco-2 cells than the unmodified group.

[0049] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. The illustrative expressions of the above terms in this specification should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0050] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for extracting polysaccharides from marine red algae using Lactobacillus fermentation, characterized in that, Includes the following steps: S1: Mix marine red algae powder with water to obtain a marine red algae suspension, and pasteurize at 60℃-70℃ for 20 min-40 min; S2: Add Lactobacillus plantarum to the marine red algae suspension sterilized in step S1, and ferment to obtain marine red algae fermentation mixture; S3: The marine red algae fermentation mixture was heated and extracted at 85℃-95℃ for 1.5 h-2.5 h, centrifuged, the supernatant was collected, concentrated by rotary evaporation to 1 / 5 of the original volume, ethanol was added, and the mixture was allowed to stand overnight. The supernatant was discarded, the precipitate was reconstituted with distilled water, and the protein was removed by the Sevag method to obtain a polysaccharide solution. S4: Dialyze the polysaccharide solution with distilled water for two days. The dialysate is then concentrated and freeze-dried to obtain marine red algae polysaccharide.

2. The method for extracting marine red algae polysaccharides by lactobacillus fermentation as described in claim 1, characterized in that, In step S1, marine red algae powder and water are mixed at a material-to-liquid ratio of 1:25-1:35 w / v.

3. The method for extracting marine red algae polysaccharides by lactobacillus fermentation as described in claim 1, characterized in that, In step S2, the inoculation volume ratio of Lactobacillus plantarum is 3%-7% v / v, and the culture conditions are constant temperature fermentation at 37℃ for 40-56 h.

4. The method for extracting marine red algae polysaccharides by lactobacillus fermentation as described in claim 1, characterized in that, In step S3, the concentration of ethanol is 70%-80%; the Sevag method deproteinization involves a mixture of chloroform and n-butanol in a ratio of 3:1 to 5:

1.

5. The method for extracting marine red algae polysaccharides by lactobacillus fermentation as described in claim 1, characterized in that, In step S4, the dialysis bag has a capacity of 3000 Da-4000 Da.

6. Marine red algae polysaccharides are obtained by the lactobacillus fermentation extraction method according to any one of claims 1-5.

7. The use of the marine red algae polysaccharide according to claim 6 in the preparation of a drug to alleviate AGEs-induced intestinal barrier damage.

8. The application as described in claim 7, characterized in that, The drug is used to protect against AGEs-induced intestinal damage in Caco-2 cells.

9. The application as described in claim 7, characterized in that, The drug is used to reduce the levels of IL-8 and IL-6, inflammatory factors induced by AGEs, in Caco-2 cells.

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