Study On The Structure,Digestive Characteristics And Colitis Inhibition Effect Of Polysaccharides From Lyophyllum Decastes

As a kind of bioactive component,edible mushroom polysaccharide can play a role in reducing blood glucose and lipid,alleviating inflammation,regulating gut microbiota and so on.Lyophyllum decastes is a precious fungus for medicine and food,belonging to the order of Umbelliferae,Lyophyllum genus.At present,the study on the digestive characteristics and the specific physiological activities of polysaccharides from Lyophyllum decastes(LDPS)is relatively lacking.In addition,more and more studies began to focus on the interaction between polysaccharide and gut microbiota,as well as the biological activity effect based on flora regulation.LDPS is the object of this study,optimization of LDPS extraction process by single factor and response surface test,and analyzes its structural characteristics;explores the characteristics of LDPS in vitro digestion and fermentation and the interaction with gut microbiota through the construction of in vitro digestion and fermentation model;constructs the colitis animal model studies the inhibition effect and mechanism of LDPS on colitis.The following is the research content and results:1.Optimization of LDPS extraction process and analysis of structure characteristicsThe extraction temperature,extraction time,ration of water to material and extraction times were selected as the influencing factors.Single factor and response surface optimization tests were used to obtain the optimal extraction process parameters of LDPS:extraction temperature 89?,extraction for 3 hours,ration of water to material 30:1(mL/g),extraction for 2 times,the maximum yield of polysaccharide was 5.35%±0.12%.We found that the total sugar content was 74.30%,protein content was 6.63%,glucuronic acid content was 57.06%,sulfuric acid content was 0.65%,polyphenol content was 1.10%.The results showed that the average molecular weight of polysaccharide was 1792.5 ± 40.3 kDa,which was ?-configuration polysaccharide.It was composed of mannose,ribose,rhamnose,galacturonic acid,glucose,galactose,arabinose and fucose.The mole numbers of glucose and galactose accounted for a large proportion.The research results of rheological properties show that the apparent viscosity of polysaccharides increased with the increase of concentration and decreased with the increase of temperature;the apparent viscosity of polysaccharides was larger under the conditions of pH 3,pH 7 and pH 9;as the NaCl concentration increases,the apparent viscosity of polysaccharides increases first and then decreases.When NaCl concentration was 0.1 M,the apparent viscosity of polysaccharides was the largest.2.Study on the digestive characteristics of LDPS and the regulation of Intestinal MicroecologyThe digestion characteristics of polysaccharides in saliva,gastric juice and gastrointestinal juice were studied by constructing an in vitro digestion model.The results showed that during the digestion of saliva and gastric juice,the molecular weight of LDPS,the content of reducing sugar and free monosaccharide in the digestive juice had no significant change,indicating that LDPS was not affected by the digestion of saliva and gastric juice.There was no significant change in molecular weight and free monosaccharide formation in the digestive process of gastrointestinal fluid,but the content of reducing sugar increased significantly after 6 hours of digestion,which indicated that the polysaccharide was slightly degraded.The interaction between LDPS and gut microbiota was studied by establishing an in vitro anaerobic fermentation model of human feces and using high-throughput sequencing technology.The results showed that with the prolongation of fermentation time,the pH value of the fermentation broth of LDPS group decreased significantly,the content of polysaccharide decreased,the content of reducing sugar and free monosaccharide increased first and then decreased,and the retention rate of carbohydrate decreased,which indicated that the polysaccharide entered the colon and was decomposed and utilized by gut microbiota.In addition,LDPS significantly reduced the proportion of Firmicutes/Bacteroides,and significantly increased the relative abundance of Ruminococcus,Fuscatinibacter and Lactobacillus.It is suggested that LDPS can regulate gut microbiota.3.Effect of LDPS on DSS induced colitis and gut microbiota.The mouse model of C57BL/6 colitis was constructed with sodium dextran sulfate(DSS)to evaluate the effects of low,medium and high doses(LLDPS 200 mg/kg/d?MLDPS 400 mg/kg/d?HLDPS 800 mg/kg/d)of polysaccharide solution on colitis mice and gut microbiota.The results showed that LDPS could alleviate the decrease of body weight and drinking water diet of mice caused by DSS,and significantly inhibit the decrease of solid fecal mass,the increase of fecal heme content,disease activity index(DAI),and the shortening of colon.Among them,MLDPS and HLDPS had better effects.qRT-PCR was used to detect the expression of inflammatory factors and related genes.It was found that MLDPS could significantly reduce the content and expression levels of inflammatory factors,and significantly increase the expression levels of tight junction protein ZO-1,Occludin and Claudin-1 mRNA.In the LLDPS,MLDPS and HLDPS groups,the bacteria with significant increase in relative abundance were respectively Butyricimonas,Romboutsia;Lactobacillus_johnsonii_FI9785 Prevotellaceae;Lactobacillus_animalis.In addition,LDPS could significantly reduce the relative abundance of Ruminococcaceae and Deferribacteraceae at the family level.In conclusion,LDPS can improve DSS induced colitis by regulating intestinal flora,but the specific mechanism needs further study.