Study On Physicochemical Properties And Weight Loss Activity Of Sea Cucumber Waste Polysaccharide

Sea cucumbers are rich in biologically active substances,have the nutritional properties of low sugar,low fat,high protein,and high dietary fiber,and have a variety of biological activities,which have attracted much attention from researchers in recent years.Sea fields produce a lot of waste,which contains many active ingredients.Still,it has not been fully utilized due to lack of research,resulting in waste of precious resources and environmental pollution.Based on this,this thesis took sea cucumber industrial waste as raw material,extracted and separated sea cucumber polysaccharides,and studied its structure,physicochemical properties,and weight loss activity.A single factor experiment surface methodology studied the optimal extraction conditions of sea cucumber polysaccharides.Cellulose DEAE-52 chromatography and column and Sepharose 4B chromatographic columns separated and purified sea cucumber polysaccharides.The results showed that the optimal extraction conditions were 81.7℃,extracting twice,1.16 h each time.The extraction yield was 4.26%±0.11%;after chromatographic column separation and purification,three polysaccharide components were obtained,namely sea cucumber polysaccharide I(SCIP-I),sea cucumber polysaccharide(SCIP-II),and sea cucumber polysaccharide III(SCIP-III),of which SCIP-III accounted for the highest proportion.The composition,structure,and physicochemical properties of SCIP-III were studied by chemical analysis methods combined with instrumental analysis methods such as HPLC,GC,FT-IR,NMR,SEM,AFM,TGA,DSC,and microrheometer.The results showed that the total sugar and protein contents of SCIP-III were 82.20%and 6.34%,respectively,which consisted of mannose,arabinose,galactose,glucose,and fucose(22.03:19.31:11.78:3.22:42.57 in mole percentages).Its Mw is 4.91×10~6Da,and its polydispersity index(Mw/Mn)is 1.02.β-glycosidic bonds connect its monosaccharide residues.SCIP-III is an oval particle in the SEM image,consistent with different sized,spherically structured,and aggregated molecules under AFM detection results.DSC test results showed that SCIP-III had two significant peaks.With Tp andΔH of 89.12℃ and-68.18 J/g,the first peak is caused by losing water.The second peak,with Tp andΔH of 193.87°C and-70.84 J/g,indicates the decomposing of SCIP-III.In the thermogravimetric analysis results,there are weight loss peaks of bound water and free water loss at 30-130℃,and there are polysaccharide glycosidic bonds and sugars at 200-400℃.Weight loss peaks for ring structure disruption;the fluidity,elasticity,and viscosity of SCIP-III solutions decrease with increasing concentration.A high-fat diet was used to establish an obese mouse model to study the weight loss effect of sea cucumber polysaccharides(SCIPs).The results showed that the SCIPs dose group could significantly inhibit the weight gain in obese mice.Significantly reduced the fat index,adipocyte size,and blood lipid level(p<0.05),significantly reduced the serum LPS content,and improved the experimental glucose tolerance of mice.In addition,SCIPs can significantly increase the intestinal short-chain fatty acid content of experimental mice(p<0.05)and can raise triglyceride lipase(ATGL),hormone-sensitive lipase(HSL),acetyl coenzyme acetylase 1(ACC1),interleukin-6(Il-6)m RNA content(p<0.05)substantially.The results of the intestinal microbiota analysis showed that administration of SCIPs can modify the relative abundances of Firmicutes,Proteobacteria,and Bacteroidetes.The Firmicutes/Bacteroidetes ratio increased from 1.2 in NC group to1.45 in HFD group.Administration of SCIPs,the Firmicutes/Bacteroidetes ratios were 0.87,1.3,and 0.95 in LSCIP,MSCIP and HSCIP groups,respectively.In addition,SCIPs administration could reduce the relative abundance of harmful thick cell walled bacteria such as Desulfovibro,Bifidobacterium,Parvibacter,Enterorhabdus and increase the diversity of beneficial intestinal flora such as Bacteroides,Lactobacillus,Faecalibaculum,and Lachnospiraceae,which contributed to the fermentation of dietary undigested bioactive lipids.The above results demonstrate that SCIPs can achieve lipid-lowering and weight-loss effects by regulating the expression of enzymes and cytokines related to lipid metabolism as well as gut microbiota compositions.