Study Of Lactobacillus Extracellular Polysaccharide Antioxidant Activity

The organism constantly produces free radicals in normal metabolism.Excessive release of free radicals leads to the accumulation of free radicals.Studies have shown that lactic acid bacteria extracellular polysaccharide has significant antioxidant activity,Therefore,it has gradually become a class of substances that can replace synthetic antioxidants.In this experiment,a strain producing high antioxidant active polysaccharide was screened from 8strains of extracellular polysaccharide-producing Lactobacillus.The oxidation resistance was evaluated and its structure was initially analyzed.First,EPS was extracted from the MRS culture medium of 8 strains of Lactobacillus casei Y3,L.casei Y4,L.casei Y16,Lactobacillus planterum Y41,L.planterum Y42,L.planterum Y44,L.casei Y35,Lactobacillus rhamnosus GG,and extracting polysaccharides by alcohol precipitation-water extraction.By measuring the DPPH free radical scavenging rate,ABTS·clearance rate,hydroxyl radical scavenging rate,iron ion reducing power(FRAP),oxygen radical absorption capacity(ORAC)and the protective effect of ABAP on oxidative damage of HT-29 cells.Principal component analysis was used to screen for strains producing high antioxidant activity EPS.The highest score of EPS antioxidant activity of Y42 strain was obtained by principal component analysis.The extracellular polysaccharide produced by Y42 strain had the strongest antioxidant activity.Therefore,the EPS produced by Y42 strain was selected for subsequent experiments.EPS produced by Y42 strains at concentrations of 500 ?g/mL,250 ?g/mL,100 ?g/mL,and 50 ?g/mL was applied to ABA-29 cells damaged by ABAP.The results show that as the concentration of exopolysaccharide decreases,The survival rate of oxidative damage to HT-29 cells gradually decreased.However,they were significantly higher than the oxidative injury group(p<0.05).It was found that Y42 strain EPS significantly up-regulated the expression of catalase(CAT)and superoxide dismutase(SOD)in HT-29 cells(p<0.05).The activity of glutathione peroxidase(GSH-Px)in the cells was also significantly higher than that in the oxidized group(p<0.05).Finally,the DE42-Sepharose Fast Flow ion column was used to separate and purify the Y42 crude polysaccharide,and two components were obtained,which were 42-1 neutral polysaccharide and 42-2 acidic polysaccharide.The monosaccharide composition of Y42 crude polysaccharide was determined by high performance liquid chromatography.The monosaccharide composition of Y42 crude polysaccharide was determined by high performance liquid chromatography as mannose,glucuronic acid,glucosamine,galactose,galactose,and their molar ratio was 11.30:3.51:10.64.Infrared spectroscopy scanning of Y42 crude polysaccharide showed that the sugar has a typical characteristic absorption peak and belongs to the skeleton mode of pyranose ring.According to the experimental results,L.planterum Y42 exopolysaccharide may protect HT-29 cells from ABAP free radical damage by scavenging oxygen free radicals and promoting the expression of antioxidant enzymes in HT-29 cells.