Screening Of Lactobacillus Producing Exopolysaccharide And The Exopolysaccharide Function Study

Most of lactic acid bacteria(LAB)produce exopolysaccharides(EPS),a kind of unique long-chain polysaccharide.LAB are generally regarded as safe(GRAS)microorganisms,Moreover,LAB EPS may provide health benefits.EPS obtained from Lactobacillusis are search hot spot.This studyof the work was to study on screening and functionofLactobacillus plantarum high-yielding exopolysaccharideand purify EPS and to investigate the molecular weight of the EPS.To screen the higher EPS yielding strains,the EPS yield were measured.Lactobacillus plantarum-12?49?50 could produce higer EPS(589.21±3.12mg/L?631.10±5.26mg/L?617.32±10.07mg/L)in the same fermental conditions than others.So their EPS were obtained from the fermented strains for further study.To study the antioxidant activities of EPS from three Lactobacillus,DPPH radical scavenging were measured as antioxidant activity.Results showed that the scavenging ability against DPPH of EPS at 0.50 mg/mL and 0.30 mg/mL were 48.82±3.88%and 28.33±5.71%.EPS could inhibit the ability of pathogenic E.coli ATCC25922 to adhere tointestinal HT-29 cells through exclude inhibition.Comprehensive analysis,the EPS of Lactobacillus plantarum-12 have better ability.The inhibitory rate were 78.23%.We studied the actions of EPS of Lactobacillus plantarum-12 in inhibiting E·coli ATCC25922 to stimulate HT-29 cell secreting IL-8 and IL-10,which indicated that EPS inhibit IL-8,with the suppression ratio of 42.5%.The results showed that Lactobacillus plantarum-12 had the higher EPS yielding,which were potential probiotic function.Through the screening experiments,Lactobacillus plantarum-12 were obtained.Through removing the bacteria cells and proteins,the crude EPS were obtained from the fermented strains.Purified the EPS produced by the rescreening strain with a DEAE-Sepharose Fast Flow ion-exchange chromatographycolumn and gel exclusion chromatography.Two fractions of EPS were obtained,EPS 1 a fris tone and EPS2 an second one.The fraction EPS2 were purified by the Sepharose Cl-6B gelfiltration chromatography.and frist EPS1 were purified by Sephacryl HR S200,respectively.By the Standard curve for determining Mw of polysaccharide analysis showed that two polysaccharide has high purity,and the molecular weight of two fractions were 8.5 X 104Da and 7.4 × 10~4Da determined by the Standard curve for determining Mw of polysaccharide.The results showed that Lactobacillus plantarum-12 hadthe higher EPS yielding,which were potential probiotic function.Purified the EPS and determined the molecular weight of two fractions of EPS,which were the basic research.