Screening And Reaction Mechanism Of Lactic Acid Bacteria Inhibitong Of Samonella

Lactic acid bacteria(LAB)plays an important role in keeping human intestinal flora balance and improving human health.Good tolerance to the intestinal environment and adhesion to the gastrointestinal mucosa is the prerequisite for lactic acid bacteria to exert their health-promoting activities.Therefore,tolerance and adhesive ability are considered as two selection criteria for probiotic LAB strains.Studies on the adhesive properties and mechanisms of lactic acid bacteria are of significant importance not only to the improvement of microbial eco-system in the gastrointestinal tract and biotherapeutic control of entero-pathogens.In this paper,90 different lactic acid bacteria strains isolated from traditional fermented foods were evaluated and screened for their resistance and adhesive properties to the gastrointestinal tract.And the adhesive mechanism of one Pediococcuspentosaceus was studied.Results are as follows:Firstly,according to the well-diffusion assay,90 lactic acid bacteria isolated and purified from different sources of traditional fermented foods were screened for antimicrobial activity against Salmonella,Staphylococcus aureus,Escherichia coli and Pseudomonas aeruginosa,18 LAB strains were found with high level of antimicrobial activity.Meanwhile,the resistance ability to the simulated gastrointestinal tract environment was evaluated.There is significant difference of tolerance among different strains.The strains Pediococcus pentosaceus SR2-6,Lactobacillus plantarumR2,Enterococcus faecalis5-5 andLactobacillus plantarum 3-4 showed good antimicrobial activity to four pathogens and P.pentosaceusSR2-6,L.plantarumR2,L.plantarumAB1 showed high tolerance to the simulated gastrointestinal tract environment.All the 18 strains were identified.Secondly,using Caco-2 as a cell model,the surface properties including aggregation,hydrophobicity and adhesion of city 18 LAB strains were measured,P.pentosaceusSR2-6 and L.plantarum R2 were screened with their good tolerance to gastrointestinal fluids and high adhesion to Caco-2 cells.P.pentosaceusSR2-6 showed lower damage to Caco-2 cell membrane and high inhibition of Salmonella adhere to Caco-2 cell,making it as the object in the following research.Finally,the mechanism of the adhesion of P.pentosaceusSR2-6 was investigated by different chemical and enzymatic treatments and the macromolecules involved in the adhesion were extracted.The results showed that,P.pentosaceusSR2-6 can significantly up-regulated MUC3 gene expression in Caco-2 cells and peptidoglycan of SR2-6 exerted the main role in the adhesion processes.Peptidoglycan of P.pentosaceusSR2-6,demonstrated as the ?-type,were mainly composed of glutamic acid,malonic acid,aspartic acid and lysine,having a total sugar content of(9.42 ± 1.55)%;protein content of(4.61 ± 1.88)%.P.pentosaceusSR2-6 peptidoglycan extraction was an inhibitory adhesin,the higher the concentration,the stronger inhibition of P.pentosaceus SR2-6 and Salmonella adhesion and the higher degree of upregulating of the expression of gene MUC3.