Study on antioxidant activity and acid, bile salts tolerance of lactic acid bacteria

The antioxidant capabilities of 25 lactic acid bacteria in vitro from intact cells, cell-free extracts were evaluated through scavenging DPPH free radicals and reducing activities methods. The 25 strains of 10 strains lactic acid bacteria with higher antioxidant activities were further studied, acid and bile salt tolerance were researched by stimulating human gastric acid and intestinal bile salt condition. In order to provide theoretical foundation for developing functional food, lactic acid bacteria with antioxidant activity and acid and bile salt tolerance activity were compared in this paper. Different genera and different strains of the same genus of lactic acid bacteria exhibited different antioxidant activity and acid and bile salts tolerance, antioxidant places also exhibited different antioxidant activities. L. caseiGL-2 displayed the excellent antioxidant activity and acid and bile salt tolerance among 25 lactic acid bacterial strains.The result showed that the scavenging DPPH free radical of intact cells and cell-free extracts of L.caseiGL-2 were 37.22% and 42.78% respectively when its biomass concentration was 109cfu/mL, the reduced activity was equivalent to 104.84μmol/L and 107.10μmol/L that of L-cysteine, after treated with pH3.0 acid buffer solution for 2h, the survival rate of L. caseiGL-2 was 100%, in the MRS medium containing bile salt 0.5% (W/V) , the survival rate of L. caseiGL-2 was 0.35%.