Screening Of Antioxidative Lactic Acid Bacteria

Oxidation is essential for living organisms`life activities,but oxidative stress,occurred with abnormally high levels of reactive oxygen species (ROS), which can damage biological molecules and plays a significant pathological role in human disease. The native antioxidative systems in organisms are not enough to prevent them from the oxidative damage. The addition of antioxidant may be a suitable choice to help reduction of oxidative damage. Among many kinds of antioxidants, natural antioxidants are more desirable. Lactic acid bacteria (LAB) are food grade bacteria with a GRAS (generally regarded as safe) status, which are widely used in food fermentation. I t`s well know that LAB has potential benefits for human health. However, the researches on the antioxidative activity of LAB are reported only in recent years.Two strains of lactic acid bacteria were isolated from different fermented foods based on the in vitro resistance to hydrogen peroxide. Free raidical-Scavenging ability of two isolates were studied. The results showed that, theα,α-diphenyl-β-picrylhydrazyl (DPPH·) free radical-scavenging ratio by intact cells and cell-free extracts of a L1001109 cfu/m1 lactic acid bacteria were 36.2% and 37.9% respectively, and those of 109cfu/mL F12 cell suspension and cell-free extracts were 24.4% and 27.0%, respectively; The hydroxyl radicals-eliminating ability of 109cfu/mL cells were equivalent to that of 1mmol/L ascorbic acid of the same volume.The physiological characteristics of strain L1001 were studied. The optimal growth temperature was 35℃-37℃. As for initial pH value for cell growth, the optimal value was 6.0, and the upper and lower limit of pH were 9.5 and 3.8, respectively. Strains L1001 has a relatively short delay period and enters the logarithmic growth phase after 4 hours and reached stationary period after l2 hours. The strain of L1001 was identified as Lactobacillus plantarum L1001 based on the API method.Further study showed that the superoxide dismutase activity was found in the cell-free extracts of L. plantarum L1001(1.20±0.26U/mL), and the glutathione peroxidase activity is 54.94±12.54 vitality units. And data also indicated that the SOD activity of L. plantarum L1001 is not significantly affected by oxygen concentrations. Through the study of the SOD biomass at different stages,we found that the SOD is induced at the end of exponenary period in L. plantarum L1001. manganese ions and the concentration of sodium selenite in the medium have a certain influence on the antioxidant activity of L. plantarum L1001.Higher antioxidant activity of lactic acid bacteria in vivo was studied.The activity of antioxidase system enzymes,superoxide dismutase(SOD),catalase(CAT),glutathiine peroxidase(GSH-Px)and MDA of blood in rats were tested concluding five experimental treatment,the control,the ascorbic acid control,and L .plantarum L1001.It is seemed that the ascorbic acid and L. plantarum L1001 can increased the SOD,GSH-Px and CAT activity and decreased MDA concents in blood of rats.