Metabolic And Biochemical Responses Of Lactobacillus Kefiranofaciens ZW3to Oxygen

Lactic acid bacteria are a kind of long term applied in food fermentation, bio pharmaceutical industry and are recognized as a food grade safety microorganism. However, the vast majority of lactic acid bacteria are anaerobic bacteria, their sensitivity to oxygen and lower survival rate, limiting their probiotic functions. The cause of low survival ability of lactic acid bacteria, toxic effects of oxygen is considered a very important factor. This paper has studied the influence of oxygen on Lactobacillus kefiranofaciens ZW3metabolism and biochemical characteristics, and clarify the bacteria oxidative stress reaction mechanism Preliminary, laid the theoretical foundation for the application of the strain in industrial production.The experiment is based on the complete genome sequence of Lactobacillus kefiranofaciens ZW3, using bioinformatics methods, analysis its aerobic respiration metabolism related genes, find that it is equipped with some genetic elements required for aerobic respiration:cydA,cydB and noxB gene, but lack the gene for hemoglobin and quinone biosynthesis, so the bacteria cannot conduct aerobic respiration in natural conditions.The experimental has studied the influence of oxygen on metabolism and biochemical characteristics of Lactobacillus kefiranofaciens ZW3and oxidative stress mechanism, determination of growth curve of the bacteria in both aerobic and anaerobic conditions, show that although the bacteria do not have complete aerobic respiratory chain, still can. obtain certain growth under aerobic conditions. H2O2accumulation in the medium under anaerobic and different concentration oxygen conditions were measured, show that under aerobic condition, H2O2may be the main substance to inhibit the bacteria growth. At the same time, the effect of oxygen on the fermentation products of lactic acid and acetic acid were measured, results show that lactic acid production rise and acetic acid production falling. Superoxide dismutase, NADH oxidase and NADH peroxidase activities were measured, the results showed that SOD activity of this strain is very low, and the difference in activity under anaerobic conditions and different oxygen concentrations of the enzyme is not notable. NADH oxidase and NADH peroxidase activities increased gradually while the oxygen concentration in the environment is increasing.In this experiment, Lactobacillus plantarum299used as a reference, which can be well grown in aerobic environments, Superoxide dismutase activities, H2O2accumulation in the medium under anaerobic and different concentration oxygen conditions, NADH oxidase and NADH peroxidase activities of this strain were measured. The results showed that there is no H2O2accumulation in the medium under aerobic condition, and the difference of Superoxide dismutase activities between this strain and Lactobacillus kefiranofaciens ZW3was not notable,however, NADH oxidase and NADH peroxidase activity was significantly higher than Lactobacillus kefiranofaciens ZW3, and activities of these two enzymes increased significantly while the oxygen concentration in the environment is increasing. Therefore, we conclude that:NADH oxidase and NADH peroxidase play an important role in oxidative stress of Lactobacillus kefiranofaciens ZW3.