Antioxidative properties of Lactobacillus sake upon exposure to elevated oxygen concentrations.

The ability of bacteria to overcome oxidative stress is related to the levels and types of antioxidative mechanisms which they possess. In this study, the antioxidative properties in Lactobacillus sake strains from different food origins were determined at low temperature (8°C) and upon exposure to oxygen levels between 20 and 90% O2. The L. sake strains tested grew well at 8°C and in the presence of 20% O2, however, most of the strains could not grow at O2 levels as high as 50 and/or 90%. Cell-free extracts of all strains possessed certain levels of hydroxyl radical scavenging, metal chelating and reducing capacities essential for growth of cells at ambient O2. At elevated O2 concentrations, a high H2O2 splitting capacity and low specific rates of H2O2 production were demonstrated in the O2-insensitive strain L. sake NCFB 2813, which could grow at elevated O2 conditions. Although H2O2 was generated in the O2-sensitive L. sake DSM 6333 at levels which were not directly toxic to the cells (<0.2 mM), we can conclude that its removal is essential for cell protection at elevated O2 conditions.