Hydrogen peroxide production by Zymomonas mobilis

Summary The anaerobic aerotolerant bacterium Zymomonas mobilis 113 produced superoxide (O₂^-) and hydrogen peroxide (H₂O₂) under aerobic conditions. The main generators of H₂O₂ were glucose oxidase and superoxide dismutase (SOD). The O₂^-generation was probably related to minor alternative reduced nicotinamide adenine zinucleotide (NADH)-oxidation reactions in the electron transport chain. An increase in medium pO₂ was observed during growth of Z. mobilis 113 in a batch culture. The maximum pO₂ increase correlated with glucose oxidase and SOD activities. An decrease in medium pO₂ value coincided with an increase in catalase activity in batch culture. Medium deoxygenation reduced the pO₂ effect, yet the culture still responded with a pO₂ increase after inoculation and addition of the feeding medium. We conclude that the apparent pO₂ effects are related to changes in H₂O₂ concentration in the culture liquid.