Examination of Lactobacillus plantarum lactate metabolism side effects in relation to the modulation of aeration parameters

Aims: The characterization of global aerobic metabolism of Lactobacillus plantarum LP652 under different aeration levels, in order to optimize acetate production kinetics and to suppress H2O2 toxicity. Methods and Results: Cultures of L. plantarum were grown on different aeration conditions. After sugar exhaustion and in the presence of oxygen, lactate was converted to acetate, H2O2 and carbon dioxide with concomitant ATP production. Physiological assays were performed at selected intervals in order to assess enzyme activity and vitality of the strain during lactic acid conversion. The maximal aerated condition led to fast lactate-to-acetate conversion kinetics between 8 and 12 h, but H2O2 immediately accumulated, thus affecting cell metabolism. Pyruvate oxidase activity was highly enhanced by oxygen tension and was responsible for H2O2 production after 12 h of culture, whereas lactate oxidase and NADH-dependent lactate dehydrogenase activities were not correlated to metabolite production. Limited NADH oxidase (NOX) and NADH peroxidase (NPR) activities were probably responsible for toxic H2O2 levels in over-aerated cultures. Conclusion: Modulating initial airflow led to the maximal specific activity of NOX and NPR observed after 24 h of culture, thus promoting H2O2 destruction and strain vitality at the end of the process. Significance and Impact of the study: Optimal aeration conditions were determined to minimize H2O2 concentration level during growth on lactate.