Efficient production and secretion of pyruvate from Halomonas sp. KM-1 under aerobic conditions

The alkaliphilic, halophilic bacterium Halomonas sp. KM-1 can utilize both hexose and pentose sugars for the intracellular storage of bioplastic poly-(R)-3-hydroxybutyric acid (PHB) under aerobic conditions. In this study, we investigated the effects of the sodium nitrate concentration on PHB accumulation in the KM-1 strain. Unexpectedly, we observed the secretion of pyruvate, a central intermediate in carbon- and energy-metabolism processes in all organisms; therefore, pyruvate is widely used as a starting material in the industrial biosynthesis of pharmaceuticals and is employed for the production of crop-protection agents, polymers, cosmetics, and food additives. We then further analyzed pyruvate productivity following changes in culture temperature and the buffer concentration. In 48-h batch-cultivation experiments, we found that wild-type Halomonas sp. KM-1 secreted 63.3 g/L pyruvate at a rate of 1.32 g/(L·h), comparable to the results of former studies using mutant and recombinant microorganisms. Thus, these data provided important insights into the production of pyruvate using this novel strain.