Pyruvate formation and suppression in recombinant Bacillus megaterium cultivation

A recombinant Bacillus megaterium strain showed the ability to secrete large amounts of pyruvate (up to 27.8 g l −1) for growth rates larger than 0.15 h −1. Cultivation below this growth rate avoids pyruvate formation while minimizing acetate and succinate production. Using exponential feeding, final biomass concentrations of up to 80 g l −1 were achieved. Overall molar yields for the experiments with pyruvate formation were as high as 0.79 mol mol −1. Pyruvate formation was caused by the discrepancy between glycolytic and pyruvate dehydrogenase reaction/tricarboxylic acid cycle capacities during glucose excess. High pyruvate resulted in deceleration and subsequent cessation of growth. In addition, this inhibitory effect is likely associated with the phoshoenolpyruvate:glucose phosphotransferase system used by B. megaterium as the main importer for glucose.