초록
<P>A Corynebacterium glutamicum strain with inactivated pyruvate dehydrogenase complex and a deletion of the gene encoding the pyruvate:quinone oxidoreductase produces about 19?mM L: -valine, 28?mM L: -alanine and about 55?mM pyruvate from 150?mM glucose. Based on this double mutant C. glutamicum aceE pqo, we engineered C. glutamicum for efficient production of pyruvate from glucose by additional deletion of the ldhA gene encoding NAD(+)-dependent L: -lactate dehydrogenase (LdhA) and introduction of a attenuated variant of the acetohydroxyacid synthase (C-T IlvN). The latter modification abolished overflow metabolism towards L: -valine and shifted the product spectrum to pyruvate production. In shake flasks, the resulting strain C. glutamicum aceE pqo ldhA C-T ilvN produced about 190?mM pyruvate with a Y (P/S) of 1.36?mol per mol of glucose; however, it still secreted significant amounts of L: -alanine. Additional deletion of genes encoding the transaminases AlaT and AvtA reduced L: -alanine formation by about 50%. In fed-batch fermentations at high cell densities with adjusted oxygen supply during growth and production (0-5% dissolved oxygen), the newly constructed strain C. glutamicum aceE pqo ldhA C-T ilvN alaT avtA produced more than 500?mM pyruvate with a maximum yield of 0.97?mol per mole of glucose and a productivity of 0.92?mmol?g ((CDW)) (-1) ?h(-1) (i.e., 0.08?g?g((CDW)) (-1)?h(-1)) in the production phase.</P>