Overexpression of ydbK-encoding putative pyruvate synthase improves L-valine production and aerobic growth on ethanol media by an Escherichia coli strain carrying an oxygen-resistant alcohol dehydrogenase

Abstract

Based on homology with anaerobic enzymes, E. coli YdbK was annotated as a putative pyruvate: ferredoxin/ flavodoxin-oxidoreductase (PFOR) / pyruvate synthase. Expression of ydbK was shown in wild-type E. coli because inactivation of the gene made the cells incapable of growing on glucose under oxidative stress caused by the addition of methyl viologen (MV). Cell growth was restored by the introduction of an ydbK-carrier plasmid. We proposed that pyruvate synthase (PYRS)-catalyzed pyruvate formation could stimulate ethanol consumption and enhance pyruvateoriginated biosynthesis. Indeed, the most efficient growth on ethanol and production of L-valine were detected for the ydbK-overexpressing variant among the tested E. coli strains generating oxygen-resistant alcohol dehydrogenase, a product of the mutant adhE gene, with a constitutively expressed L-valine biosynthetic operon, ilvGMED. Therefore, E. coli YdbK could be involved in oxidative stress protection via PFOR activity and function as a PYRS during aerobic growth on ethanol. © 2010 Eremina NS, et al.