Applied Microbiology and Biotechnology, Vol.79, No.3, 471-479, 2008
Corynebacterium glutamicum tailored for high-yield L-valine production
We recently engineered the wild type of Corynebacterium glutamicum for the growth-decoupled production of L-valine from glucose by inactivation of the pyruvate dehydrogenase complex and additional overexpression of the ilvBNCE genes, encoding the L-valine biosynthetic enzymes acetohydroxyacid synthase, isomeroreductase, and transaminase B. Based on the first generation of pyruvate-dehydrogenase-complex-deficient C. glutamicum strains, a second generation of high-yield L-valine producers was constructed by successive deletion of the genes encoding pyruvate:quinone oxidoreductase, phosphoglucose isomerase, and pyruvate carboxylase and overexpression of ilvBNCE. In fed-batch fermentations at high cell densities, the newly constructed strains produced up to 410 mM (48 g/l) L-valine, showed a maximum yield of 0.75 to 0.86 mol/mol (0.49 to 0.56 g/g) of glucose in the production phase and, in contrast to the first generation strains, excreted neither pyruvate nor any other by-product tested.
Keywords:Corynebacterium glutamicum;L-valine production;pyruvate dehydrogenase complex;pyruvate : quinone oxidoreductase;phosphoglucose isomerase;pyruvate carboxylase