We have reported increased glutamate production by a mutant of Corynebacterium glutamicum ATCC14067 (strain F172-8) with reduced H⁺-ATPase activity under biotin-limiting culture conditions (Aoki et al. Biosci. Biotechnol. Biochem., 69, 1466–1472 (2005)). In the present study, we examined valine production by an H⁺-ATPase-defective mutant of C. glutamicum. Using the double-crossover chromosome replacement technique, we constructed a newly defined H⁺-ATPase-defective mutant from ATCC13032. After transforming the new strain (A-1) with a C-terminal truncation of acetohydroxyacid synthase gene (ilvBN), valine production increased from 21.7 mM for the wild-type strain to 46.7 mM for the A-1 in shaking flask cultures with 555 mM glucose. Increased production of the valine intermediate acetoin was also observed in A-1, and was reduced by inserting acetohydroxyacid isomeroreductase gene (ilvC) into the ilvBN plasmid. After transformation with this new construct, valine production increased from 38.3 mM for the wild-type strain to 95.7 mM for A-1 strain. To the best of our knowledge, this is the first report indicating that an H⁺-ATPase-defective mutant of C. glutamicum is capable of valine production. Our combined results with glutamate and valine suggest that the H⁺-ATPase defect is also effective in the fermentative production of other practical compounds.

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