In mineral salts medium under oxygen deprivation, Corynebacterium glutamicum exhibits high productivity of L: -lactic acid accompanied with succinic and acetic acids. In taking advantage of this elevated productivity, C. glutamicum was genetically modified to produce D: -lactic acid. The modification involved expression of fermentative D: -lactate dehydrogenase (D: -LDH)-encoding genes from Escherichia coli and Lactobacillus delbrueckii in L: -lactate dehydrogenase (L: -LDH)-encoding ldhA-null C. glutamicum mutants to yield strains C. glutamicum DeltaldhA/pCRB201 and C. glutamicum DeltaldhA/pCRB204, respectively. The productivity of C. glutamicum DeltaldhA/pCRB204 was fivefold higher than that of C. glutamicum DeltaldhA/pCRB201. By using C. glutamicum DeltaldhA/pCRB204 cells packed to a high density in mineral salts medium, up to 1,336 mM (120 g l(-1)) of D: -lactic acid of greater than 99.9% optical purity was produced within 30 h.