[Effects of cultivation conditions on the optical purity of L(+)-lactic acid].

The effect of cultivation conditions on the optical purity of L(+)-lactic acid produced by Rhizopus oryzae HZS6 was investigated. The isomeric composition of lactic acid was influenced by the supplementation of L(+)-lactic acid to fermentation medium. L(+)-isomer increased with the dosage, no D(-)-lactic acid was observed when the concentration of supplemented L(+)-lactic acid in matrix was > or = 1.5 g/L. However, the L(+)-lactic acid yield, biomass and glucose conversion rate decreased with the dosage. With the same method, the supplementation of L(+)-lactic to substrate had no influence on isomeric composition of lactic acid by Lactobacillus and Escherichia coli.