BIOCATALYST FOR PRODUCING D-LACTIC ACID

摘要

The subject of the present invention is to provide a method for producing D-lactic acid in high yield, and to provide a method for producing D-lactic acid with high selectivity, in which optical purity is high and a by-product organic acid is small. A microorganism, wherein activity of pyruvate formate-lyase (pfl-) is inactivated or decreased, and further activity of Escherichia coli-derived NADH-dependent D-lactate dehydrogenase (ldhA) is enhanced, is cultured to produce a remarkable amount of D-lactic acid in a short time. With regard to a method for enhancing ldhA activity, by linking, on a genome, a gene encoding 1dhA with a promoter of a gene which controls expression of a protein involved in a glycolytic pathway, a nucleic acid biosynthesis pathway or an amino acid biosynthesis pathway, suitable results are obtained compared to the method for enhancing expression of the gene using an expression vector. In addition, a microorganism in which a did gene is substantially inactivated or decreased is cultured to produce high quality D-lactic acid with reduced concentration of pyruvic acid. Furthermore, it is possible to suppress by-production of succinic acid and fumaric acid while maintaining high D-lactic acid productivity by using the above-mentioned microorganism having a TCA cycle, wherein activity of malate dehydrogenase (mdh) is inactivated or decreased, and further activity of aspartate ammonia-lyase (aspA) is inactivated or decreased.