초록
The d-lactic acid producing strain, Escherichia coli HBUT-D, was reengineered for l(+)-lactic acid fermentation by replacing the d-lactate dehydrogenase gene (ldhA) with an l(+)-lactate dehydrogenase gene (ldhL) from Pedicoccus acidilactici, followed by adaptive evolution in sucrose. The resulting strain, WYZ-L, has enhanced expression of the sucrose operon (cscA and cscKB). In 100gL<SUP>-1</SUP> of sucrose fermentation using mineral salt medium, WYZ-L produced 97gL<SUP>-1</SUP> of l(+)-lactic acid, with a yield of 90%, a maximum productivity of 3.17gL<SUP>-1</SUP>h<SUP>-1</SUP> and an optical purity of greater than 99%. In fermentations using sugarcane molasses and corn steep liquor without additional nutrients, WYZ-L produced 75gL<SUP>-1</SUP> of l(+)-lactic acid, with a yield of 85%, a maximum productivity of 1.18gL<SUP>-1</SUP>h<SUP>-1</SUP>, and greater than 99% optical purity. These results demonstrated that WYZ-L has the potential to use waste molasses and corn steep liquor as a resource for l(+)-lactic acid fermentation.