초록
A novel NAD<SUP>+</SUP>-dependent D-mandelate dehydrogenase was identified from Lactobacillus brevis (LbDMDH). After purified to homogeneity, the optimum pH and temperature for oxidation of D-mandelate were pH 10.0 and 40<SUP>o</SUP>C, and the K<SUB>m</SUB> and k<SUB>cat</SUB> were 1.1mM and 355s<SUP>-1</SUP> respectively. Employing the LbDMDH together with a mandelate racemase from Pseudomonas putida and a leucine dehydrogenase (EsLeuDH) from Exiguobacterium sibiricum, we established a three-step one-pot domino reaction system for preparing chiral L-phenylglycine from racemic mandelic acid with internal cofactor recycling. Under the optimum conditions, 30.4g rac-mandelic acid (0.2M) at 1L scale had been converted into chiral L-phenylglycine, with 96.4% conversion, 86.5% isolation yield, >99% ee<SUB>p</SUB> and 50.4gL<SUP>-1</SUP>d<SUP>-1</SUP> space-time yield.