Efficient Production of Phenyllactic Acid by Whole-cell Biocatalysis with Cofactor Regeneration System
D-phenyllactic acid is a value added chemical with potential uses in wide areas of industry such as antibiotics, biopolymers, and pharmaceutical syntheses. It can be reduced from phenylpyruvic acid by various 2-hydroxy acid dehydrogenases. In this work, the 2-hydroxy acid dehydrogenase from Oenococcus oeni has been expressed in Escherichia coli whole cell along with formate dehydrogenases from two difference sources, Candida boidinii and Pseudomonas species, for regeneration of NADH cofactor. This could enhance the conversion of the product up to 78%, 3.4-fold increase from the one without cofactor regeneration, demonstrating a possibility of an efficient D-phenyllactic acid production system. Structural analysis by molecular dynamics
simulation indicated the flexibility of the enzyme was lowered when the bound substrate was phenylpyruvic acid, compared to the natural substrate, pyruvate. This can be exploited to design 2-hydroxy acid dehydrogenase to increase the flexibility for phenylpyruvic acid, in order to further improve the production of D-phenyllactic acid.