Synthesis of Phenyllactic acid by Metabolically Engineered Escherichia coli with in situ generation of NADH

Phenyllactic acid (PLA) is known as an ideal antimicrobial compound with broad and effective antimicrobial activity against both bacteria and fungi. PLA is naturally produced by some classed of microorganisms, especially lactic acid bacteria (LAB). The synthesis of PLA in LAB results from the catabolism of phenylalanine, in which phenylalanine is transaminated to phenylpyruvic acid (PPA) and PPA further reduced to PLA. A recombinant Escherichia coli harboring an additional transaminase and a mutant NAD-dependent D-lactate dehydrogenase dehydrogenase from Lactobacillus bulgaricus, which was responsible for PPA reduction activity was constructed. In addition, we introduced a NADH regeneration system in the coupled reaction pathway. Based on 50 mM of L-phenylalanine used, about 40% final product conversion yield of D-Phenyllactic acid was achieved by biotransformation of the recombinant E. coli.