High level and enantioselective production of L-phenylglycine from racemic mandelic acid by engineered Escherichia coli using response surface methodology

L -Phenylglycine ( L -PHG) is a member of unnatural amino acids, and becoming more and more important as intermediate for pharmaceuticals, food additives and agrochemicals. However, the existing synthetic methods for L -PHG mainly rely on toxic cyanide chemistry and multistep processes. To provide green, safe and high enantioselective alternatives, we envisaged cascade biocatalysis for the one-pot synthesis of L -PHG from racemic mandelic acid. A engineered E. coli strain was established to co-express mandelate racemase, D -mandelate dehydrogenase and L -leucine dehydrogenase and catalyze a 3-step reaction in one pot, enantioselectively transforming racemic mandelic acid to give L -PHG ( e.e. >99 %). After the conditions for biosynthesis of L -PHG optimized by response surface methodology, the yield and space-time yield of L -PHG can reach 87.89 % and 79.70 g·L −1 ·d −1 , which was obviously improved. The high-yielding and enantioselective synthetic methods use cheap and green reagents, and E. coli whole-cell catalysts, thus providing green and useful alternative methods for manufacturing L -PHG.