Effects of NADH Availability on 3-Phenyllactic Acid Production by Lactobacillus plantarum Expressing Formate Dehydrogenase.

It is well known that cofactors play a key role in the production of different compounds in bioconversion processes, while the high cost of cofactors limits their usage in industrial applications. In the present study, a NADH regeneration system was successfully developed in Lactobacillus plantarum by expressing the fdh gene coding for formate dehydrogenase (FDH) from Candida boidinii. Results indicated that the FDH was expressed with the highest activity of 0.82 U/mg of protein when cells entered early stationary phase. In addition, the expression of FDH increased the intracellular level of NADH and NADH/NAD ratio in L. plantarum, and therefore, enhanced the NADH-dependent production of 3-phenyllactic acid (PLA) in repeated and fed-batch bioconversions. In brief, the results demonstrate that the NADH regeneration by expressing FDH is a promising strategy for producing NADH-dependent microbial metabolites in L. plantarum.