Efficient production of (R)-2-hydroxy-4-phenylbutyric acid by using a coupled reconstructed D-lactate dehydrogenase and formate dehydrogenase system.

BACKGROUND: (R)-2-hydroxy-4-phenylbutyric acid [(R)-HPBA] is a key precursor for the production of angiotensin-converting enzyme inhibitors. However, the product yield and concentration of reported (R)-HPBA synthetic processes remain unsatisfactory.

METHODOLOGY/PRINCIPAL FINDINGS: The Y52L/F299Y mutant of NAD-dependent D-lactate dehydrogenase (D-nLDH) in Lactobacillus bulgaricus ATCC 11842 was found to have high bio-reduction activity toward 2-oxo-4-phenylbutyric acid (OPBA). The mutant D-nLDHY52L/F299Y was then coexpressed with formate dehydrogenase in Escherichia coli BL21 (DE3) to construct a novel biocatalyst E. coli DF. Thus, a novel bio-reduction process utilizing whole cells of E. coli DF as the biocatalyst and formate as the co-substrate for cofactor regeneration was developed for the production of (R)-HPBA from OPBA. The biocatalysis conditions were then optimized.

CONCLUSIONS/SIGNIFICANCE: Under the optimum conditions, 73.4 mM OPBA was reduced to 71.8 mM (R)-HPBA in 90 min. Given its high product enantiomeric excess (>99%) and productivity (47.9 mM h(-1)), the constructed coupling biocatalysis system is a promising alternative for (R)-HPBA production.