Enhanced production of glutaric acid by NADH oxidase and GabD-reinforced bioconversion from L-lysine

Abstract

Glutaric acid is a promising alternative chemical to phthalate plasticizer since it can be produced by the bioconversion of lysine. Though, recent studies have enabled the high-yield production of its precursor, 5-aminovaleric acid (AMV), glutaric acid production via the AMV pathway has been limited by the need for cofactors. Introduction of NAD(P)H oxidase (Nox) with GabTD enzyme remarkably diminished the demand for oxidized nicotinamide adenine dinucleotide (NAD(+)). Supply of oxygen through vigorous shaking had a significant effect on the conversion of AMV with a reduced requirement of NAD(+). A high conversion rate was achieved in Nox coupled GabTD reaction under optimized expression vector, terrific broth (TB), and pH 8.5 at high cell density. Supplementary expression of GabD resulted in the production of 353 +/- 35 mM glutaric acid with 88.3 +/- 8.7% conversion from 400 mM AMV. Moreover, the reaction with a higher concentration of AMV could produce 528 +/- 21 mM glutaric acid with 66.0 +/- 2.7% conversion. In addition, the co-biotransformation strategy of GabTD and DavBA whole cells could produce 282 mM glutaric acid with 70.8% conversion from lysine, compared to the 111 mM glutaric acid yield from the combined GabTD-DavBA system.