[Enzymes related with NAD synthesis promote conversion of 1,4-butanediol to 4-hydroxybutyrate].

Besides medical application, 4-hydroxybutyrate (4-HB) is a precursor of P3HB4HB, a bioplastic showing excellent physical properties and degradability. Escherichia coli S17-1 (pZL-dhaT-aldD) can transform 1, 4-butanediol (1,4-BD) into 4HB with participation of cofactor NAD. To enhance productivity, nicotinic acid phosphoribosyltransferase (PncB) and nicotinamide adenine dinucleotide synthetase (NadE) were overexpressed to increase intracellular nicotinamide adenine dinucleotide concentration and promote reaction process. The shake flask fermentation result showed that the conversion rate increased by 13.03% with help of PncB-NadE, leading to 4.87 g/L 4HB from 10 g/L 1,4-BD, and productivity was increased by 40.91% to 1.86 g/g. These results demonstrated that expression of PncB and NadE is beneficial for conversion of 1,4-BD to 4HB.