Regulation of the NADH supply by nuoE deletion and pncB overexpression to enhance hydrogen production in Enterobacter aerogenes

In this study, seven mutants from E. aerogenes IAM1183 wildtype were constructed via different strategies including deletion of lactate dehydrogenase, disruption of NADH dehydrogenase gene nuoE, overexpression of pncB and a combination of both to regulate of the NADH supply to enhance hydrogen production. Compared with the parental strain, the hydrogen yields of the strains IAM1183-E, IAM1183-L and IAM1183-EL increased by 23.3, 81.7 and 97.9%, respectively. When the pncB gene was overexpressed, the hydrogen yield of IAM1183/P, IAM1183-E/P, IAM1183-L/P and IAM1183-EL/P increased by 39.0, 6.5, 5.9, and 5.1% compared with the respective original knockout strains. Among them, the total hydrogen yield of strain IAM1183-EL/P with highest production efficiency was 58% higher than IAM1183. Further metabolite analysis indicated that the knockout of nuoE and ldhA, combined with the overexpression of pncB, resulted in a redistribution of the metabolic fluxes in E. aerogenes, which led to an improvement of the hydrogen yield.