Alteration of anaerobic metabolism in Escherichia coli for enhanced hydrogen production by heterologous expression of hydrogenase genes originating from Synechocystis sp

Abstract

Metabolic engineering is recognized as one of the most important technologies for improving fermentative hydrogen yield. A vector with hydrogenase genes ( hoxEFUYH) from Synechocystis sp. PCC 6803 under an alkB promoter was constructed, and introduced into Escherichia coli DH5α to alter the hydrogen metabolism with glucose as the sole carbon source. The recombinant strain reached a highest hydrogen yield of 1.89 mol/mol glucose, which was 95% of the theoretical hydrogen yield of E. coli. Hydrogenase activities for hydrogen evolution were increased and formic acid assimilation was accelerated with the expression of hoxEFUYH. The expression of hoxEFUYH suppressed the transcription of native hydrogenase 1 and hydrogenase 2, which were responsible for hydrogen uptake activity, while it had no influence on the transcription of the hydrogenase 3. Moreover, as the electron donor of HoxEFUYH is NADH, the expressed HoxEFUYH expanded the substrate specificity of the hydrogen-evolving hydrogenase in E. coli.