Enhanced biohydrogen production from cotton stalk hydrolysate of Enterobacter cloacae WL1318 by overexpression of the formate hydrogen lyase activator gene

Biohydrogen production from lignocellulose has become an important hydrogen production method due to its diversity, renewability, and cheapness. Overexpression of the formate hydrogen lyase activator ( ) gene is a promising tactic for enhancement of hydrogen production in facultative anaerobic . As a species of , was reported as a highly efficient hydrogen-producing bacterium. However, little work has been reported in terms of cloning and expressing the gene in for lignocellulose-based hydrogen production. In this study, the formate hydrogen lyase activator ( ) gene was cloned and overexpressed in WL1318. We found that the recombinant strain significantly enhanced cumulative hydrogen production by 188% following fermentation of cotton stalk hydrolysate for 24 h, and maintained improved production above 30% throughout the fermentation process compared to the wild strain. Accordingly, overexpression of the gene resulted in an enhanced hydrogen production potential ( ) and maximum hydrogen production rate ( ), as well as a shortened lag phase time ( ) for the recombinant strain. Additionally, the recombinant strain also displayed improved glucose (12%) and xylose (3.4%) consumption and hydrogen yield Y(H /S) (37.0%) compared to the wild strain. Moreover, the metabolites and specific enzyme profiles demonstrated that reduced flux in the competitive branch, including succinic, acetic, and lactic acids, and ethanol generation, coupled with increased flux in the pyruvate node and formate splitting branch, benefited hydrogen synthesis. The results conclusively prove that overexpression of gene in WL1318 can effectively enhance the hydrogen production from cotton stalk hydrolysate, and reduce the metabolic flux in the competitive branch. It is the first attempt to engineer the gene in the hydrogen-producing bacterium . This work provides a highly efficient engineered bacterium for biohydrogen production from fermentation of lignocellulosic hydrolysate in the future.