Mechanism of ZnFe2O4 NPs on biohydrogen production by Clostridium pasteurianum

Abstract

The biohydrogen production in Dark fermentation (DF) could be enhanced by ZnFe2O4 nanomaterials (NPs). The optimum conditions were obtained by a response surface method. Eventually, a biohydrogen production of 2645 mL/L was obtained after 48 h of batch culture, which is 116% higher than control without ZnFe2O4 NPs. The mechanism was investigated by a multi-scale method. In bioreactor scale, ZnFe2O4 NPs could enhance the glucose metabolic ability of C. pasteurianum to promote cell growth and biohydrogen production. The metabolic pathways of biohydrogen production were shifted from the butyric acid-type to the ethanol-type. In cellular scale, ZnFe2O4 NPs could reduce bacterial flagella assembly. In macromolecule scale, the activities of hydrogenase and ethanol dehydrogenase were increased. In genetic scale, the differentially expressed genes mainly involved in biohydrogen production, like those encoded Fe-only hydrogenase, ethanol dehydrogenase, and nitrogenase were up-regulated. The results could provide theoretical and technical supports for the development of commercial biohydrogen process.