Unraveling the roles of lanthanum-iron oxide nanoparticles in biohydrogen production.

Low hydrogen (H) yield via dark fermentation often occurs, being mainly due to H generation pathway shift. In this study, lanthanum-iron oxide nanoparticles (LaFeO NPs) were prepared to investigate their effects on bioH production. The highest H yield of 289.8 mL/g glucose was found at 100 mg/L of LaFeO, being 47.6% higher than that from the control (196.3 mL/g glucose). The relative abundance of Firmicutes increased from 54.2% to 67.5%. The large specific surface area of LaFeO provided sufficient sites for the colonization of Firmicutes and increased the bacterial access to nutrients. Additionally, the La gradually released from LaFeO NPs raised microbial transmembrane transport capacity, promoting glycolytic efficiency and Fe availability, thereby increasing hydrogenase content, and shifting the bioH evolution to butyrate pathway for more H. This provides the novelty for biochemical utilization of La and new insights into the improved H yield amended with LaFeO.