Genome-resolved insights into Ni/Fe₂O₃ nanocatalyst-enhanced dark fermentative hydrogen production from food waste

Ni/Fe2O3 nanocatalysts are effective in increasing the yield of fermentative biohydrogen (H2); however, the underlying microbial and metabolic mechanisms remain insufficiently understood. In this study, food waste (FW)-based dark fermentative (DF) H2 production was significantly improved by the addition of a synthesized Ni/Fe2O3 nanocatalyst, achieving an increase in H2 yield up to 55.65% compared with that in the control. The presence of Ni/Fe2O3 enhanced the pH stability, conductivity, and electron transport capacity of the system, thereby simultaneously accelerating the microbial metabolism in the DF system. Genome-centric metagenomic analysis revealed that the catalyst reshaped the microbial community and metabolic functions by promoting Clostridium species as the dominant H2-producing bacteria and enriching the genes associated with carbohydrate metabolism, complex saccharide hydrolysis, nutrient transport, glucose phosphorylation, and electron transfer pathways. These findings uncover a previously unrecognized catalytic role of Ni/Fe2O3 in regulating the microbial community structure and metabolic pathways, providing genome-level insights into catalyst–microbe interactions and offering a mechanistic foundation for advancing food waste-derived H2 production.