The positive effects
of metal oxide nanoparticles (NPs)
on dark
fermentation (DF) for biohydrogen synthesis have been increased, and
the mechanism still needs to be further revealed. In this study, nickel–cobalt
oxide (NiCo2O4) NPs were prepared to increase
H2 yield via DF. The highest (259.67 mL/g glucose) and
the lowest (188.14 mL/g glucose) yields were achieved at 400 and 800
mg/L NiCo2O4 NPs added, respectively, with their
corresponding 33.97% increase and 2.93% decrease compared with the
control yield (193.82 mL/g glucose). Meanwhile, the microbial community
further confirmed that NiCo2O4 NPs increased
the abundance of the dominant H2-producing Clostridium sensu stricto
1 by 23.05%.
The gene prediction also showed that NiCo2O4 NPs increased the abundance of genes encoding the rate-limiting
enzyme pyruvate kinase in glycolysis, thus increasing the substrate
conversion. Moreover, the gene abundance of key enzymes directly related
to H2 evolution was also increased at different levels.