Unlocking the Potential of Ni/Fe2O3 Bimetallic Nanoparticles for Fermentative Biohydrogen Production

The coordinated system of inorganic nanoparticle-intact living cells has shown great potential in fermentative hydrogen (H₂) production. Meanwhile, sluggish electron transfer and energy loss during transmembrane diffusion restrict the production of biohydrogen (BioH₂). Herein, iron oxide, nickel oxide, and Ni/Fe₂O₃ bimetallic nanocomposites were prepared through the coprecipitation method to investigate their potential effect on the dark fermentative hydrogen production (DFHP) system. The results showed that BioH₂ production could be enhanced by using nickel and iron oxide composites in DFHP, surpassing the performance of individual iron oxide or nickel oxide and their physical mixture. Specifically, Ni/Fe₂O₃-5% added to the feed at 150 mg/L increased the BioH₂ yields by 51.24% compared to that in its controlled experiment. The microbial community analysis confirmed a significant change in compositional proportions of the microbiome structure of DFHP in response to Ni/Fe₂O₃-5 wt %. The Enterobacter species proportions increased from 32.0% to 39.0%, along with some unclassified genera of microbial communities, from 34.0% to 42.0%, by supplementation of the nanomaterials. Enterobacter species are versatile facultative hydrogen producers and can use various organic wastes as the sole carbon source. The results suggested that the supplemented Ni/Fe₂O₃-5% induced the glycolytic efficacy and Fe and Ni availability, thereby increasing the hydrogenase activities. This study provided novel insights into integrating Ni/Fe₂O₃ into the DFHP system and depicted its potential as an excellent catalyst to increase BioH₂ production. The distinctive microbial communities, unidentified hydrogen-producing bacteria, and increased BioH₂ yield due to the presence of Ni/Fe₂O₃ in the DFHP system suggest unique and substantial advantages for the sustainable use of bimetallic nanomaterials in fermentation technology.