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.