Synergistic improvement of biohydrogen yield from food wastewater using Clostridium puniceum and magnetite-biochar.

Biohydrogen production using waste resources and microorganisms was gaining attention as a clean energy alternative that could reduce production cost and environmental pollution. Among waste resources, food wastewater (FW) was especially suitable due to its high lactate content, which supported microbial hydrogen production. However, FW also contained inhibitory compounds that could limit microbial activity. Considering biochar was known to adsorb heavy metals and emerging pollutants and magnetite was known to promote electron flow between microbial cells and the extracellular environment, our approach combined magnetite biochar (MBC) to improve hydrogen production from anaerobic strain by finding suitable match of Clostridium. To realize this, seven Clostridium was examined to find the optimal strain, and as a result, Clostridium puniceum showed the most significant synergistic effect with lactate and MBC. Under optimized conditions, the addition of MBC increased lactate consumption by 2.1 times compared to the control without MBC and hydrogen production was improved by 37.6% within 12 h. Furthermore, the MBC retained its functional capacity for at least 6 cycles of reuse. Finally, the same conditions were applied to actual FW resulting in comparable result with pure lactate, showing the practical application and the robustness of system. Since C. puniceum has not been widely studied as a single strain for hydrogen production, but this study highlighted its strong potential of C. puniceum when it was used with MBC. Its stable performance and synergy with MBC suggested broader applicability in sustainable biohydrogen production using waste-derived substrates.