Improving hydrogen production via electro-fermentation: Insights of gas and soluble metabolites production

Dark fermentation is an effective means to convert organic waste to hydrogen for bioenergy utilization but is limited by non-hydrogen-producing pathways. Emerging electro-fermentation technology promises to improve it by modulating dominant metabolic pathways. This study investigated the impact of electro-fermentation performance with voltages and substrate concentrations. The results revealed that the specific hydrogen yields at 0.3–0.6 V voltage were increased by 31.5%–91.3% over the control, and substrate degradation efficiency were also improved by 13.3%–20.7%. When the voltage was applied, the abundance of the hydrogen-producing bacteria Clostridium species increased 2.6–8.1 times more than the conventional. Meanwhile, an increase of 74.6%–311.5% in electron transfer system activity was quantified with nearly doubling the thickness of the biofilm. High soluble metabolite acetate/butyrate expression provided evidence that electro-fermentation promotes both favorable hydrogen production pathways. This study provides new insights into the application of electro-fermentation as a strategy for improving sustainable hydrogen production.