Analysis of the contribution of different electron transfer pathways for hydrogen production in a bioelectrochemically assisted dark fermentation system

Abstract

This research analyzed the contribution of different electron transfer pathways for H2 production in a bioelectrochemicallly assisted dark fermentation system (BEDF), and compared to an electric field-driven dark fermentation (EFDF) reactor. The results showed that intrinsic extracellular electron transfer (iEET) via dark fermentation accounted for 76.3% of the H2 production in the BEDF reactor. In comparison, the extracellular electron transfer (bEET) pathway via the bioelectrode enhanced by the bioelectrochemical system and the electric field-driven extracellular electron transfer (eEET) in the bulk solution accounted for 5% and 18.7%, respectively. This suggests that the main electron transfer pathway for H2 production comes from the bulk solution rather than that on the bioelectrodes. Under the condition of electric field, extracellular polymeric substances (EPS) were secreted in large quantities in the bulk solution, and electroactive microorganisms such as Proteobacteria were significantly enriched, which further promote the H2 production through the eEET pathway.