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

This research analyzed the contribution of different electron transfer pathways for H 2 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 H 2 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 H 2 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 H 2 production through the eEET pathway. [Display omitted] • H 2 production was increased by electric field rather than that on bioelectrode. • BEET and eEET pathways account for 5% and 18.7% of total hydrogen production. • Electric fields activate more hydrogen-producing microbial metabolic pathways. • Electric field enriches bacteria that affect EPS secretion in bulk solution. [ABSTRACT FROM AUTHOR]