Insights into microbial metabolic coordination under driving force of different conductive materials-mediated direct interspecies electron transfer during anaerobic digestion.

[Display omitted] • AD patterns in different CMs-mediated AD systems were evaluated at high pH 2. • Abundant electron-exchanging functional groups in biochar promoted maximum DIET flux. • DIET interaction types between acetate oxidizers and Methanothrix relied on added CMs. • CMs selectively induced metabolic coordination from aspect of energy/electron flux. • Functional characteristics of different CMs-mediated DIET optimized CMs selection. In this study, different carbon/metal-based conductive materials (CMs) were amended in traditional anaerobic digestion (AD) system with high hydrogen partial pressure (pH 2) to verify the operational feasibility of CMs-mediated direct interspecies electron transfer (DIET). Operational performances revealed that SCOD removal efficiencies and CH 4 production of CMs-mediated groups including GS (graphene), CTS (carbon nanotube), BS (biochar), IS (magnetite) and MS (MnO 2) were increased by 34.7 %-157.3 %, 33.0 %-154.4 %, 41.2–169.6 %, 30.7 %-146.7 % and 28.1 %-139.5 % when compared with those of control group (54.5 ± 4.1 % and 184.9 ± 12.5 mL/g·VSS). Additionally, electron transfer capacity measurement showed that the equivalent current of biochar-mediated DIET flux (7 × 10-3 A) was 102 and 109 times higher than those in magnetite-mediated and interspecies H 2 transfer (IHT) conditions due to presence of abundant electron-exchanging functional groups. Furthermore, dynamic microbiome distribution and anaerobic metabolism analysis proved that genes encoding syntrophic enzymes were highly stimulated in GS, CTS and BS while genes encoding acidogenic enzymes were more expressed in IS and MS with acetate oxidizers and Methanothrix as CMs-mediated DIET participants, suggesting that metabolic coordination of fermentative bacteria could be selectively induced to cooperate with DIETers for maintaining stable operation of each CMs-mediated AD systems in high pH 2 condition. Overall, this study could offer better understand on application strategies of carbon-based and metal-based CMs for inducing the distinct CMs-mediated DIET process, which further optimized selection basis of CMs and widened real application of CMs-mediated DIET. [ABSTRACT FROM AUTHOR]