Impact of carrier capacitance on Geobacter enrichment and direct interspecies electron transfer under anaerobic conditions

Direct interspecies electron transfer (DIET) enhances anaerobic digestion by facilitating electron exchange between electroactive bacteria and methanogenic archaea. While Geobacter species are recognized for donating electrons to methanogens via DIET, they are rarely detected in mixed microbial communities. This study examined various non-electrode biological carriers (zeolite, carbon cloth, activated carbon and biochar) to promote Geobacter cultivation under anaerobic conditions and identify pivotal factors influencing their symbiosis with methanogens. Capacitive materials, such as activated carbon and biochar, significantly enriched Geobacter populations and strengthened DIET-based mutualism with Methanosarcina, both in the presence and absence of electric fields. Partial least-squares path modeling revealed that the porous structure and functional groups of materials positively and directly influenced the abundance of Geobacter and Methanosarcina. These findings contribute to a deeper understanding of critical properties of capacitive materials for screening functional microorganisms and guiding the design of electroactive materials to augment anaerobic treatment processes.