High Biofilm Conductivity Maintained Despite Anode Potential Changes in a Geobacter-Enriched Biofilm

This study systematically assessed intracellular electron transfer (IET) and extracellular electron transfer (EET) kinetics with respect to anode potential (E_anode) in a mixed-culture biofilm anode enriched with Geobacter spp. High biofilm conductivity (0.96–1.24 mS cm⁻¹) was maintained during E_anode changes from −0.2 to +0.2 V versus the standard hydrogen electrode (SHE), although the steady-state current density significantly decreased from 2.05 to 0.35 A m⁻² in a microbial electrochemical cell. Substantial increase of the Treponema population was observed in the biofilm anode at E_anode=+0.2 V, which reduced intracellular electron-transfer kinetics associated with the maximum specific substrate-utilization rate by a factor of ten. This result suggests that fast EET kinetics can be maintained under dynamic E_anode conditions in a highly conductive biofilm anode as a result of shift of main EET players in the biofilm anode, although E_anode changes can influence IET kinetics.