Microbial activity influences electrical conductivity of biofilm anode

This study assessed the conductivity of a Geobacter-enriched biofilm anode in a microbial electrochemical cell (MxC) equipped with two gold anodes (25 mM acetate medium), as different proton gradients were built throughout the biofilm. There was no pH gradient across the biofilm anode at 100 mM phosphate buffer (current density 2.38 A/m²) and biofilm conductivity (K_bio) was as high as 0.87 mS/cm. In comparison, an inner biofilm became acidic at 2.5 mM phosphate buffer in which dead cells were accumulated at ∼80 microm of the inner biofilm anode. At this low phosphate buffer, K_bio significantly decreased by 0.27 mS/cm, together with declined current density of 0.64 A/m². This work demonstrates that biofilm conductivity depends on the composition of live and dead cells in the conductive biofilm anode.