Reversible Effects of Periodic Polarization on Anodic Electroactive Biofilms

Anodic electroactive biofilms (EABs) are commonly grown under continuous polarization of the underlying electrode. Their growth under appropriate periodic polarization was recently reported to considerably enhance their electrochemical properties (catalytic current and charge carriers concentration). This improvement was only investigated on relatively short term (ten days), and its resilience once the periodic polarizations are switched back to continuous (or vice versa) has not yet been assessed. Here, we first cultivated 16 Geobacter-dominated EABs on glassy carbon electrodes under either continuous or periodic polarization for several days. The polarization mode was then switched from continuous to periodic and vice versa. The improvement induced by the initial periodic polarization was lost over only two days of continuous polarization. Conversely, it took about ten days of periodic polarization to fully improve the electroactivity of the EABs initially grown under continuous polarization. The periodic polarization favored biofilm detachments, which were followed by a full recovery of current within three days. The performance of EABs under periodic polarization was less negatively impacted under substrate-limiting conditions, likely because of substrate replenishment during open circuit periods.