Reversible Effects of Periodic Polarization on Anodic Electroactive Biofilms

Abstract

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.

Availability of Hydrogen Shapes the Microbial Abundance in Biofilm Anodes based onGeobacterEnrichment

“…Albeit CE and of 1‐CR (149.3±16.3 % and 0.57±0.07 mA cm −2 ) are considerably higher than of 2‐CR (30.2±18.2 % and 0.33±0.14 mA cm −2 ) and 2‐CR+H 2 (49.7±5.2 % and 0.38±0.03 mA cm −2 ) in the 1 st batch cycle, both parameters converge in the following batch cycles to comparable values (Figure b–c). The observed resemble values typically found in literature for Geobacter enrichment biofilms cultivated in 1‐CR and 2‐CR . The derived average CE of 2‐CR (39.7±14.3 %) and 2‐CR+H 2 (48.7±7.7 %) are low compared to the majority of literature.…”

Redox Potential Heterogeneity in Fixed‐Bed Electrodes Leads to Microbial Stratification and Inhomogeneous Performance

“…Although fixed bedBES represent a putative redox stratified environment, [9] their microbial ecology is sparsely investigated. In contrast, EAM and related microbiomes at monolithic electrodes are well studied [28,29] . The redox potential is a key variable to shape microbial composition and microbial physiology including thermodynamics and kinetics of EAM [30–36] .…”

Electron Storage in Electroactive Biofilms

“…The EAB in this study was dominated by Geobacter species. Another study by the same group showed that these changes in morphology were only visible when the growing EABs were continuously exposed to these intermittent conditions and for a term longer than 10 days [21]. Regarding electroactive species growing on the anode, no significant effect on the presence of Geobacter was observed.…”

“…In recent years, the interest in the behavior of EABs during intermittent operation has increased [18][19][20][21][22][23]. Kubannek and coworkers measured the CO 2 production as a measure of metabolic activity [24].…”