Substrate and electrode potential affect electrotrophic activity of inverted bioanodes

Abstract

Electricity-consuming microbial communities can serve as biocathodic catalysts in microbial electrochemical technologies. Initiating their functionality, however, remains a challenge. One promising approach is the polarity inversion of bioanodes. The objective of this study was to examine the impact of bioanode substrate and electrode potentials on inverted electrotrophic activity. Bioanodes derived from domestic wastewater were operated at −0.15V or +0.15V (vs. standard hydrogen electrode) with either acetate or formate as the sole carbon source. After this enrichment phase, cathodic linear sweep voltammetry and polarization revealed that formate-enriched cultures consumed almost 20 times the current (−3.0±0.78mA; −100±26A/m3) than those established with acetate (−0.16±0.09mA; −5.2±2.9A/m3). The enrichment electrode potential had an appreciable impact for formate, but not acetate, adapted cultures, with the +0.15V enrichment generating twice the cathodic current of the −0.15V enrichment. The total charge consumed during cathodic polarization was comparable to the charge released during subsequent anodic polarization for the formate-adapted cultures, suggesting that these communities accumulated charge or generated reduced products that could be rapidly oxidized. These findings imply that it may be possible to optimize electrotrophic activity through specific bioanodic enrichment procedures.