Different methods used to form oxygen reducing biocathodes lead to different biomass quantities, bacterial communities, and electrochemical kinetics

Abstract

Six biocathodes catalyzing oxygen reduction were designed from the same environmental inoculum but using three different methods. Two were formed freely at open circuit potential, two using conventional aerobic polarization at -0.2V/SCE and two by reversion of already established acetate-fed bioanodes. Observation of the biofilms by SEM and epifluorescence microscopy revealed that reversible bioelectrodes had the densest biofilms. Electrochemical characterization revealed two different redox systems for oxygen reduction, at -0.30 and +0.23V/SCE. The biocathodes formed under aerobic polarization gave higher electrocalatytic performance for O reduction, due to production of the redox systems at +0.23V/SCE. Analyses of the bacterial communities on the biocathodes by 16S-rRNA pyrosequencing showed different selection (or enrichment) of microorganisms depending on the method used. This study highlights how the method chosen for designing oxygen biocathodes can affect the cathode coverage, the selection of bacterial populations and the electrochemical performance.

Electroactive Bacteria Associated With Stainless Steel Ennoblement in Seawater

“…Other electroactive bacteria have been shown to be able to change the potential of electrode under anaerobic condition (Mehanna et al, 2009), and a microbial community that was able to do the same in aerobic conditions was described as an electroactive biofilm community (Rimboud et al, 2017). This study is correlative and cannot formally establish a mechanistic link between the detected biomarker and the ennoblement, but the distinctive presence of an electrotroph bacteria in aerobic condition is, to our knowledge, a novel observation and suggest a possible metabolism for potential ennoblement.…”

“…Geobacter sulfurreducens can increase the open-circuit potential by several hundred mV on stainless steel under anoxic condition via an electrotrophic metabolism to reduce fumarate to succinate (Mehanna et al, 2009, 2010). Despite the absence of a model electrotrophic bacterium cultivated under aerobic conditions, some pure cultures were able to catalyze the electrochemical reduction of oxygen (Rabaey et al, 2008; Erable et al, 2010), as well as some environmentally enriched communities (Strycharz-Glaven et al, 2013; Rothballer et al, 2015; Milner et al, 2016; Rimboud et al, 2017). Recently, the study of a bacterial community developed on a biocathode led to the identification of “ Candidatus Tenderia electrophaga”: a strict electroautotrophic bacterium able to use a cathode as an electron donor to reduce oxygen and able to fix carbon dioxide (Eddie et al, 2016).…”

Catalysis of the electrochemical oxygen reduction reaction (ORR) by animal and human cells

“…In this framework, ORR is most often achieved by multispecies microbial biofilms formed directly in natural media (seawater [4,[8][9][10][11], wastewater [12], etc. ), or in synthetic media inoculated with natural multi-species inocula [13][14][15][16][17][18][19]. Considerable current densities, of the order of an A/m 2 , and high half-wave potentials, above 0.4 V/ SHE, have been reached [14,15,17,19].…”

Effect of Electrode Properties on the Performance of a Photosynthetic Microbial Fuel Cell for Atrazine Detection

“…The response time of the p-MFCs to atrazine was in the range of hours, instead of minutes as reported for other algae biosensors (Shitanda et al, 2005;Tahirbegi et al, 2016). Mass transfer limitations, especially within the porous structure of the GF cathode, and low electrode surface-area-to-volume-ratio, may be a reason for this (Rimboud et al, 2017).…”