Protons accumulation during anodic phase turned to advantage for oxygen reduction during cathodic phase in reversible bioelectrodes

Abstract

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 13877 b s t r a c tReversible bioelectrodes were designed by alternating acetate and oxygen supply. It was demonstrated that the protons produced and accumulated inside the biofilm during the anodic phase greatly favored the oxygen reduction reaction when the electrode was switched to become the biocathode. Protons accumulation, which hindered the bioanode operation, thus became an advantage for the biocathode. The bioanodes, formed from garden compost leachate under constant polarization at À0.2 V vs. SCE, were able to support long exposure to forced aeration, with only a slight alteration of their anodic efficiency. They produced a current density of 16 ± 1.7 A/m 2 for acetate oxidation and up to À0.4 A/m 2 for oxygen reduction. Analysis of the microbial communities by 16S rRNA pyrosequencing revealed strong selection of Chloroflexi (49 ± 1%), which was not observed for conventional bioanodes not exposed to oxygen. Chloroflexi were found as the dominant phylum of electroactive biofilms for the first time.

Bidirectional microbial electron transfer: Switching an acetate oxidizing biofilm to nitrate reducing conditions

“…Jeremiasse et al (2012) showed that a mixed culture biofilm could be firstly grown as an acetate-oxidizing bioanode and afterwards switched to a hydrogen-producing biocathode, which certainly decreased the start-up time (>2 times faster). Mixed culture biofilms able to both catalyze organic matter oxidation and oxygen or nitrate reduction have been also described (Blanchet et al, 2014;Cheng et al, 2012Cheng et al, , 2010. However, to the best of the authors' knowledge, the main electron transfer mechanism governing such "switchable" electroactive biofilms has not been elucidated yet.…”

Single medium microbial fuel cell: Stainless steel and graphite electrode materials select bacterial communities resulting in opposite electrocatalytic activities

“…The implementation of microbial anodes and microbial cathodes in a unique electrolyte is completely feasible especially since the demonstration of several electronic exchange mechanisms between reversible electroactive biofilms and electrodes [3,6,44]. These "reversible electrodes" are mostly microbial anodes firstly formed in complex environments (wastewater, activated sludge, garden compost, etc) that under depletion of reducers (e.g.…”

Electrochemical and microbial monitoring of multi-generational electroactive biofilms formed from mangrove sediment

“…The focus on those particular phyla is consistent with previous studies (e.g. [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]) when Proteobacteria and Firmicutes were the predominant ones constituting the biofilms developed in the microbial electrochemical systems.…”

“…Indeed, certain bacterial species, such as Shewanella oneidensis or Pseudomonas aeruginosa, are capable of an extracellular electron transfer that can reach the bacteria composing the electroactive biofilm thanks to secondary electron shuttles (those mediators are oxidized with the cytochromes inserted into the external bacterial membrane, and reduced either directly entering in contact with the working electrode, or with other bacterial cytochromes into the biofilm) [26][27][28][29][30][31].…”

“…The second calculator, called Thetayc calculator, additionally takes into account the OTUs' relative abundance. It was got as follows: S T is the total number of OTUs in communities A and B, a i the relative abundance of OTU i in community A and b i the relative abundance of OTU i in community B. Additionally, Simpson's diversity index (D) was calculated [28]. This index allows measuring the diversity, taking into account both species richness and an evenness of abundance among the species.…”