DUGi

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

http://dugi.udg.edu/item/http:@@@@hdl.handle.net@@10256@@13144

Up to date a few electroactive bacteria embedded in biofilms are described to catalyze both anodic and cathodic reactions in bioelectrochemical systems (i.e. bidirectional electron transfer). How these bacteria transfer electrons to or from the electrode is still uncertain. In this study the extracellular electron transfer mechanism of bacteria within an electroactive biofilm was investigated by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). First, a mature anodic electroactive biofilm was developed from an activated sludge sample (inoculum), acetate as electron donor and a poised electrode (+397. mV vs. SHE). Later, this biofilm was "switched" to biocathodic conditions by feeding it with a medium containing nitrates and poising the electrode at -303. mV vs. SHE. The electrochemical characterization indicated that both, acetate oxidation and nitrate reduction took place at a similar formal potential of -175±05 and -175±34. mV vs. SHE, respectively. The biofilm was predominantly composed by Geobacter sp. at both experimental conditions. Taken together, the results indicated that both processes could be catalyzed by using the same electron conduit, and most likely by the same bacterial consortium. Hence, this study suggests that electroactive bacteria within biofilms could use the same electron transfer conduit for catalyzing anodic and cathodic reaction

This work was supported by the Spanish Government (CTQ2014 SGR-1168,CTQ2014-53718-R). A.A.C.M.was supported by the French National Research Agency (Project:ANR‐10‐BTBR‐02). N.P. was supported by the Catalan Government (2012FI B00941). The authors acknowledge the scientific contribution of Pau Batlle-Vilanova (LEQUIA-UdG)

Elsevier