Charge storage and electron transfer kinetics in Geobacter sulfurreducens biofilms

BONANNI, PABLO SEBASTIAN; SCHROTT, GERMÁN DAVID; ROBUSCHI, LUCIANA; BUSALMEN, JUAN PABLO

Norwich

Congreso; Electron transfer at the microbe-mineral interface; 2012

University of East Anglia

Respiration of cells forming electro-active biofilms has been recently demonstrated to continue after the interruption of electrode polarization (lack of electron acceptor), thanks to the possibility of these bacteria to store electrons in the haem groups of its exo-cytoplasmic cytochromes. Interestingly, it has been shown that stored electrons can be recovered as a transient current when the electrode is connected again. In this work we present a model for biofilm electron transfer that reproduces the transient current obtained upon electrode reconnection. The model allows the estimation of rate constants for processes involved in electron transport from the substrate to the electrode, as well as the distribution of charge storing sites within the biofilm.Results indicate that processes involved in electron transfer from acetate to cell internal cytochromes represent the main limitation for current production and show that both, electron transport through the matrix of external cytochromes and interfacial electron transfer are orders of magnitude faster than the cell internal step. Charge storage was found to be one order of magnitude higher inside the cells compared with that in the conductive matrix.