title: Kinetic experiments for evaluating the Nernst-Monod model for anode-respiring bacteria (ARB) in a biofilm anode.
abstract: Anode-respiring bacteria (ARB) are able to transfer electrons from reduced substrates to a solid electrode. Previously, we developed a biofilm model based on the Nernst-Monod equation to describe the anode potential losses of ARB that transfer electrons through a solid conductive matrix. In this work, we develop an experimental setup to demonstrate how well the Nernst-Monod equation is able to represent anode potential losses in an ARB biofilm. We performed low-scan cyclic voltammetry (LSCV) throughout the growth phase of an ARB biofilm on a graphite electrode growing on acetate in continuous mode. The (j)V response of 9 LSCVs corresponded well to the Nernst-Monod equation, and the half-saturation potential (E(KA)) was -0.425 +/- 0.002 V vs Ag/AgCl at 30 degrees C (-0.155 +/- 0.002 V vs SHE). Anode-potential losses from the potential of acetate reached approximately 0.225 V at current density saturation, and this loss was determined by our microbial community's E(KA) value. The LSCVs at high current densities showed no significant deviation from the Nernst-Monod ideal shape, indicating that the conductivity of the biofilm matrix (kappa(bio)) was high enough (> or = 0.5 mS/cm) that potential loss did not affect the performance of the biofilm anode. Our results confirm the applicability of the Nernst-Monod equation for a conductive biofilm anode and give insights of the processes that dominate anode potential losses in microbial fuel cells.
authors.affiliation: Center for Environmental Biotechnology, Biodesign Institute at Arizona State University, Tempe, Arizona 85287, USA. cit@asu.edu
authors.forename: César I
authors.initials: CI
authors.lastname: Torres
authors.forename: Andrew Kato
authors.initials: AK
authors.lastname: Marcus
authors.forename: Prathap
authors.initials: P
authors.lastname: Parameswaran
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Rittmann
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D018441:Biofilms; D004566:Electrodes; D007700:Kinetics; D008962:Models, Theoretical