Microbial kinetics of anode-respiring bacteria

Anode-respiring bacteria (ARB) are of special importance for their ability to directly generate an electrical current from organic compounds, by transferring electrons from the substrate to a solid anode. Using microbial fuel cells or electrolysis cells (MXCs), ARB can be utilized to convert organic wastes into a renewable energy source. Various processes were characterized that determine the microbial kinetics of ARB, including substrate consumption, electron transport and proton transport. Of the various substrates tested, ARB in our system were able to consume acetate most effectively, while other substrates, such as ethanol, appeared to be fermented to acetate and hydrogen before being consumed by ARB.;Proton transport proved to be an important kinetic limitation under typical experimental conditions, which resulted in a decrease in pH inside the biofilm anode and ARB inhibition. On the other hand, extracellular electron transport (EET) carried out by ARB was fast and was carried out with minimal potential losses, as characterized by electrochemical data fitting using the Nernst-Monod relationship. The fast EET kinetics demonstrates ARB's ability to produce an extracellular conductive matrix that is able to transfer electrons from the ARB to the anode surface with minimal potential losses. Using an electrochemical control of the anode potential, ARB communities were selected from wastewater that are able to produce high current densities at low anode potentials, which is an important requirement for MXC feasibility. The characterization of ARB kinetics will be an invaluable tool for the development of MXC commercial applications.