O28-04 : Metabolic Versatility of Electrode-Respiring Geobacter metallireducens Biofilms based on Electrode Potential and Nitrate as a Co-substrate: Key Alternative Metabolisms for Integrated Nitrogen Removal with Bioelectrochemical systems

Kashima Hiroyuki¹,Regan John¹
1Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park
Bioelectrochemical systems (BESs), which have the potential to couple wastewater treatment with renewable energy production, are beginning to be designed for integrated nitrogen removal, but alternative metabolisms of electrode-respiring biofilms that might constrain system performance have been largely overlooked. This research was focused on metabolic capabilities of electrode-respiring Geobacter metallireducens biofilms associated with nitrate, which is the most thermodynamically favorable electron acceptor in anoxic conditions and a key for biological nitrogen removal. Nitrate spike tests to batch-fed BESs operated over a range of anode potentials and biofilm thicknesses showed that nitrate acted as a competitive electron acceptor to the anode, and these facultative metabolisms were controlled by availability of nitrate determined by bulk nitrate concentration and its diffusion into a biofilm, but not by anode availability determined by anode potential. In addition, biofilms reversibly used an electrode as an electron donor or acceptor as a function of electrode potential and availability of nitrate with quick metabolic shifts (~ 1 hour). Increased nitrate-reducing enzyme activity of anode-reducing cells without prior nitrate exposure inferred a nature of electrode-respiring cells preparing an alternative metabolic option.

keywords:biofilm,engineered biofilm,facultative metabolisms,Geobacter,electrode