Bacterial growth and respiration in laminar flow microbial fuel cells

Application of micro-scale microbial fuel cells (MFCs) to power electronics is limited due to the high internal resistances associated with membranes. Laminar flow MFCs (LFMFCs) provide an advantage over conventional designs because the anode and the cathode are naturally separated due to the laminar flow regime that develops within the reactor, eliminating the need for membranes. However, our ability to fully harness the potential of LFMFC technology lags from a lack of in-depth understanding of anode/cathode analyte mixing and fundamental factors that maximize LFMFC's power-generating capabilities. We, therefore, investigated the anode colonization and respiration of the known exoelectrogenic bacterium, Geobacter sulfurreducens, in a micro-scale LFMFC. Current production was dependent on the location of the anode relative to the influent in continuous-flow operation, with the highest current density of 6.5 mu A/cm(2) recorded closest to the influent. Lateral diffusion of anode/cathode analytes, in addition to upstream substrate consumption, likely resulted in the observed differences in current production. As current increased, the number of bacterial cells on the anode measured using simultaneous microscopic observation, also increased. Although the current density obtained here was substantially lower than other micro-sized MFCs, these findings show that micro-scale LFMFCs adapted to microscopic observation can provide a unique tool for better understanding real-time anode colonization and overall reactor performance. (C) 2014 AIP Publishing LLC.