Enhanced Electricity Production by Use of Reconstituted Artificial Consortia of Estuarine Bacteria Grown as Biofilms

Microbial fuel cells (MFCs) can convert organic compounds directly into electricity by catalytic oxidation, and although MFCs have attracted considerable interest, there is little information on the electricity-generating potential of artificial bacterial biofilms. We have used acetate-fed MFCs inoculated with sediment, with two-chamber bottles and carbon cloth electrodes to deliver a maximum power output of similar to 175 mW.m(-2) and a stable power output of similar to 105 mW.m(-2). Power production was by direct transfer of electrons to the anode from bacterial consortia growing on the anode, as confirmed by cyclic voltammetry (CV) and scanning electron microscopy (SEM). Twenty different species (74 strains) of bacteria were isolated from the consortium under anaerobic conditions and cultured in the laboratory, of which 34% were found to be exoelectrogens in single-species studies. Exoelectrogenesis by members of the genera Vibrio, Enterobacter, and Citrobacter and by Bacillus stratosphericus was confirmed, by use of culture-based methods, for the first time. An MFC with a natural bacterial consortium showed higher power densities than those obtained with single strains. In addition, the maximum power output could be further increased to similar to 200 mW.m(-2) when an artificial consortium consisting of the best 25 exoelectrogenic isolates was used, demonstrating the potential for increased performance and underlying the importance of artificial biofilms for increasing power output.