Garden compost inoculum leads to microbial bioanodes with potential-independent characteristics

Garden compost leachate was used to form microbial bioanodes under polarization at -0.4, -0.2 and +0.1 V/SCE. Current densities were 6.3 and 8.9 A m(-2) on average at -0.4 and +0.1 V/SCE respectively, with acetate 10 mM. The catalytic cyclic voltammetry (CV) showed similar electrochemical characteristics for all bioanodes and indicated that the lower currents recorded at -0.4V/SCE were due to the slower interfacial electron transfer rate at this potential, consistently with conventional electrochemical kinetics. RNA- and DNA-based DGGE evidenced that the three dominant bacterial groups Geobacter, Anaerophaga and Pelobacter were identical for all bioanodes and did not depend on the polarization potential. Only non-turnover CVs showed differences in the redox equipment of the biofilms, the highest potential promoting multiple electron transfer pathways. This first description of a potential-independent electroactive microbial community opens up promising prospects for the design of stable bioanodes for microbial fuel cells.