Combining microbial cultures for efficient production of electricity from butyrate in a microbial electrochemical cell

•Two complementary mixed cultures were identified and combined in an MXC.•The combined culture was capable of producing current from butyrate, via acetate.•The combined culture rivals enriched cultures in current density and efficiency.•We identified the organisms responsible for both acetate and current production.•The right microbial partners can perform complex processes in MXCs.

Butyrate is an important product of anaerobic fermentation; however, it is not directly used by characterized strains of the highly efficient anode respiring bacteria (ARB) Geobacter sulfurreducens in microbial electrochemical cells. By combining a butyrate-oxidizing community with a Geobacter rich culture, we generated a microbial community which outperformed many naturally derived communities found in the literature for current production from butyrate and rivaled the highest performing natural cultures in terms of current density (∼11 A/m2) and Coulombic efficiency (∼70%). Microbial community analyses support the shift in the microbial community from one lacking efficient ARB in the marine hydrothermal vent community to a community consisting of ∼80% Geobacter in the anode biofilm. This demonstrates the successful production and adaptation of a novel microbial culture for generating electrical current from butyrate with high current density and high Coulombic efficiency, by combining two mixed microbial cultures containing complementing biochemical pathways.