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.