Anode potential regulates microbial competition between anode-respiring bacteria and methanogens in the biofilm anode

Single-chamber microbial electrolysis cells (MECs) seem promising for renewable H ₂ generation, because they minimize the ohmic over-potential by eliminating the membrane. However, H ₂ produced at the cathode can be consumed by H ₂-oxidizing microorganisms in the single-chamber MECs, with CH ₄ being a significance H ₂ sink. Thus, suppressing methanogenesis is a key for high-yield H ₂ production in single-chamber MECs. Anode-respiring bacteria gain energy from the potential difference between donor substrate and their terminal intracellular electron carrier. Anode potential (Eanode) should regulate the potential for the terminal carrier, and the carrier's potential must be more negative than the anode potential to allow electron flow. We evaluated CH ₄ formation in a single-chamber MEC at Eanode values from -0.03 to -0.23 V vs. SHE. Electron balances showed that CH4 was the largest electron sink, consuming from 11% to 28% of acetate electrons as E _anode was decreased from -0.03 V to -0.23 V.