Improving power production in acetate-fed microbial fuel cells via enrichment of exoelectrogenic organisms in flow-through systems

Abstract

An exoelectrogenic, biofilm-forming microbial consortium was enriched in an acetate-fed microbial fuel cell (MFC) using a flow-through anode coupled to an air-cathode. An MFC design with low electrode spacing, high specific electrode surface area with minimal dead volume and control of external resistance was used. In addition, continuous feeding of carbon source was employed and the MFC was operated at intermittent high flows to enable removal of non-biofilm-forming organisms over a period of 6 months. The consortium enriched using the modified design and operating conditions resulted in a power density of 345 W m⁻³ of net anode volume (3650 mW m⁻²), when coupled to a ferricyanide cathode. The enriched consortium included β-, δ-, γ-Proteobacteria, Bacteroidetes and Firmicutes. Members of the order Rhodocyclaceae and Burkholderiaceae (Azospira sp. (49%), Acidovorax sp. (11%) and Comamonas sp. (7%)), dominated the microbial consortium. Denaturing gradient gel electrophoresis (DGGE) analysis based on primers selective for archaea indicated presence of very few methanogens. Limiting the delivery of the carbon source via continuous feeding corresponding to the maximum cathodic oxidation rates permitted in the flow-through, air-cathode MFC resulted in coulombic efficiencies reaching 88 ± 5.7%.