Use of a Coculture To Enable Current Production by Geobacter sulfurreducens

Microbial fuel cells often produce more electrical power with mixed cultures than with pure cultures. Here, we show that a cocul-ture of a nonexoelectrogen (Escherichia coli) and Geobacter sulfurreducens improved system performance relative to that of a pure culture of the exoelectrogen due to the consumption of oxygen leaking into the reactor. Microbial communities that develop in microbial fuel cells(MFCs) vary considerably and can depend on the system architecture, inoculum, catholyte, and fuel (organic substrate) (18, 20). Some early studies indicated very diverse anode commu-nities (14), although the MFCs used had very high internal resis-tances which limited power production. Early MFC studies indi-cated low coulombic efficiencies (30%) (24) or did not report data on this (14, 25), so that a substantial amount of substratemay have been lost to processes that did not generate current, such as methanogenesis and aerobic substrate utilization sustained by ox-ygen leaking through the cathode (6, 7, 16, 17). More recently, it has been shown with a variety of substrates that high power generation is usually associated with a large pro