The performance of a prototype up-flow single-chambered microbial fuel cell (MFC) for electrical power generation using brewery wastewater as fuel is reported. The designed reactor consisted of three zones, namely a lower anaerobic digestion zone, a central MFC zone, and an upper effluent clarifier zone. Tests were conducted in batch mode using a beer wastewater as the fuel/electron donor (CODd concentration: 430 mg/L) and mixed consortia (both sewage microflora and anaerobic sludge) as a source of electrogenic bacteria. A stable current density of similar to 2,270 mA/m(2) was generated under continuous polarization with a constant external resistance (0.01 k Omega) and cell polarization gave a peak power density of 330mW/m(2) at a current density of 1,680 mA/m(2). Electrochemical impedance analysis showed that the overall internal resistance of the reactor was quite low, that is, 8.0 Omega. Cyclic voltammetric analysis of the anodic biofilm at low scan rate revealed quite complex processes at the anode, with three redox peaks, at potentials of 116, 214, and 319mV (vs. NHE). Biotechnol. Bioeng. 2010; 107: 52-58. (C) 2010 Wiley Periodicals, Inc.