An algae bioreactor (ABR) was externally connected to air-cathode microbial fuel cells (MFCs) to increase power generation by supplying a high amount of oxygen to cathode electrode. The MFC with oxygen fed from ABR produced maximum cell voltage and cathode potential at a fixed loading of 459 mV and 10 mV, respectively. During polarization analysis, the MFC displayed a maximum power density of 0.63 W/m(2) (at 2.06 A/m(2)) using 39.2% O-2 from ABR, which was approximately 30% higher compared with use of atmospheric air (0.44 W/m2, 20.8% O-2,). The cyclic voltammogram analysis exhibited a higher reduction current of -137 mA with 46.5% O-2 compared to atmospheric air (-115 mA). Oxygen supply by algae bioreactor to air-cathode MFC could also maintain better MFC performance in long term operation by minimizing cathode potential drop over time. (C) 2015 Elsevier Ltd. All rights reserved.