In the course of microbial fuel cell (MFC) operation, the acidification of the anode and the alkalization of the cathode inevitably occur, resulting in reduction of the overall performance. In an attempt to reverse the membrane pH gradient, a tubular air-cathode two-chamber MFC was developed that allowed pH adjustment in both compartments. With an anodic pH of 10.0 and a cathodic pH of 2.0, the tubular MFC provided an open circuit voltage of 1.04 V and a maximum power density of 29.9 W/m(3), which were respectively 1.5 and 3.8 times higher than those obtained in the same MFC working at neutral pH. Particularly, the suppression of methanogenesis at high alkaline anode (pH 10.0) contributed to a significant enhancement in coulombic efficiency. The MFC maintained 74% of its performance after 15 days of operation in continuous-flow mode. The appropriate pH adjustment strategy in both compartments ensures a promising improvement in MFC performance. (c) 2009 Elsevier Ltd. All rights reserved.