Microbial fuel cell is one of the most convenient and cost-effective technology for producing the clean energy. This study explores the exoelectrogenic behavior of Pichia fermentans in a microbial fuel cell. Two different reactor designs (double- and single-chambered) were tested in the presence and in the absence of a mediator (methylene blue). The influence of extracellular polymeric substances in the electricity generation has also been studied. In a double-chambered setup, maximum open circuit voltages were measured as 0.602 and 0.488 V with mediator and without mediator cell, respectively, whereas maximum power densities were measured as 1.23 mu Wcm(-2) and 0.407 mu Wcm(-2), respectively. In addition, maximum open circuit voltages were observed as 0.40 and 0.397 V in a single-chambered fuel cell with and without mediator, respectively. The maximum power density was recorded 1.64 mu Wcm(-2) in the presence of a mediator, whereas the same was found as 0.643 mu Wcm(-2) in the absence of mediator. Thus, these results indicate that P. fermentans has the ability to produce high power density under microaerophilic conditions with mediator in a single-chambered membrane less setup. (C) 2018, The Society for Biotechnology, Japan. All rights reserved.