BIOTECHNOLOGICAL PRODUCTS AND PROCESS ENGINEERING Application of biocathode in microbial fuel cells: cell performance and microbial community Guo-Wei Chen & Soo-Jung Choi & Tae-Ho Lee & Gil-Young Lee & Jae-Hwan Cha & Chang-Won Kim Received: 29 January 2008 / Revised: 26 February 2008 / Accepted: 9 March 2008 / Published online: 2 April 2008 # Springer-Verlag 2008 Abstract Instead of the utilization of artificial redox mediators or other catalysts, a biocathode has been applied in a two-chamber microbial fuel cell in this study, and the cell performance and microbial community were analyzed. After a 2-month startup, the microorganisms of each compartment in microbial fuel cell were well developed, and the output of microbial fuel cell increased and became stable gradually, in terms of electricity generation. At 20 ml/min flow rate of the cathodic influent, the maximum power density reached 19.53 W/m 3 , while the corresponding current and cell voltage were 15.36 mA and 223 mV at an external resistor of 14.9 Ω, respectively. With the develop- ment of microorganisms in both compartments, the internal resistance decreased from initial 40.2 to 14.0 Ω, too. Microbial community analysis demonstrated that five major groups of the clones were categorized among those 26 clone types derived from the cathode microorganisms. Betaproteo- bacteria was the most abundant division with 50.0% (37 of 74) of the sequenced clones in the cathode compartment, followed by 21.6% (16 of 74) Bacteroidetes, 9.5% (7 of 74) Alphaproteobacteria, 8.1% (6 of 74) Chlorobi, 4.1% (3 of 74) Deltaproteobacteria, 4.1% (3 of 74) Actinobacteria, and 2.6% (2 of 74) Gammaproteobacteria. Keywords Microbial fuel cells . Biocathode . Cell performance . Microbial community Introduction Microbial fuel cell (MFC) that utilizes wastewater or convertible biomass as fuel is a promising technology to carry out energy recovery and pollution control (Angenent et al. 2004; Kim et al. 2007a, b; Logan et al. 2006; Rabaey and Verstraete 2005; Rittmann 2006; Tender et al. 2002). Compared to the traditional secondary transformation of energy, this direct conversion from primary fuel to electricity makes it possible to achieve a higher efficiency theoretically (Logan 2004; Rabaey and Verstraete 2005). However, there are still several bottlenecks encountered in their practice application and scale-up, such as the limitation of electron transfer between microorganisms and electrodes, membrane resistance in the proton trans- portation process, various overpotential, unsatisfactory mixing, and turbulence in each compartment (Logan et al. 2006; Rabaey and Verstraete 2005). Researchers have been making effort to solve those problems. Different electrode materials have been tested in MFC to decrease the activation overpotential and their structures, such as carbon paper, carbon felt, carbon brush, carbon fiber, graphite of various type, Pt, Cu, Cu– Au, tungsten carbide, and so on (Bullen et al. 2006; Kargi and Eker 2007; Liu et al. 2004; Logan et al. 2007; Park et al. 2007; Rosenbaum et al. 2006). Another alternative is the application of catalysts onto the cathode by coating technique. It is common to use Pt as cathode catalyst, while other polymer binders have also been tested, such as perfluorosulfonic acid (Nafion), poly tetrafluoroethylene, and the noble-metal free eclectrocata- Appl Microbiol Biotechnol (2008) 79:379–388 DOI 10.1007/s00253-008-1451-0 G.-W. Chen : S.-J. Choi : T.-H. Lee : G.-Y. Lee : J.-H. Cha : C.-W. Kim (*) Department of Environmental Engineering, Pusan National University, Busan, 609-735, South Korea e-mail: cwkim@pusan.ac.kr G.-W. Chen School of Civil Engineering, Hefei University of Technology, Hefei, 230009, China