Response of the microbial community structure of biofilms to ferric iron in microbial fuel cells
Qian Liu, Yang Yang, Xiaoxue Mei, Bingfeng Liu, Chuan Chen, Defeng Xing
State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China.
Ferric iron can affect the current generation of microbial electrochemical system (MES); however, how it influences microbial biofilm formation and metabolic activity has not been reported. Here, we describe the response of microbial electrode biofilm communities to insoluble ferric iron (Fe3+) at different concentrations in microbial fuel cells (MFCs). Insoluble ferric iron (200 μM) improved electrochemical activity of the MFCs microbial biofilms during start-up and resulted in a higher maximum power density of 0.95 W/m2, compared with the control (0.76 W/m2), 500 μM Fe3+ (0.83 W/m2), 1000 μM Fe3+(0.73 W/m2), and 2000 μM Fe3+ (0.59 W/m2) treatments. Illumina Hiseq sequencing of 16S rRNA gene amplicons indicated that the predominant populations in the anode biofilms of the MFCs belonged to Geobacter, with relative abundance of 66–75%. Microbial cathode biofilm communities were more susceptible to Fe3+, as an obvious shift in the cathode biofilm community structures occurred as Fe3+ concentration was increased. The most predominant populations in the MFC cathode biofilms without Fe3+ and with 200 μM Fe3+ were affiliated with Thauera (46% and 35%), whereas no absolutely predominant populations were present in the MFC cathode biofilm with 1000 μM Fe3+. The results demonstrate that a low concentration of Fe3+ facilitated the power output of MFCs and shaped community structures of the electrode biofilm.
Keywords: Microbial fuel cell (MFC), Ferric iron, Electricity generation, Biofilms, Microbial community, Illumina Hiseq sequencing.