Electricity Generation in Microbial Fuel Cells at Different Temperature and Isolation of Electrogenic Bacteria

Microbial fuel cell (MFC) is a novel device using biomass and microorganism to produce electricity. Three groups of cube-shaped microbial fuel cells were constructed and operated in fed batch at 30degC, 20degC and 15degC, respectively. The Bacteria present in domestic wastewater were inoculated as the biocatalyst, and 1 g/L glucose was fed as substrate during set-up. While the system was stable, the substrate was replaced with domestic wastewater (320mg COD/L) as sole carbon source. Voltage was affected by temperature obviously: compared to that operated at 30degC (434.3mV), the voltage reduced to 382.8mV at 20degC, and 297.0 mV at 15degC, which was tested under the external resistance of 1000Omega. Power density was decreased 54.9% from 30degC to 15degC (Pmax=367.7mW/m² at 30degC). The coulombic efficiency of 42.2% at 30degC was over two times higher than that in 15degC (CE=18.4%). However, the COD removal rate was only a slight reduction, decreased from 71.4% (30degC) to 66.2% (15degC). The efficient reactors at different temperature were selected and the biofilm attached on the anode was separated with roll tube method under the facultative anaerobic condition. The same configuration of MFCs was used to evaluate the electrochemical activity of electrogenic bacteria with nutrient broth as substrate. 41 strains were totally separated, whose voltage and power density were measured. Two excellent isolates were obtained, FLL2 and FLL3. The voltage of FLL2 and FLL3 were about 210mV, of which the maximum power density were over 65mW/m². The colony characteristic of excellent electrogenic bacteria were generally smooth, flat, round, yellow and opaque. All obtained strains were brevibacteria with pilus, with the topographic height of several microns, observed under scanning electron microscope (SEM).