Screening Of High Active Electricigen And Its Power Performance Analysis In Microbial Fuel Cells

Microbial fuel cell (MFC) is a kind of novel equipment that oxidizes organic compound and directly converts chemical energy into electricity using microorganisms as the catalysts. The direct conversion from biochemistry energy to electrical energy is achieved by MFCs, which combines the fuel cells with biological technology. Recently, MFCs exhibits the wide application prospect in releasing energy shortage, wastewater resources treatment and other aspects.In the previous study, the sludge from TEDA Sewage Treatment Plant (Tianjin) was inoculated into the single MFCs. After 14d running, the thick biofilm enriched in the anode was clearly observed, which was then used as the object to isolate the microorganisms with electrochemical activity in this paper. It was found that 13 strains were obtained by the cultivation method. The electricity production capacity of each strain was further estimated by MFCs using the voltage value as an index. Finally, the strain P2-A-1 was screened and identified as T. osonensisa based on the morphological observation, biochemical and physiological characteristics, fatty acid composition analysis and 16S rDNA sequence information.The electricity production performance of strain T. osonensisa P2-A-1 were further improved by optimizing the initial cell concentration in the inoculation medium, the type and concentration of the substrates in the anolyte, the pH of acolyte, external resistance, the buffer solution of anolyte, as well as the cell permeabilization using chemical agents. Results showed that the optimal operation process was as follows:strain T. osonensisa P2-A-1 was inoculated into TSB liquid medium and statically incubated at 22? under aerobic conditions. After 48h of incubation, the OD600 of culture reached 2.714. The cells were harvested by centrifugation, treated by 1mM EDTA for 20min and then added into the anolyte III(PBBM liquid medium containing 2.000 g/L sodium acetate as the substrate and 5.000 g/L ferric citrate as the electron donor, pH 7.2) to form the inoculation medium with the dry cell concentration of 3.394g/L. It was inoculated into the MFCs connecting the external resistance 1000?. After 14d running at the room temperature, the power density of MFCs reached 509mW/m2, which was increased by 162.4% compared with the original level (194mW/m2).The reasons for the increased power density of strain T. osonensisa P2-A-1 in MFCs were analyzed by observing the ultramicroscope structure of bacteria, measuring the content of key electronic carrier CoQ10, detecting the composition of fatty acids under the EDTA treatment. It was found that the change on cell morphology increased the adhesion of bacteria on the electrode, which made the bacteria/electrode surface more rapid electron transfer ability. In addition, the increase of the key electronic carrier CoQ10 content and the enhancement of cell permeability induced by the modification on fatty acid composition could result in the improvement of power density. This is the first time for T. osonensis intraspecific microbe which shows electrochemical activity and is applied in MFCs. Compared with other electricigen, the electricity production capacity of T. osonensisa P2-A-1 is less than that of strictly anaerobic electricigens, but significantly higher than that of facultative anaerobic electricigens.The research achievement is of important guidance for enriching the diversity of electricigens, discovering more microbes with high electrochemical activity, improving the electricity production performance and exploring the electricity production mechanism.