Shewanella Haliotis Z4and Enterococcus Faecalis Z5and Their Characteristics Of Electricity Generation

Microbial fuel cells （MFCs）, one of new techniques, can convert biomass energy intoelectricity and are focused by people. Microorganisms in MFCs play very important roles ascatalysts. So far, there has been an increase in recent years in the number of reports of over20species that can generate electricity in microbial fuel cells, but understanding of those stillare limited. In the study, the anodic biofilm was enriched a glucose-fed single chamber aircathode MFC, operated in batch mode inoculated with mangrove sediment. Twoexoelectrogens were isolated, screened and identified from the anode biofilm combined withthe three-electrode system electrochemical methods. The physiological, biochemical andelectricity-generating characteristics of of the two isolated strains were explored. The mainresults were as follows.（1） Twenty-three isolations were isolated from the anodic biofilm of MFC-a withmangrove sediment, of which cyclic voltammograms （CVs） of four strains had more obviousredox peaks. The result of16S rDNA molecular identification demonstrated that the threeisolated strains, named Z4, had high sequence similarity with Shewanella haliotis strainDW01（100%）, and a strain, named Z5, had high sequence similarity with Enterococcusfaecalis JCM5803（100%）.（2） Bacterial culture exponential phase of strain Z4was from5h to22h after beinginoculated. CV of centrifuged cell suspension of strain Z4at exponential phases showed twodistinct redox peaks at-1.426V and1.38V, respectively. When strain Z4was employed intoMFC-1with sodium lactate as the electron donor, the maximum power density, stable outputvoltage, internal resistance and electricity-generating cycle were274mW m^-2,0.279V,900and about16h, respectively. The difference between cathode potential and anode potential ofMFC-1was only0.008V at stable period of electricity generation. CV of anode filtered brothin MFC-1with two oxidization peaks and three reduction peaks, which showed one moreoxidization peak and two more reduction peaks than that of cell suspension of strain Z4. TheMFC electricity generating experiment inoculating with strain Z4using many kinds ofsubstrates showed that the stable output voltage and maximum power density reached maximums of0.279V and274mW m^-2, respectively, with sodium lactate as the substrate.However, coulomb efficiency reached a maximum of77.30%when sodium formate was usedas the electron donor.（3） Bacterial culture exponential phase of strain Z5was from5h to19h after beinginoculated. CV of centrifuged cell suspension of strain Z5at exponential phases showed twodistinct redox peaks at-1.485V and1.912V, respectively. When strain Z5was employed intoMFC^-2 with sodium lactate as the electron donor, the maximum power density, stable outputvoltage, internal resistance and electricity-generating cycle were382mW m^-2,0.302V,1000Ω and about14h, respectively. The difference between cathode potential and anode potential ofMFC^-2 was only0.004V at stable period of electricity generation. CV of anode filtered brothin MFC^-2 revealed no redox peak at all, demonstrating strain Z5maynot use excretedmediators to transfer electrons. The MFC electricity generating experiment from variouskinds of substrates showed the stable output voltage, maximum power density and coulombefficiency reached maximums of382mW m^-2,0.302V, and15.86%, respectively, with sodiumlactate as the substrate.