A-Thermophilic-Gram-Negative-Nitrate-Reducing-Bacterium-

AThermophilicGram-NegativeNitrate-ReducingBacterium,Calditerrivibrionitroreducens,ExhibitingElectricityGenerationCapabilityQianFu,†HajimeKobayashi,*,†,‡HideoKawaguchi,†TatsukiWakayama,§HaruoMaeda,§andKozoSato*,†,‡†DepartmentofSystemsInnovation,GraduateSchoolofEngineering,TheUniversityofTokyo,Tokyo,Japan‡EngineeringforSustainableCarbonCycle(INPEXCorporation)SocialCooperationProgram,FrontierResearchCenterforEnergyandResource(FRCER),TheUniversityofTokyo,Tokyo,Japan§INPEXCorporation,9-23-30Kitakarasuyama,Setagaya-ku,Tokyo157-0061,Japan*SSupportingInformationABSTRACT:Toexploitthepotentialdiversityofthermo-philicexoelectrogens,two-chambermicrobialfuelcells(MFCs)wereinoculatedwiththermophilicanaerobicdigestersludgeandoperatedat55°Cwithoutsupplementingwithexogenousredoxmediator.TheMFCgeneratedamaximumpowerdensityof823mWm−2after200hofoperation.Molecularphylogeneticanalysessuggestedthatthemicrobialpopulationontheanodewasdominatedbyaspeciescloselyrelatedtoathermophilicnitrate-reducingbacteriumCaldi-terrivibrionitroreducens,forwhichastrain(Yu37-1)hasbeenisolatedinpureculture.Thus,apurecultureoftheC.nitroreducensstrainYu37-1wasinoculatedintoMFCtoexaminetheelectricitygenerationcapability.Withoutanexogenousmediator,MFCsstablyproducedelectricitywithamaximumpowerdensityof272mWm−2for>400hofoperation.TheMFCcurrentrecoveredtotheoriginallevelwithinfewhoursaftermediumreplacement,suggestingthattheelectricitygenerationwascausedbytheanodicmicroorganisms.Cyclicvoltammetryindicatedthatredoxsystems(E3andEc)withsimilarpotentials(−0.14and−0.17V)madethemaincontributionstotheexoelectrogenicactivitiesofthesludge-derivedconsortiumandC.nitroreducensYu37-1,respectively.ThisstudyundertookthebioelectrochemicalcharacterizationofC.nitroreducensasthefirstexampleofathermophilicGram-negativeexoelectrogen.■INTRODUCTIONThemicrobialfuelcell(MFC)isapromisingenergygeneration/conversiontechnologythatcanbeusedinrenew-ableenergygeneration,wastewatertreatment,biosensing,andbioremediation.1−3AkeyfeatureofMFCsistheuseo