Essential-Data-and-Techniques-for-Conducting-Microbial

DOI:10.1002/cssc.201100604EssentialDataandTechniquesforConductingMicrobialFuelCellandotherTypesofBioelectrochemicalSystemExperimentsBruceE.Logan*[a]IntroductionStudiesofelectrochemicalactivitiesofmicroorganismshavein-creasedbothinnumberandcomplexityoverthepast100years.ThefirststudieswereconductedbyPotter[1,2]overonehundredyearsagoatauniversityintheUKthatiscurrent-lyknownasNewcastleUniversity.Potterusedaverysimplesystem(Figure1)toshowthatanelectrochemicalpotentialwasgeneratedbydifferentmicrobeswhentheyweregivencertainorganicsubstrates.HefoundpotentialsweregeneratedbytheyeastSaccharomycescerevisiaeandthebacteriumBacil-luscoli(laterrenamedEscherichiacoli[3]),bothofwhichfer-mentedsubstratesinthemedium.Hefailedtomeasureanyelectromotiveforcegeneratedwiththreeothermicroorgan-isms,buttheseothermicrobesdidnotgrowinthemedium.Fermentativegrowthofmicroorganismscansetupthermody-namicpotentialsintermsofsubstrates,pHandothergradi-ents,[4,5]whichcanoftenleadtothegenerationofanelectro-motiveforce,butnotappreciablecurrentgeneration.Onlymi-croorganismsthatgeneratesubstantialcurrentdensitieswith-outtheuseofexogenouselectronshuttlesormediators,calledexoelectrogens,areofprimaryinteresttoday.SincethisfirststudybyPotter,[1]over3000papershavebeenwritteninthegeneralareaofbioelectrochemicalsystems(basedonaThomsonReutersWebofSciencesearch),mostlyinthefieldofmicrobialfuelcells(MFCs),andtheequipmentneededtoconducttheseexperimentshasbeensubstantiallyadvanced.IncontrasttosimplecircuitsandmaterialsusedbyPotter,amodernbioelectrochemicallaboratorywillusemanydifferentinstrumentsforobtainingdata,suchasmultimetersforlowimpedancevoltagemeasurementsandpotentiostatsforelectrochemicalanalysis(Figure1).Aswelearnmoreaboutfactorsthataffectthegenerationofelectricalcurrentusingmi-croorganisms,ithasbecomeapparentthatbettercontrols,measurements,andcareareneededwhentakingmeasure-mentsandreportingresults.TheexperimentsbyPotterareagoodexampleinthisregard.BothS.cerevisiaeandE.coliarenotconsideredtobeexoelectrogenicmic