EST200943380385英文污水文献

QuorumSensing:ANewBiofoulingControlParadigminaMembraneBioreactorforAdvancedWastewaterTreatmentKYUNG-MINYEON,†WON-SEOKCHEONG,†HYUN-SUKOH,†WOO-NYOUNGLEE,†BYUNG-KOOKHWANG,†CHUNG-HAKLEE,*,†HALUKBEYENAL,‡ANDZBIGNIEWLEWANDOWSKI§SchoolofChemicalandBiologicalEngineering,SeoulNationalUniversity,Seoul151-744,Korea,SchoolofChemicalEngineeringandBioengineering,WashingtonStateUniversity,Pullman,Washington99164-2710,andCenterforBiofilmEngineering,MontanaStateUniversity,Bozeman,Montana59717-3980ReceivedJuly17,2008.RevisedmanuscriptreceivedOctober18,2008.AcceptedNovember5,2008.Bacteriaregulatespecificgroupbehaviorssuchasbiofilmformationinresponsetopopulationdensityusingsmallsignalmoleculescalledautoinducers(quorumsensing,QS).Inthisstudy,theconceptofbacterialQSwasappliedtomembranebioreactors(MBRs)foradvancedwastewatertreatmentasanewbiofoulingcontrolparadigm.Theresearchwasconductedinthreephases:(1)demonstratethepresenceoftheautoinducersignalinMBRs,(2)correlateQSactivityandmembranebiofouling,(3)applyQS-basedmembranebiofoulingcontrol.AbioassaywithAgrobacteriumtumefaciensreporterstrainprovedthatN-acylhomoserinelactone(AHL)autoinducerswereproducedintheMBR.Furthermore,thin-layerchromatographicanalysisidentifiedatleastthreedifferentAHLsinthebiocake,ofwhichN-octanoyl-homoserinelactonewasthemostabundant.DuringcontinuousMBRoperation,thebiocakeshowedstrongAHLactivitysimultaneouslywithabruptincreaseinthetransmembranepressure,whichimpliesthatQSisincloseassociationwithmembranebiofouling.PorcinekidneyacylaseI,whichcaninactivatetheAHLmoleculebyamidebondcleavage,wasconfirmedtopreventmembranebiofoulingbyquenchingAHLautoinducers.Fromtheseresults,itwasconcludedthatQScouldbeanoveltargetforbiofoulingcontrolinMBRs.IntroductionOverthepasttwodecades,themembranebioreactor(MBR)hasemergedasoneoftheinnovativetechnologiesinadvancedwastewatertreatment.Recentstudieswithad-vancedmolecularbiologicaltechniqueshaverevealedthatthecharacteristicsofthebiocakeformedonthemembrane,suchasporosity(1)andbiovolume(2),arecloselyassociatedwiththepermeabilityloss(membranebiofouling)inMBRs.Althoughvariousbiofoulingcontroltechniqueshavebeendevelopedthroughengineering(3),material(4),andchem-istryapproaches(5),alltheseattemptshavethelimitationthattheyareessentiallynotabletopreventthebiofilmformationbecauseitisintrinsicallyanaturalbiologicalprocess.Inthisstudy,theconceptofbacterialquorumsensing(QS)wasappliedtoanMBRforthecontrolofmembranebiofouling.Bacteriaproducesmallmoleculescalledauto-inducersforthepurposeofintercellularcommunication.Whentheautoinducerconcentrationreachesthethresholdlevelinproportiontothecelldensity,itcombineswiththereceptorproteinandactivatesthetranscriptionofspecificgenestoinducegroupbehaviorssuchasbioluminescence(6),antibioticproduction(7),virulence(8),biofilmformation(9)andsporulation(10).SinceDaviesandcolleagues(9)firstdemonstratedthataQSmechanismwasinvolvedinthedifferentiationofPseudomonasaeruginosabiofilmformation,manystudieshavereportedthatQScontrolcansuccessfullyreduceorpreventbiofilmformationonsurfacessuchasmedicaldevices(11)andplanttissue(12).Theseresultsenabledustohypothesizethat,inprinciple,membranebiofoulingoriginatingfrombiofilmformationcouldalsobealleviatedthroughQScontrol,e.g.,theblockingofintercellularcommunicationtoobtainMBRsofhighperformance(Figure1).Noinformation,however,isavailableontheapplicationofQStobiofoulingcontrolinMBRs.Inthisstudy,wedevelopedanovelbiofoulingcontrolparadigminanMBRbasedontheconceptofQS.Toachievethisgoal,theoverallexperimentswereconductedinthreephases:(1)demon-stratingthepresenceofanautoinducerintheMBR,(2)showingacorrelationbetweenQSactivityandmembranebiofouling,and(3)developingQS-basedmembranebio-foulingcontroltechniques.ItisworthnotingthatthebiofoulinglayeronthemembranesurfaceinanMBRconsistsofbothdepositedmicrobialflocs(e.g.,MLSS)andgrowingmicroorganismsonthemembranesurface(e.g.,biofilm).Toavoidconfusion,thedepositedMLSSisdifferentiatedfromthebiofilmandtheterm“biocake”isusedtorepresentthewholebiofoulinglayer,e.g.,thecombinationofdepositedMLSSandbiofilm(13).ExperimentalSectionMicroorganisms.AgrobacteriumtumefaciensA136(Ti-)-(pCF218)(pCF372)wasusedasareporterstrainforN-acylhomoserinelactone(AHL)autoinducersofGram-negativebacteria(14).TheAHLdetectionmechanismofA.tumefaciensA136isdescribedintheSupportingInformation.Briefly,this*Correspondingauthortel.:[phone];fax:[phone];e-mail:[e-mail].†SeoulNationalUniversity.‡WashingtonStateUniversity.§MontanaStateUniversity.FIGURE1.ConceptofQS-basedbiofoulingcontrolinMBR.Environ.Sci.Technol.2009,43,380–3853809ENVIRONMENTALSCIENCE&TECHNOLOGY/VOL.43,NO.2,200910.1021/es8019275CCC:$40.752009AmericanChemicalSocietyPublishedonWeb12/18/2008reporterstraindevelopsabluecoloronanagarplatecoveredwithX-gal(5-bromo-4-chloro-3-indolyl-beta-D-galactopy-ranoside)inresponsetoexogenousAHLmolecules.A.tumefaciensA136wasculturedonLuria-Bertani(LB)brothsupplementedwithspectinomycinandtetracyclinetomain-taintwoplasmidsthatprovidetheAHLresponsesystem(15).ActivatedsludgefromtheSi-Hwawastewatertreatmen