Decolorization of acid and basic dyes understanding the meta

Decolorization of acid and basic dyes understanding the metabolic degradation and cell

ApplMicrobiolBiotechnol

DOI10.1007/s00253-015-6648-4

ENVIRONMENTALBIOTECHNOLOGY

Decolorizationofacidandbasicdyes:understandingthemetabolicdegradationandcell-inducedadsorption/precipitationbyEscherichiacoli

MatteoCerboneschi1&MassimoCorsi2&RobertoBianchini2&MarcoBonanni2&StefaniaTegli1

Received:11February2015/Revised:16April2015/Accepted:19April2015#Springer-VerlagBerlinHeidelberg2015

AbstractEscherichiacolistrainDH5αwassuccessfullyemployedinthedecolorizationofcommercialanthraquinoneandazodyes,belongingtothegeneralclassesofacidorbasicdyes.ThebacteriashowedanaptitudetosurviveatdifferentpHvaluesonanydyesolutiontested,andarapiddecoloriza-tionwasobtainedunderaerobicconditionsforthewholecol-lectionofdyes.AdeepinvestigationaboutthemodeofactionofE.coliwascarriedouttodemonstratethatdyedecoloriza-tionmainlyoccurredviathreedifferentpathways,specificallybacterialinducedprecipitation,cellwalladsorption,andme-tabolism,whoseweightwascorrelatedwiththechemicalna-tureofthedye.Inthecaseofbasicazodyes,anunexpectedfastdecolorizationwasobservedafterjust2-hpostinoculationunderaerobicconditions,suggestingthatmetabolismwasthemainmechanisminvolvedinbasicazodyedegradation,asunequivocallydemonstratedbymassspectrometricanalysis.ThereductivecleavageoftheazogroupbyE.colionbasicazodyeswasalsofurtherdemonstratedbytheinhibitionofdecolorizationoccurringwhenglucosewasaddedtothedyesolution.Moreover,noresidualtoxicitywasfoundintheE.coli-treatedbasicazodyesolutionsbyperformingDaphniamagnaacutetoxicityassays.Theresultsofthepresentstudy

ElectronicsupplementarymaterialTheonlineversionofthisarticle(doi:10.1007/s00253-015-6648-4)containssupplementarymaterial,whichisavailabletoauthorizedusers.*MatteoCerboneschi

matteo.cerboneschi@unifi.it

1

demonstratedthatE.colicanbesimplyexploitedforitsnat-uralmetabolicpathways,withoutapplyinganyrecombinanttechnology.Thehighversatilityandadaptabilityofthisbac-teriumcouldencourageitsinvolvementinindustrialbioreme-diationoftextileandleatherdyeingwastewaters.KeywordsEscherichiacoli.Bacteria.Dyes.

Bioremediation.Azoreductase.Decolorization.Aerobicmetabolism.Celladsorption.Toxicity

Introduction

Acidandbasicdyesaresomeofthemostextensivelyusedcolorantswithinthetextileandleatherindustry(Hunger2002).Theirwideapplicationinvolvesroutinedyeingproce-dures,whichmaydifferamongdyersforthenumberofstepsand/orchemicalauxiliariesusedtofavordyeinghomogeneity(Shore2002).Asaresultofthelargenumberanddifferentnatureofthechemicalsused,thewastewatersgeneratedfromthedyeingoftextileandleathermaterialsaresomeofthemajorpollutingchemicalcontainingwastes(Claudio2007;Slater2003).Althoughprogresseshavebeenmadetoreplacethechemicalauxiliarieswithnaturalorsemisyntheticsub-stancesinaviewtogeneratingmoreenvironmentallyfriendlywastewaters(deSousaetal.2011),thetraditionaldyesarestillinuseandrepresentoneofthemainsourcesofpollutionforwaterstreams(Alinsafietal.2007).Thesedyescauseseriousenvironmentalandhealthconcernstoaqueousecosystemsandhumans(SarnaikandKanekar1995),duetotheirtoxicity(deCamposVentura-CamargoandMarin-Morales2013).Typically,dyeingbathscontainanominalpercentageofdyebetween1and15%byweightofmaterial,but2upto50%oftheoriginaldyeisgenerallylostinthewastewaters,dependingontheclassofthedyeused(Khanetal.2013;Ogugbue

and

DipartimentodiScienzedelleProduzioniAgroalimentariedell’Ambiente,LaboratoriodiPatologiaVegetaleMolecolare,UniversitàdegliStudidiFirenze,SestoFiorentino(Firenze),ItalyDipartimentodiChimicaBUgoSchiff^,UniversitàdegliStudidiFirenze,SestoFiorentino(Firenze),Italy

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Sawidis2011;Khalidetal.2008;McMullanetal.2001).Inparticular,theglobalannualproductionofleatherandtextiledyesis7×105T,foranannualtradeoftheseindustriesthatisover2and70milliontons,respectively(TheFreedoniaGroup2013;ZahariaandSuteu2012).Therefore,theenvironmentalimpactoftheeffluentsfromthedyeingindustryisaseriousconcern.Inaddition,thedisposalofdyeingeffluentsconsti-tutesthelargestportionofthecostsassociatedtowaterman-agement(Slater2003).Varioustreatmentsfordye-containingwastewatershavebeendeveloped,toaddresstheseenviron-mentalandeconomicalissues:mainlychemicalandelectro-chemicaloxidation,filtrationonmicromembranes,precipita-tionofdyesintheformofinsolublesalts,photocatalyticdeg-radation,andadsorptionorelectrosorption(SinghandArora2011;Forgacsetal.2004;Haoetal.2000;Avlonitisetal.2008;Berberidouetal.2009;Harrelkasetal.2009;Zhaoetal.2009).Unfortunately,allthesemethodsarehighlycostlyandthuscommerciallyunattractive.Therefore,itismandatorytodevelopalternativemeansofdyedecolorization,suchasinnovativebiologicalmethods,toprovidemoreeconomicalcleanupprotocolsandallowtherecyclingofindustrialtreatedwastewaters.

Inrecentyears,bioremediationandmoregenerallybio-technologieshavegatheredgrowinginterestbecauseoftheircost-effectiveandeco-friendlyprofile(Khanetal.2013;Ali2010;Solísetal.2012).Somealgae(Daneshvaretal.2007;Khataeeetal.2010),bacteria(Ayedetal.2010;Amoozegaretal.2011;Sarataleetal.2011),fungi(KaushikandMalik2009;Novotnyetal.2011;Vermaetal.2012;Alietal.2008;Jinetal.2007;Xian-Chunetal.2007;FuandViraraghavan2001;Marimuthuetal.2013;Teglietal.2014),andyeasts(VitorandCorso2008;Quetal.2012)wereprovedtoachieveacceptableandefficientdyeremoval.Thevastmajorityoftheresearchonbiologicaldecolorizationhasbeencarriedoutonfungiandmainlyontheirligninolyticenzymes,discoveredtodegradeazodyesaerobically(Erkurtetal.2010).Conversely,studiesondyeremovaloperatedbybacteriaarerelativelylessreported(PokhariaandAhluwalia2013;SatheeshBabuetal.2013;Pandeyetal.2007),althoughthebacterialdecoloriza-tionisnormallyfasterthanthefungalsystems(ShobanaandThangam2012).Severalbacteriahavebeenshowntodegradeazodyes(Sarataleetal.2011),andithasbeendocumentedthatdecolorizationoccursviabacterialazoreductases,follow-edbytheaerobicmineralizationofcolorlessamines(Pandeyetal.2007;VanderZeeandVillaverde2005).Generally,thistwo-stepprocessmayrequireabacterialconsortiumtosuc-cessfullycompletetheazodyebiodegradationtask,butthereproducibilityprofileisoftenlowunderminingpotentialin-dustrialapplications(Phugareetal.2011).Themostexten-sivelystudiedbacterialspeciesbelongtothegenusPseudomonas(e.g.,P.luteola)(Changetal.2001;ChenandLin2007).Surprisingly,thedegradingabilitiesofentericbac-teriahavebeenbyfarlessinvestigated(Chenetal.2004;Mate

ApplMicrobiolBiotechnol

andPathade2012;Chanetal.2012)includingEscherichiacolifrequentlyusedtoproducerecombinantproteinsandoverexpressforeignbacterialgenescodingforazoreductaseenzymes(Lon?aretal.2013;Is?kandSponza2003;Sandhyaetal.2008;ChangandLin2001;Changetal.2000).

Inthispaper,weexploredforthefirsttimetheaerobicdyedegradingperformancesofE.coliDH5α,whosemetabolicpotentialindyebioremediationhasbeenrarelyexploredtothebestofourknowledge(Rauetal.2002).Thisstrainishighlyadaptable,ithastheaptitudetoswitchbetweenaerobicandanaerobiclifestyles(Douganetal.2001),anditischaracter-izedbyfastgrowthkineticevenonverysimplenutrientmedia(Sezonovetal.2007).E.coliDH5αwastestedonseveralazoandanthraquinonedyesamongthosemostcommonlyusedwithinthedyeingindustry.Thekineticsofdecolorizationandtheinfluenceofoperationalparameterswerealsostudiedonarepresentativedyeforeachchemicalgroup.Asignificantabi-oticdyeremovalwasalsorevealed,whichrarelyhasbeenconsideredinpreviousstudies(Sariogluetal.2007).

Materialsandmethods

Dyes

The15dyesusedinthisstudywerekindlyprovidedbyTintoriaCometaSrl(Prato,Italy)andwereofcommercialquality.Thesedyesweregroupedaccordingtotheirchemicalnature:acidanthraquinone(groupA),acidazo(groupB),basicanthraquinone(groupC),basicazo(groupD).Thename,CASnumber,andthewavelengthofmaximumabsorp-tion(λmax)ofeachdyearereportedinTable1.Experimentswerecarriedoutwithaninitialconcentrationof0.3mg/mlofeachdyedissolvedindoubledistilledwater.

E.coligrowthconditionsandculturemedia

ThebacterialstrainusedinthisstudywasE.coliDH5α(DSMNo.6897atLeibniz-InstituteDSMZ-GermanCollectionofMicroorganismsandCellCultures),grownaerobicallyat37°ConLuria–Bertanibroth(LB)(BDBiosciences,Milan,Italy,supplementedwith15mg/lofnalidixicacid(SigmaAldrichCo,Milan,Italy)),underorbitalshaking(150rpm).OvernightbacterialcultureshavinganOD600=1werehar-vestedbycentrifugation(5000g,10minatroomtemperature)andwashedtwicewithsterilephysiologicalsolution(NaCl8.5%w/winwater).Subsequently,thebacterialpelletswereusedfordecolorizationexperiments.TheaveragewetweightbiomassofE.coliculturesampledfromanearlystationaryphasewasapproximately1.0mg/ml,correspondingtoabout5×109cells/ml.

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