英文----经漆酶介体体系处理后黄麻纤维中木质素结构的影响

StructuralchangesoflignininthejutefibertreatedbylaccaseandmediatorsystemYongbingZhang,QiangWang*,XuerongFan,JiugangYuanKeyLaboratoryofScienceandTechnologyofEco-Textile,MinistryofEducation,JiangnanUniversity,Wuxi,Jiangsu214122,PRChina1AbstractTostudythestructuralchangesoflignininthejutefibertreatedwithlaccaseandmediatorsystem(LMS),ligninsfromthecontrolandLMS-treatedjutefiberwereisolatedandcharacterizedbygelpermeationchromatography(GPC),elementalanalysis,measurementofphenolichydroxylgroupcontent,FTIRand1HNMR.TheresultsshowedthatthemolecularweightsoftheligninfromLMS-treatedjutefiberwerelowerthanthoseoftheligninfromthecontroljutefiber.Thecontentsofphenolichydroxylgroup,aliphatichydroxylgroupandmethoxygroupoftheligninfromLMS-treatedjutefiberdecreased,whilethecontentofcarboxylgroupincreased.Keywords:laccase,jutefiber,lignin,degradation,mediator1.IntroductionThejutefiberligniniscomposedofp-hydroxyphenyl(H),guaiacyl(G)andsyringyl(S)unitswithaH/G/Scompositionof2:32:66andaS/Grationof2.1[1].Thelignincontentinjutefiberisuptoca.16%,whichresultedinthecoarsenessandrigidityofthefiber.Therefore,jutefibersaremainlyusedtomakethelow-gradegoodssuchaspackagefabricsandbags[2-3].Theremovalofligninfromjutefiberisprovedtobeakeystepinthemanufacturingofhigh-valuetextileproducts.Inthetraditionalprocess,theligninsinjutefibersareeliminatedmainlyin*Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail]alproducts,whichoftencausesevereenvironmentalpollution.Inordertoovercomethedisadvantagesofchemicaldegumming,enzymaticdegumminghasbeenattractedagreatdealofattention.Laccases(benzenediol:oxygenoxidoreductases,EC1.10.3.2)areawidespreadgroupofmulti-copperenzymes[4].Ithasbeenreportedbymanyresearchersthatlaccasecandegradeorpolymerizethephenoliccompoundsinlignin[5-6].Furthermore,whenlaccaseisusedinthepresenceofamediator,suchas2,2-azonabis(3-ethylbenzthiazoline-6sulfonate)(ABTS)[6],1-hydroxybenzotriazole(HOBT)[7]and2,2’,6,6’-tetramethyl-piperidine-N-oxyl(TEMPO)[8],itcanfurtherdegradethenonphenolicsubunitsoflignin.Themediatorshavehighredoxpotentialvaluesandcanproduceradicalswhichtransferelectronsfromlignintotheenzyme,whichfinallyreducesoxygentowater[9-11].Theuseofalaccase-mediatorsystem(LMS)isoneofthepromisingpossibilitiesasenvironmentallybenignprocessesforpulpbiobleaching[12-13],enzymaticpulping[14]andoldnewspaperdeinking[15]becauseofitsabilitytodelignify.Bio-degummingreferstotheenzymaticremovalofthenon-cellulosicmatterssuchaswaxes,pectinsandligninsfromthesurfaceofbastfiber,whichendowsthefiberwithbetterhydrophilicityinfavorofsubsequentprocesses.Laccaseisalsoapromisingenzymeforthedegummingofbastfiberstoremoveligninsbecauseofitsabilityofdelignification.Renetal.reportedthatthelignincontentoflinenfiberstreatedbylaccasewasdecreasedfrom4.4%to2.3%[16].Liuetal.investigatedthedegummingofjutefiberswithlaccaseandpectinase[17].Theyfoundthatthecomplexenzymeshowedbetterremovingeffectforlignin.Inourpreviouswork,thedegummingoflinen/cottonfabricwithpectinase,cellulose,xylanaseandlaccasewereinvestigated[18].Theresultsshowedthatlaccasetreatmentwasthebestwaytoremoveligninsfromlinen/cottonfabric,butitstillhadabiggapcomparedtothetraditionalprocess.Theseresultsindicatedthatdegummingofbastfiberswithlaccaseisafeasiblemethod.Nevertheless,themechanismofligninoxidationduringbastfiberdegummingwithLMSisnotwellestablished.DegummingofbastfiberswithLMSmaybeimprovedifthefundamentalchemicalreactionscontributingtothisprocessarewellunderstood.Inthisstudy,thejutefibersweretreatedbyLMS,andthentheligninswereextractedfromitwithdioxane/watersolution.ThestructurechangesofligninsfromthecontrolandLMS-treatedjutefiberswerecharacterizedbyGPC,elementalanalysis,FTIRand1HNMR.WehopetheresultswillprovideusefulreferencestothedegummingofjutefiberswithLMS.2.MaterialsandMethods2.1MaterialsJutefiberwassuppliedbyChangshuAocunLongtaiweavingCo.,Ltd.LaccasefromTrametesVersicolorwithanactivityof5.43U/mgwassuppliedbySigma.Oneunitoflaccaseactivitywasdefinedastheamountofenzymeconverting1μmoleofcatecholperminutein50mMsodiumcitratebuffer(pH6)at25oCusingcatecholassubstrate.2,2'-azinobis(3-ethylbenzthiazoline-6-sulphonate)(ABTS)providedbySigmawasusedasamediator.2.2TreatmentofthejutefiberswithLMSThereactionsolution(300mL)containedjutefibers(13g),laccase(totalactivity160U),ABTS(10mg),sodiumacetatebuffer(0.05M,pH6).Themixtureswereshakenandbubbledairat25oCfor6h.Aftertheenzymaticreaction,thejutefiberswerewashedseveraltimeswithwater,andair-dried.2.3IsolationofligninsfromthejutefibersThecorrespondingresidualligninsinthecontrolandLMS-treatedjutefibers,LcandLt,wereisolatedusingamethodasdescribedbyEvtuguinetal.withslightmodification[19].ThecontrolandLMS-treatedjutefibersweregroundto40meshfractions,refluxedwithethanol-benzene(1:2,v/v)solventfor6h,andthendriedatroomtemperature.Thesefractionswererefluxedwithdioxane-water(9:1,v/v)solutioncontaining0.2MHClat90oCfor60min.Theliquidphasewasdecantedafterthemixturewascooledtoroomtemperature.Thesolidresiduewassubjectedtoth