生化工程第三章固定化酶反应动力学

生化工程第三章固定化酶反应动力学第1页，课件共36页，创作于2023年2月ImmobilizedEnzymeSystemsDefinitionTherestrictionofenzymemobilityinafixedspaceisknownasenzymeimmobilization.Ingeneral,immobilizedenzymesareenzymesthatareattachedto,orentrappedwithin,amacro-scopicsupportmatrixsothattheresultingcatalystcanbereused.TwooppositeconceptImmobilizedenzymeFreeenzyme第2页，课件共36页，创作于2023年2月§3.1AdvantagesofImmobilizedEnzymesAdvantages:Enzymereutilization:catalystreuse;Eliminationofenzymerecoveryandpurificationprocesses:productpurity,whileeffluenthandlingproblems

;Provideabetterenvironmentforenzymeactivity;Disadvantages:Increasethediffusionresistance,sodecreasesthereactionrate.第3页，课件共36页，创作于2023年2月§3.2ApplicationsofImmobilizedEnzymesImmobilizedenzymeareemployedinmanyfields.Analyticaldevices:Forexample:inimmobilizedenzymeelectrodesforthedetectionofvariouschemicalsubstances.Ascatalystinindustrialprocesses:Among2000typesofenzymesfound,only50~60havebeenappliedinindustry,mostofwhichareextracellularenzymes.第4页，课件共36页，创作于2023年2月§3.3MethodsofImmobilizationImmobilizedSolubleEnzymesMembrane-EntrappedBetweenMacroscopicMembranesMicro-EncapsulatedCovalently-BoundToSupportToEnzymeEntrappedBoundAdsorbed(PhysicalorIonic)Matrix-Entrapped第5页，课件共36页，创作于2023年2月Entrapment:Thephysicalenclosureofenzymesinasmallspace.Ploymericmaterials:Ca-alginate,agar,ĸ-carrageenin, polyacrylamide,collagen;Solidmatrices:activatedcarbon,porousceramic, diatomaceousearth.MatrixentrapmentMatricesusedforenzymeimmobilizationareusually:Whenimmobilizedinapolymermatrix,enzymesolutionismixedwithpolymersolutionbeforepolymerizationtakesplace.第6页，课件共36页，创作于2023年2月MembraneentrapmentMembrane:nylon,cellulose,polysulfone,polyacrylate.

Inallcases,asemi-permeablemembrane isusedtoretainhigh-MWcompounds(enzyme)whileallowingsmall-MWcompounds(substratesorproducts)accesstotheenzyme.Inthistechnique,microscopichollowspheresareformed.Thespherescontaintheenzymesolution,whilethesphereisenclosedwithaporousmembrane.Microencapsulation:aspecialformofmem-braneentrapment.第7页，课件共36页，创作于2023年2月Problems:Leakageofenzymesintosolution:Considerablediffusionalresistanceemerges:Reducingtheparticlesizeofthematricesand/orcapsules;Reductionofenzymeactivityandstability:Alittledifficulttohandle.Lackofcontrolofthemicroenvironment:Altertheunfavorablemicroenvironmentalconditions;ReducingtheMWcutoffofmembranesortheporesizeofsolidmatrices;第8页，课件共36页，创作于2023年2月Bound:Inorganicmaterials:alumina,silica,porousglass, ceramics,diatomaceousearth;Organicmaterials:cellulose(CMC,DEAE-cellulose), starch,activatedcarbon,ion- exchangeresin(Amberlite, Sephadex,Dowex).AdsorptionAphysicalattachmentofenzymeonthesurfacesofsupportparticlesbyweakphysicalforces:vanderWaals.Supportmaterials:第9页，课件共36页，创作于2023年2月Desorptionisquitcommonbecausethebindingforcesaresoweek,especiallyinthepresenceofstronghydrodynamicforces.Advantages:Normally,activesiteisnotaffected,nearlyallactivityisretainedafterimmobilization.Disadvantages:第10页，课件共36页，创作于2023年2月CovalentBindingItistheretentionofenzymesonsupportsurfacesbycovalentbondformation,viacertainfunctionalgroups,suchasamino,carboxyl,hydroxyl,and–SHgroup.Thefunctionalgroupsmustnotbetheactivesites.Cross-LinkingTheenzymemoleculescanalsocross-linkwitheachother.Butthismaycausesignificantchangesintheactivesiteofenzymes,andalsoseverediffusionlimitationsmayresult.第11页，课件共36页，创作于2023年2月SUMMARYThemostsuitablesupportmaterialandimmobilizationmethodvarydependingontheenzymeandparticularapplication.Thenhowtoselectsupportmaterials?Bindingcapacity,whichisafunctionofchargedensity,functionalgroups,porosity,andhydrophobicity;Stabilityandretentionoftheenzymeactivity,whichisafunctionoffunctionalgroupsonsupportmaterialandmicroenvironmentalconditions.第12页，课件共36页，创作于2023年2月Howtoselectmethodofimmobilization?第13页，课件共36页，创作于2023年2月CharacteristicCarrierBindingMethodsCross-linkingMethodEntrappingMethodPhysicaladsorptionIonicBindingCovalentBindingPreparationEasyEasyDifficultDifficultDifficultEnzymeActivityLowHighHighModerateHighSubstrateSpecificityUnchangeableUnchangeableChangeableChangeableUnchangeableBindingForceWeakModerateStrongStrongStrongRegenerationPossiblePossibleImpossibleImpossibleImpossibleGeneralApplicationLowModerateModerateLowHighCostofImmobilizationLowLowHighModerateLowTable:ComparisonoftheCharacteristicsofDifferentMethodsofEnzymeImmobilization第14页，课件共36页，创作于2023年2月§3.4ImmobilizedEnzymeKineticsBioreactorkineticsIntrinsickinetics(本征反应动力学)Masstransferofsubstrateandproduct第15页，课件共36页，创作于2023年2月IllustrationofMassTransportandChemicalReactionInteractionsinaSymmetricSlabofImmobilizedEnzyme.PHENOMENAPARAMETERSBulkFluidStagnantFilmorBoundaryLayerImmobilizedEnzymeSlabSurfaceofimmobilizedenzymeBulksolutionMasstransfercoefficient(kS,kP)Effectivediffusioncoefficient(DES,DEP)CONCENTRATIONPROFILECatalystthickness2LSubstratediffusionintopermeablecatalyst第16页，课件共36页，创作于2023年2月3.4.1DiffusionEffectsinSurface-BoundEnzymesonNonporousSupportMaterialsNon-porousSolidSupportFilmthicknessThefluxmass-transferrateJS

(mol/L·s)ofthesubstratefromthebulkfluidtotheinterface,Atsteadystate,thesubstratecannotaccumulateatthecatalystinterface,DefinetheDamkohlernumber:[Ss][Sb]bulksubstrateconcentration[SS]substrateconcentrationatsurfaceLiquidvolumetrictransfercoefficient第17页，课件共36页，创作于2023年2月Discussions:WhenDa»1,thesystemisstronglymasstransferlimited,Thesystembehaveasapseudo-firstorder.WhenDa«1,thesystemisreactionlimited,SbJSorvJSvR第18页，课件共36页，创作于2023年2月WhenDa≈1,wedefinethefollowingdimensionlessvariables,then,fromeq.Wecaneasilysolveout,第19页，课件共36页，创作于2023年2月Formoregeneralcases,namely,thediffusionresistanceandthereactionratearecomparable,analyticalsolutioncannoteasilybesolvedout,soweonlyhavetoturntosolvedgraphicallyorfindnumericalsolutions.Atlast,withthesubstrateconcentrationatsurface(SS),wecansolveoutthemacroscopicreactionratebymass-transferequationorintrinsickineticequation(本征动力学方程).第20页，课件共36页，创作于2023年2月SSJSorvvSlope=kLaJSSolutionforSbGraphicalsolutionforreactionrateforenzymeimmobilizedonanonporouscatalyst第21页，课件共36页，创作于2023年2月例3-1某酶固定在无微孔球形基质上，其本征动力学参数为Vmax=4X10-5mol/(LS),Km=2X10-5mol/L.[Sb]=1X10-5mol/L,kLa=0.4s-1,求[SS]和底物在固定化酶外表面上的反应速率？解题思路：这是一个外扩散限制下的固定化酶动力学问题，当体系达到平衡时，外扩散速率与球体表面上的本征反应速率一致，因此，将已知条件代入得：变换为一元二次方程后求解得：[SS]=0.18x10-5mol/L所以vsurface=kLax([Sb]-[SS])=0.4x(1-0.18)x10-5 =0.328x10-5mol/(Ls)第22页，课件共36页，创作于2023年2月3.4.2DiffusionEffectsinEnzymesimmobilizedinAPorousMatrixTheenzymesareimmobilizedinapermeablecatalyticpellet.Thesubstratediffusesthroughthetortuouspathwayamongporesandreactswithenzymeimmobilizedonporesurface.Bulkandsurfaceconcentrationarethesame,assumingenzymeisimmobilizedwithapelletthathasapproximatelysphericalshape.第23页，课件共36页，创作于2023年2月(I).ConcentrationdistributioninAPorousMatrixrr+ΔrRFick’smassdiffusionlawWhere,JSismassdiffusionrateofsubstrate, DeiseffectivediffusivityofsubstratewithintheporousmatrixMassdiffusion第24页，课件共36页，创作于2023年2月MassBalancefor

TheShellAccumulationinsidethevolumeAmountenterthevolumeAmountexitthevolumeConsumedinsidethevolume=--AtsteadystateRearrange,rr+ΔrR第25页，课件共36页，创作于2023年2月TakelimitasΔr→0Also,fortheM-Mmodel,Rearrange,第26页，课件共36页，创作于2023年2月Withboundaryconditions:LetwhereφiscalledThielemodulus.Thenthepreviousdifferentialequationcanbewrittenaswithdimensionlessboundaryconditions:第27页，课件共36页，创作于2023年2月Solutions:Thereactionrateisnotaffectedbythesubstrateconcentration:Let,Integrationgives,whereC1andC2areintegrationconstants.Zero-orderreactionrate,when第28页，课件共36页，创作于2023年2月WhenS=0,wecangetthecriticalradius,Namely,Withtheboundaryconditionswecansolveout,第29页，课件共36页，创作于2023年2月First-orderreactionrate,whenwhereφ1iscalledThielemodulus.第30页，课件共36页，创作于2023年2月(II).ThielemodulusForaspherical

porousmatrix,first-orderreactionrate,DefinitionofThielemodulusIt’sameasureoftheextentofinternaldiffusionresistancesThielemoduluscalculation第31页，课件共36页，创作于2023年2月Wheninternaldiffusionlimitstheenzymaticreactionrate,therateconstantandvaluesarenottrueintrinsicrateconstants,butapparentones.Toobtaintrue