生化工程第三章固定化酶反應動力學

生化工程第三章固定化酶反應動力學第一頁，共三十六頁，編輯于2023年，星期三ImmobilizedEnzymeSystemsDefinitionTherestrictionofenzymemobilityinafixedspaceisknownasenzymeimmobilization.Ingeneral,immobilizedenzymesareenzymesthatareattachedto,orentrappedwithin,amacro-scopicsupportmatrixsothattheresultingcatalystcanbereused.TwooppositeconceptImmobilizedenzymeFreeenzyme第二頁，共三十六頁，編輯于2023年，星期三§3.1AdvantagesofImmobilizedEnzymesAdvantages:Enzymereutilization:catalystreuse;Eliminationofenzymerecoveryandpurificationprocesses:productpurity,whileeffluenthandlingproblems

;Provideabetterenvironmentforenzymeactivity;Disadvantages:Increasethediffusionresistance,sodecreasesthereactionrate.第三頁，共三十六頁，編輯于2023年，星期三§3.2ApplicationsofImmobilizedEnzymesImmobilizedenzymeareemployedinmanyfields.Analyticaldevices:Forexample:inimmobilizedenzymeelectrodesforthedetectionofvariouschemicalsubstances.Ascatalystinindustrialprocesses:Among2000typesofenzymesfound,only50~60havebeenappliedinindustry,mostofwhichareextracellularenzymes.第四頁，共三十六頁，編輯于2023年，星期三§3.3MethodsofImmobilizationImmobilizedSolubleEnzymesMembrane-EntrappedBetweenMacroscopicMembranesMicro-EncapsulatedCovalently-BoundToSupportToEnzymeEntrappedBoundAdsorbed(PhysicalorIonic)Matrix-Entrapped第五頁，共三十六頁，編輯于2023年，星期三Entrapment:Thephysicalenclosureofenzymesinasmallspace.Ploymericmaterials:Ca-alginate,agar,?-carrageenin, polyacrylamide,collagen;Solidmatrices:activatedcarbon,porousceramic, diatomaceousearth.MatrixentrapmentMatricesusedforenzymeimmobilizationareusually:Whenimmobilizedinapolymermatrix,enzymesolutionismixedwithpolymersolutionbeforepolymerizationtakesplace.第六頁，共三十六頁，編輯于2023年，星期三MembraneentrapmentMembrane:nylon,cellulose,polysulfone,polyacrylate.

Inallcases,asemi-permeablemembrane isusedtoretainhigh-MWcompounds(enzyme)whileallowingsmall-MWcompounds(substratesorproducts)accesstotheenzyme.Inthistechnique,microscopichollowspheresareformed.Thespherescontaintheenzymesolution,whilethesphereisenclosedwithaporousmembrane.Microencapsulation:aspecialformofmem-braneentrapment.第七頁，共三十六頁，編輯于2023年，星期三Problems:Leakageofenzymesintosolution:Considerablediffusionalresistanceemerges:Reducingtheparticlesizeofthematricesand/orcapsules;Reductionofenzymeactivityandstability:Alittledifficulttohandle.Lackofcontrolofthemicroenvironment:Altertheunfavorablemicroenvironmentalconditions;ReducingtheMWcutoffofmembranesortheporesizeofsolidmatrices;第八頁，共三十六頁，編輯于2023年，星期三Bound:Inorganicmaterials:alumina,silica,porousglass, ceramics,diatomaceousearth;Organicmaterials:cellulose(CMC,DEAE-cellulose), starch,activatedcarbon,ion- exchangeresin(Amberlite, Sephadex,Dowex).AdsorptionAphysicalattachmentofenzymeonthesurfacesofsupportparticlesbyweakphysicalforces:vanderWaals.Supportmaterials:第九頁，共三十六頁，編輯于2023年，星期三Desorptionisquitcommonbecausethebindingforcesaresoweek,especiallyinthepresenceofstronghydrodynamicforces.Advantages:Normally,activesiteisnotaffected,nearlyallactivityisretainedafterimmobilization.Disadvantages:第十頁，共三十六頁，編輯于2023年，星期三CovalentBindingItistheretentionofenzymesonsupportsurfacesbycovalentbondformation,viacertainfunctionalgroups,suchasamino,carboxyl,hydroxyl,and–SHgroup.Thefunctionalgroupsmustnotbetheactivesites.Cross-LinkingTheenzymemoleculescanalsocross-linkwitheachother.Butthismaycausesignificantchangesintheactivesiteofenzymes,andalsoseverediffusionlimitationsmayresult.第十一頁，共三十六頁，編輯于2023年，星期三SUMMARYThemostsuitablesupportmaterialandimmobilizationmethodvarydependingontheenzymeandparticularapplication.Thenhowtoselectsupportmaterials?Bindingcapacity,whichisafunctionofchargedensity,functionalgroups,porosity,andhydrophobicity;Stabilityandretentionoftheenzymeactivity,whichisafunctionoffunctionalgroupsonsupportmaterialandmicroenvironmentalconditions.第十二頁，共三十六頁，編輯于2023年，星期三Howtoselectmethodofimmobilization?第十三頁，共三十六頁，編輯于2023年，星期三CharacteristicCarrierBindingMethodsCross-linkingMethodEntrappingMethodPhysicaladsorptionIonicBindingCovalentBindingPreparationEasyEasyDifficultDifficultDifficultEnzymeActivityLowHighHighModerateHighSubstrateSpecificityUnchangeableUnchangeableChangeableChangeableUnchangeableBindingForceWeakModerateStrongStrongStrongRegenerationPossiblePossibleImpossibleImpossibleImpossibleGeneralApplicationLowModerateModerateLowHighCostofImmobilizationLowLowHighModerateLowTable:ComparisonoftheCharacteristicsofDifferentMethodsofEnzymeImmobilization第十四頁，共三十六頁，編輯于2023年，星期三§3.4ImmobilizedEnzymeKineticsBioreactorkineticsIntrinsickinetics(本征反應動力學)Masstransferofsubstrateandproduct第十五頁，共三十六頁，編輯于2023年，星期三IllustrationofMassTransportandChemicalReactionInteractionsinaSymmetricSlabofImmobilizedEnzyme.PHENOMENAPARAMETERSBulkFluidStagnantFilmorBoundaryLayerImmobilizedEnzymeSlabSurfaceofimmobilizedenzymeBulksolutionMasstransfercoefficient(kS,kP)Effectivediffusioncoefficient(DES,DEP)CONCENTRATIONPROFILECatalystthickness2LSubstratediffusionintopermeablecatalyst第十六頁，共三十六頁，編輯于2023年，星期三3.4.1DiffusionEffectsinSurface-BoundEnzymesonNonporousSupportMaterialsNon-porousSolidSupportFilmthicknessThefluxmass-transferrateJS

(mol/L·s)ofthesubstratefromthebulkfluidtotheinterface,Atsteadystate,thesubstratecannotaccumulateatthecatalystinterface,DefinetheDamkohlernumber:[Ss][Sb]bulksubstrateconcentration[SS]substrateconcentrationatsurfaceLiquidvolumetrictransfercoefficient第十七頁，共三十六頁，編輯于2023年，星期三Discussions:WhenDa?1,thesystemisstronglymasstransferlimited,Thesystembehaveasapseudo-firstorder.WhenDa?1,thesystemisreactionlimited,SbJSorvJSvR第十八頁，共三十六頁，編輯于2023年，星期三WhenDa≈1,wedefinethefollowingdimensionlessvariables,then,fromeq.Wecaneasilysolveout,第十九頁，共三十六頁，編輯于2023年，星期三Formoregeneralcases,namely,thediffusionresistanceandthereactionratearecomparable,analyticalsolutioncannoteasilybesolvedout,soweonlyhavetoturntosolvedgraphicallyorfindnumericalsolutions.Atlast,withthesubstrateconcentrationatsurface(SS),wecansolveoutthemacroscopicreactionratebymass-transferequationorintrinsickineticequation(本征動力學方程).第二十頁，共三十六頁，編輯于2023年，星期三SSJSorvvSlope=kLaJSSolutionforSbGraphicalsolutionforreactionrateforenzymeimmobilizedonanonporouscatalyst第二十一頁，共三十六頁，編輯于2023年，星期三例3-1某酶固定在無微孔球形基質(zhì)上，其本征動力學參數(shù)為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應速率？解題思路：這是一個外擴散限制下的固定化酶動力學問題，當體系達到平衡時，外擴散速率與球體表面上的本征反應速率一致，因此，將已知條件代入得：變換為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)第二十二頁，共三十六頁，編輯于2023年，星期三3.4.2DiffusionEffectsinEnzymesimmobilizedinAPorousMatrixTheenzymesareimmobilizedinapermeablecatalyticpellet.Thesubstratediffusesthroughthetortuouspathwayamongporesandreactswithenzymeimmobilizedonporesurface.Bulkandsurfaceconcentrationarethesame,assumingenzymeisimmobilizedwithapelletthathasapproximatelysphericalshape.第二十三頁，共三十六頁，編輯于2023年，星期三(I).ConcentrationdistributioninAPorousMatrixrr+ΔrRFick’smassdiffusionlawWhere,JSismassdiffusionrateofsubstrate, DeiseffectivediffusivityofsubstratewithintheporousmatrixMassdiffusion第二十四頁，共三十六頁，編輯于2023年，星期三MassBalancefor

TheShellAccumulationinsidethevolumeAmountenterthevolumeAmountexitthevolumeConsumedinsidethevolume=--AtsteadystateRearrange,rr+ΔrR第二十五頁，共三十六頁，編輯于2023年，星期三TakelimitasΔr→0Also,fortheM-Mmodel,Rearrange,第二十六頁，共三十六頁，編輯于2023年，星期三Withboundaryconditions:LetwhereφiscalledThielemodulus.Thenthepreviousdifferentialequationcanbewrittenaswithdimensionlessboundaryconditions:第二十七頁，共三十六頁，編輯于2023年，星期三Solutions:Thereactionrateisnotaffectedbythesubstrateconcentration:Let,Integrationgives,whereC1andC2areintegrationconstants.Zero-orderreactionrate,when第二十八頁，共三十六頁，編輯于2023年，星期三WhenS=0,wecangetthecriticalradius,Namely,Withtheboundaryconditionswecansolveout,第二十九頁，共三十六頁，編輯于2023年，星期三First-orderreactionrate,whenwhereφ1iscalledThielemodulus.第三十頁，共三十六頁，編輯于2023年，星期三(II).ThielemodulusForaspherical

porousmatrix,first-orderreactionrate,DefinitionofThielemodulusIt’sameasureoftheextentofinternaldiffusionresistancesThielemoduluscalculation第三十一頁，共三十六頁，編輯于2023年，星期三Wheninternaldiffusionlimitstheenzymaticreactionrate,therateconstantandvaluesarenottrueintrinsicrateconstants,butapparentones.Toobtaintrueintr