生化工程,第三章固定化酶反应动力学PPT演示课件

生化工程,第三章固定化酶反应动力学,1,ImmobilizedEnzymeSystems,Definition,Therestrictionofenzymemobilityinafixedspaceisknownasenzymeimmobilization.Ingeneral,immobilizedenzymesareenzymesthatareattachedto,orentrappedwithin,amacro-scopicsupportmatrixsothattheresultingcatalystcanbereused.,2,3.1AdvantagesofImmobilizedEnzymes,Advantages:,Enzymereutilization:catalystreuse;,Eliminationofenzymerecoveryandpurificationprocesses:productpurity,whileeffluenthandlingproblems;,Provideabetterenvironmentforenzymeactivity;,Disadvantages:,Increasethediffusionresistance,sodecreasesthereactionrate.,3,3.2ApplicationsofImmobilizedEnzymes,Immobilizedenzymeareemployedinmanyfields.,4,3.3MethodsofImmobilization,ImmobilizedSolubleEnzymes,5,Entrapment:,Thephysicalenclosureofenzymesinasmallspace.,Whenimmobilizedinapolymermatrix,enzymesolutionismixedwithpolymersolutionbeforepolymerizationtakesplace.,6,Membraneentrapment,Membrane:nylon,cellulose,polysulfone,polyacrylate.,Inallcases,asemi-permeablemembraneisusedtoretainhigh-MWcompounds(enzyme)whileallowingsmall-MWcompounds(substratesorproducts)accesstotheenzyme.,Inthistechnique,microscopichollowspheresareformed.Thespherescontaintheenzymesolution,whilethesphereisenclosedwithaporousmembrane.,Microencapsulation:aspecialformofmem-braneentrapment.,7,Problems:,Leakageofenzymesintosolution:,Considerablediffusionalresistanceemerges:,Reducingtheparticlesizeofthematricesand/orcapsules;,Reductionofenzymeactivityandstability:,Alittledifficulttohandle.,Lackofcontrolofthemicroenvironment:,Altertheunfavorablemicroenvironmentalconditions;,ReducingtheMWcutoffofmembranesortheporesizeofsolidmatrices;,8,Bound:,Supportmaterials:,9,10,CovalentBinding,Itistheretentionofenzymesonsupportsurfacesbycovalentbondformation,viacertainfunctionalgroups,suchasamino,carboxyl,hydroxyl,andSHgroup.,Thefunctionalgroupsmustnotbetheactivesites.,11,SUMMARY,Themostsuitablesupportmaterialandimmobilizationmethodvarydependingontheenzymeandparticularapplication.,Thenhowtoselectsupportmaterials?,Bindingcapacity,whichisafunctionofchargedensity,functionalgroups,porosity,andhydrophobicity;,Stabilityandretentionoftheenzymeactivity,whichisafunctionoffunctionalgroupsonsupportmaterialandmicroenvironmentalconditions.,12,Howtoselectmethodofimmobilization?,13,Table:ComparisonoftheCharacteristicsofDifferentMethodsofEnzymeImmobilization,14,3.4ImmobilizedEnzymeKinetics,Intrinsickinetics(本征反应动力学),Masstransferofsubstrateandproduct,15,IllustrationofMassTransportandChemicalReactionInteractionsinaSymmetricSlabofImmobilizedEnzyme.,PHENOMENA,PARAMETERS,CONCENTRATIONPROFILE,16,3.4.1DiffusionEffectsinSurface-BoundEnzymesonNonporousSupportMaterials,Non-porousSolidSupport,Filmthickness,Thefluxmass-transferrateJS(mol/Ls)ofthesubstratefromthebulkfluidtotheinterface,Atsteadystate,thesubstratecannotaccumulateatthecatalystinterface,DefinetheDamkohlernumber:,Ss,SbbulksubstrateconcentrationSSsubstrateconcentrationatsurface,Liquidvolumetrictransfercoefficient,17,Discussions:,WhenDa1,thesystemisstronglymasstransferlimited,Thesystembehaveasapseudo-firstorder.,WhenDa1,thesystemisreactionlimited,Sb,JSorv,JS,v,R,18,WhenDa1,wedefinethefollowingdimensionlessvariables,then,fromeq.,Wecaneasilysolveout,19,Formoregeneralcases,namely,thediffusionresistanceandthereactionratearecomparable,analyticalsolutioncannoteasilybesolvedout,soweonlyhavetoturntosolvedgraphicallyorfindnumericalsolutions.,Atlast,withthesubstrateconcentrationatsurface(SS),wecansolveoutthemacroscopicreactionratebymass-transferequationorintrinsickineticequation(本征动力学方程).,20,Graphicalsolutionforreactionrateforenzymeimmobilizedonanonporouscatalyst,21,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),22,3.4.2DiffusionEffectsinEnzymesimmobilizedinAPorousMatrix,Theenzymesareimmobilizedinapermeablecatalyticpellet.Thesubstratediffusesthroughthetortuouspathwayamongporesandreactswithenzymeimmobilizedonporesurface.,Bulkandsurfaceconcentrationarethesame,assumingenzymeisimmobilizedwithapelletthathasapproximatelysphericalshape.,23,(I).ConcentrationdistributioninAPorousMatrix,Ficksmassdiffusionlaw,Where,JSismassdiffusionrateofsubstrate,Deiseffectivediffusivityofsubstratewithintheporousmatrix,Massdiffusion,24,MassBalanceforTheShell,Accumulationinsidethevolume,Amountenterthevolume,Amountexitthevolume,Consumedinsidethevolume,=,-,-,Atsteadystate,Rearrange,25,Takelimitasr0,Also,fortheM-Mmodel,Rearrange,26,Withboundaryconditions:,Let,whereiscalledThielemodulus.,Thenthepreviousdifferentialequationcanbewrittenas,withdimensionlessboundaryconditions:,27,Solutions:,Thereactionrateisnotaffectedbythesubstrateconcentration:,Let,Zero-orderreactionrate,when,28,WhenS=0,wecangetthecriticalradius,Namely,29,First-orderreactionrate,when,where1iscalledThielemodulus.,30,(II).Thielemodulus,Forasphericalporousmatrix,first-orderreactionrate,DefinitionofThielemodulus,Itsameasureoftheextentofinternaldiffusionresistances,Thielemoduluscalculation,31,Wheninternaldiffusionlimitstheenzymaticreactionrate,therateconstantandvaluesarenottrueintrinsicrateconstants,butapparentones.,Toobtaintrueintrinsicrateconstants,diffusionresistancesshouldbeeliminatedby:,32,Theeffectivenessfactorisdefinedastheratioof,Itsameasureoftheextentofdiffusionl