微波+酶,13

微波生物 淀粉酯

InternationalJournalofBiologicalMacromolecules39(2006)

265–272

Enzymaticesteri cationofstarchusingrecoveredcoconutoil

AkhilaRajan,V.S.Prasad,T.EmiliaAbraham

PolymerSection,ChemicalScienceDivision,RegionalResearchLaboratory(CSIR),Trivandrum695019,India

Received7March2006;receivedinrevisedform31March2006;accepted5April2006

Availableonline27April2006

Abstract

Modi cationofmaizeandcassavastarcheswasdoneusingrecoveredcoconutoilandmicrobiallipase.Microwaveesteri cationwasadvantageousasitgaveaDS1.55and1.1formaizestarchandcassavastarch,respectively.Solutionstateesteri cationofcassavastarchfor36hat60 CgaveaDSof0.08andsemi-solidstateesteri cationgaveaDSof0.43.TGAandDSCstudiesshowedthatthehigherDSattributedtothethermostability,sinceonsetofdecompositionisatahighertemperature(492 C)thantheunmodi ed(330 C)andwasstableabove600 C. -Amylasedigestibilityandviscosityreducedformodi edstarch.©2006PublishedbyElsevierB.V.

Keywords:Degreeofsubstitution;Recoveredcoconutoil;Lipase

1.Introduction

Modi edstarchesweredevelopedtoexpandtheusefulnessofstarchforamyriadofindustrialapplications.Starchshowsvariouschangesincharacteristicsaftermodifyingsuchassolu-bility,gelatinizationtemperature,viscosity,stabilityofthepaste,moisture,emulsi ability,waterretention,and lmproperty.Modi cationofthestarchOHgroupsbyesteri cationtoformappropriatedegreeofsubstitution(1.5–3.0DS)andwithhighpercentagedegreeofsubstitution(50–95%)impartsthermoplas-ticityandwaterresistancetothestarchesterovertheunmodi edstarch.Chemicalmodi cationofstarchisoftenrequiredtobettersuititspropertiestospeci capplication.Chemicalesteri cationofstarchisusuallydoneathighpH,usingharshchemicalslikeNaOH,pyridineandanhydridesandacidchloridesoftheacids.Esteri cationofstarchwithlongchainfattyacidsgivesther-moplasticstarches,whichhasgotwideuseinplasticindustryandpharmaceuticalindustry.Themainproblemhereistheincorporationofthefattyacidtothestarch,tobringabouttheesteri cation.Normally,DMSOisusedtosolubilizethestarchtomakeitmorereactivetowardsesteri cation.Starchesterswithlowdegreesofsubstitution(DS)havebeenpreparedinaqueousmediabybatchmethods[1].Extrudershavebeenused

Correspondingauthor.Tel.:+914712515253;fax:+914712490186.E-mailaddress:emiliatea@http://doc.xuehai.net(T.EmiliaAbraham).

aschemicalreactorsforpolymerizationofplastics[2]andgraftpolymerizationofplasticsontostarch[3].Extrudershavebeenusedtomanufacturecarboxylmethylatedandcationicpotatostarch[4],starchphosphate[5],anionicstarch(estersofvariousdicarboxylicacid)[6]andoxidizedstarches[7].Extruderscanhandleviscousliquidsandgellingofthestarchisnotaproblem.Biocatalysisisanenvironmentallyfriendlymethodandoccursundermilderconditions.Regiospeci candstereospe-ci cesteri cationcanbeeasilycarriedoutusingenzymes.Enzymeslikelipasesandproteaseshavebeenusedfortheesteri cationofsimplesugars.Theproductionprocessisenvi-ronmentalfriendlybecausenoby-productsaregenerated.

Modi cationofstarchwithlongchainfattyacidshasbiomed-icalapplicationssuchasmaterialsforbone xationandreplace-ments,carriersforcontrolledreleaseofdrugsandotherbioactiveagents[8].Theseincludestarch-basedbiomaterialsasscaffoldsforthetissueengineeringofboneandcartilage[9]materialsforbone xationandreplacementaswellasfor llingbonedefects[10–13].Theyareusedinmanybranchesofindustryasglues,adhesivesandauxiliariesofawiderangeofrheologicalandfunctionalproperties[14].

Microwaveesteri cationhasbeenusedforstarchesters[15]anddoesnotaffectmolecularweightdistributionandgranu-larstructureofmodi edstarchesascomparedtoproductsoftraditionaltechnology.Here,wehaveattemptedtoesterifythepregelatinizedstarchbyanenzyme(lipolase)usinghighshearmixinginaplasticorder,solutionstatereactioninahotwater

0141-8130/$–seefrontmatter©2006PublishedbyElsevierB.V.doi:10.1016/j.ijbiomac.2006.04.006

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