生物表面活性剂课件

Biosurfactant

姓名：吕梅玲

学号：SY1227111导师：江雷Introduction

Biosurfactants(amphiphiliccompounds)(synthesizedbymicroorganisms)hydrophobic(nonpolar)hydrophilic(polar)thatconferabilitytoaccumulatebetweenfluidphasessuchasoil/waterorair/water,reducingthesurfaceandinterfacialtensionsandformingemulsions.household、industryandagriculturemono-,oligo-orpolysaccharides(多糖）,peptides（缩氨酸）orproteinssaturated,unsaturatedandhydroxylatedfattyacidsorfattyalcoholsPseudomonasaeruginosa（绿脓假单胞菌）Acinetobactercalcoaceticus（醋酸钙不动杆菌）emulsan（乳化剂）Candidabombicola（假丝酵母菌）sophorolipids（槐糖脂）(Originally)hydrocarbonsdissolutionagentsfood,pharmaceuticalandoilindustry(recently)applicationenvironmentalfriendlyeasilybiodegradablelowtoxicityuniquestructuresRhamnolipids(鼠李糖脂）

Oneofthe

best-studiedglycolipidsisrhamnolipid,producedbyseveralspeciesofP.seudomonads（假单胞菌）,whichconsistsoftwomolesofrhamnoseandtwomolesofβ-hydroxydecanoicacid.

Thelowmolecularweightbiosurfactantsaregenerallyglycolipidsinwhichcarbohydratesareattachedtoalong-chainaliphaticacid(脂肪酸）orlipopeptides（脂肽）.Glycolipidbioemulsifiers,suchasrhamnolipids（鼠李糖脂）,trehaloselipids（海藻糖脂）andsophorolipids（槐糖脂）,aredisaccharides（二糖）thatareacylatedwithlong-chainfattyacidsorhydroxyfattyacids.Thehighmolecularweightsurfactantsarelesseffectiveinreducinginterfacialtension,butareefficientatcoatingtheoildropletsandpreventingtheircoalescence.Thesearehighlyefficientemulsifiersthatworkatlowconcentrations(0.01%–0.001%),representingemulsifier-to-hydrocarbonratiosof1:100–1:1000.

Thehighmolecularweightbacterialsurfactantsareproducedbyalargenumberofbacterialspeciesfromdifferentgeneraandarecomposedofpolysaccharides（多糖）,proteins,lipopolysaccharides（脂多糖）,lipoproteins（脂蛋白）orcomplexmixturesofthesebiopolymers.

otherscanalsoemulsifypurehydrocarbonsbutonlyofahighmolecularweight.Thebest-studiedbiosurfactantsarethebioemulsansproducedbydifferentspeciesofAcinetobacter.

Thesehighmolecularweightbioemulsifiersexhibitconsiderablesubstratespecificity.

Forexample,someemulsifyefficientlymixturesofaliphaticandaromatic(orcyclicalkane)hydrocarbons,butwillnotemulsifypurealiphatic,aromaticorcyclichydrocarbons;Basedonthemicrobialorigin,themajorclassofbiosurfactantinclude:Glycolipids(糖脂）˗Rhamnolipids（鼠李糖脂）˗Trehalolipids(海藻糖脂）˗Sophorolipids（槐糖脂）LipopeptideandLipoprotein（脂肽和脂蛋白）FattyAcids,Phospholipids（磷脂质),andNeutralLipidsPolymericBiosurfactantsParticulateBiosurfactantSurfaceandinterfaceactivity

Ingeneral,biosurfactantsaremoreeffectiveandefficientandtheirCMC(criticalmicelleconcentration)isabout10-40timeslowerthanchemicalsurfactants,i.e.,lesssurfactantisnecessarytogetamaximaldecreaseonST.

Agoodsurfactantcanlowersurfacetension(ST)ofwaterfrom72to35mN/mandtheinterfacialtension(IT)water/hexadecane（十六烷）from40to1mN/m.Thebiosurfactantsaccumulateattheinterfacebetweentwoimmisciblefluidsorbetweenafluidandasolid..(figure1)Byreducingsurface(liquid-air)andinterfacial(liquid-liquid)tensiontheyreducetherepulsiveforcesbetweentwodissimilarphasesandallowthesetwophasestomixandinteractmoreeasily

Thebiosurfactanteffectivenessisdeterminedbymeasuringitsabilitytochangesurfaceandinterfacialtensions,stabilizationofemulsionsandbystudyingitshydrophilic-lipophilicbalance(HLB).EmulsifierswithlowHLBarelipophilicandstabilizewater-in-oilemulsification,whereasemulsifierswithhighHLBhavetheoppositeeffectandconferbetterwatersolubilityLowtoxicity

Forexample:AbiosurfactantfromP.aeruginosa（绿脓假单胞菌）（wascomparedwithasyntheticsurfactant(MarlonA-350)widelyusedinindustryintermsoftoxicityandmutagenicproperties.Bothassaysindicatedthehighertoxicityandmutageniceffectofthechemical-derivedsurfactantwhereasbiosurfactantwasconsideredslightlytonon-toxicandnon-mutagenic.lowornon-toxicproductsandtherefore,appropriateforpharmaceutical,cosmeticandfooduses.Emulsionformingandemulsionbreaking

Anemulsionisaheterogeneoussystem,consistingofatleastoneimmiscibleliquidintimatelydispersedinanotherintheformofdroplets,whosediameteringeneralexceeds0.1µm.Emulsionshaveaninternalordispersedandanexternalorcontinuousphase,sotherearegenerallytwotypes:oil-in-water(o/w)orwater-in-oil(w/o)emulsions.

Suchsystemspossessaminimalstability,whichmaybeaccentuatedbyadditivessuchassurface-activeagents(surfactants).Thus,stableemulsionscanbeproducedwithalifespanofmonthsandyears.Biosurfactantsmaystabilize(emulsifiers)ordestabilize(de-emulsifiers)theemulsion.High-molecular-massbiosurfactantsareingeneralbetteremulsifiersthanlow-molecular-massbiosurfactants.Production

Biosurfactantsdonotcompeteeconomicallywithsyntheticsurfactants.Toreduceproductioncosts,othercarbonsources,suchasoliveoil（橄榄油），milleffluent（工厂废水）,whey（乳清）fromcheesemaking,andcassavaflourwater（木薯粉水）,usedvegetableoils,molasses（糖浆）(by-product).

Biosurfactantshavebeensynthesizedbyvariousresearchersusingdifferentmicroorganismsandcarbonsources.Thecarbonsourcesusedforbiosurfactantproductionarehydrocarbons,

carbohydrates,andvegetableoils.ProductionmethodsNaturalbiologicalextractmethod、Microorganismfermentationmethod、EnzymecatalyticmethodPurificationmethodsPrecipitationmethod、Extractionmethod、Superfilteringmethod、Foamseparationmethod、Adsorptionmethod、Columnchromatographymethod、Thinlayerchromatographymethod、Highperformanceliquidchromatographymethod、Liquidsurfaceadsorptionenrichmentmethod、Liquidmembraneseparationmethod.Fig.2.Structureoffourdifferentrhamnolipidsproducedby

P.aeruginosa.FactorsAffectingBiosurfactant

ProductionEffectofCarbonSourceonBiosurfactantsProduction

carbohydratehydrocarbonvegetableoilsEffectofSupportMaterialandRelationshipwithWater

Supportmaterialforimmobilizedenzymeaffectsthe

watercontentintheproximityoftheenzymeandthe

partitioningofreactantsand/orproductsinthereaction

mixture.Sincethermalstabilityiscloselyrelatedtothe

amountofwaterinclosevicinityoftheenzymesmolecule.Theidealcarriershouldnotretainwaterthan

necessarytoreducetheriskofenzymedenaturation（变性）.

Immobilizationonhydrophilicsupportsoftenleads

toalossoflipase（脂肪酶）activityastheenzymeundergoesa

conformational（构象）changetoaformofreducedactivity.

Thesesupportmaterialsmayalsoreducehydrophobic

substratesolubilityinhydrophilicregions,thereby

reducingthe

accessibilityofsubstratetotheactivesites.EffectofEnvironmentalFactorsonBiosurfactantsProduction

pHtemperatureagitation（搅拌）speedoxygenavailabilityRhamnolipidproductioninpseudomonassp（假单胞菌）wasitsmaximumatapHrangefrom

6to

6.5and

decreasedsharplyabovepH7.

Inaddition,surfacetensionandCMCsofabiosurfactantproduct

remainedstableoverawiderangeofpHvalues,whereasemulsificationhadanarrowerpHrange.amodifieddrop-collapsetechniqueforsurfactantquantitationandscreeningofbiosurfactantproducingmicroorganismsQualitativedrop-collapsetestAdropofwaterappliedtoahydrophobicsurfaceintheabsenceofsurfactantswillformabead,asshowninFig.1(A).Thebeadforms

becausethepolarwatermoleculesarerepelledfromthehydrophobicsurface.Incontrast,ifthewaterdropletcontainssurfactant,theforceorinterfacialtensionbetweenthewaterdropandthehydrophobicsurfaceisreduced,whichresultsinthespreadingofthewaterdropoverthehydrophobicsurface(Fig.1,B).Theamountofsurfactantrequiredtocausedrop-collapseisdependentontheabilityofthesurfactanttoreducesurfaceandinterfacialtension.Themorepotentthesurfactant,thesmallerthequantitythatcanbedetected.

(A)Watercontrol(nosurfactant),(B)1000mg/Lrhamnolipid.surfactantquantitationbythedrop-collapseQuantitativedrop-collapsemethod:(A)Watercontrol,(B)25mg/Lrhamnolipid,(C)50mg/Lrhamnolipid,(D)75mg/Lrhamnolipidand(E)100mg/Lrhamnolipid.Inthiscase,asthesurfactantconcentrationincreased,thediameterofthesampledropincreased.BiosurfactantsinMicrobialEnhancedOilRecovery(MEOR)

Fig.Mechanismofenhancedoilrecoverybybiosurfactants.theoilistrappedintheporesbycapillary

pressure.

Biosurfactantsreduceinterfacialtensionbetweenoil/waterandoil/rock.Thisreducesthecapillaryforcespreventingoilfrommovingthroughrockpores.Biosurfactantscanalsobindtightlytotheoil-waterinterfaceandformemulsion.Thisstabilizesthedesorbedoilinwaterandallowsremovalofoil