生物技术导论教案天津科技大学生活好文

1/1生物技术导论教案-天津科技大学-生活好文

生物技术导论教案-天津科技高校

生物技术导论教案

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生物技术导论教案-天津科技高校

生物技术导论（Introductiontobiotechnology）课程教案Topic:Chapter1Overviewofbiotechnology

Learningtargets：

1.Understandingthebasicconceptsofbiotechnology.

2.Knowingthepublicconceptionsofbiotechnology.

3.Understandingtheuseofbiotechnologyincommercialproduction.

Keyissues:biotechnology,geneticengineering,productsafety.

Difficultissues:applicationsofbiotechnology.

Teachingoutlineandtimedistribution:

1.1Introduction1.2Applicationsofbiotechnology

1.2.1Medicine1.2.2Agricultureandfood1.2.3Otherindustries1.3Publicperceptionofbiotechnology

1.4Productsafety

1.5ThefutureofbiotechnologyMethodology:

1.Describetheprincipleswithhelpofpracticalcases;

2.Showpicturesandphotos;

3.Askquestionsandsummarizing;

4.Multiplemediaandhandwriting;

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生物技术导论教案-天津科技高校

Chapter1Overviewofbiotechnology

1.1Introduction

Biotechnologyistechnologybasedonbiology,especiallywhenusedinagriculture,foodscience,medicine,andenvironment.UnitedNationsConventiononBiologicalDiversitydefinesbiotechnologyas:“Anytechnologicalapplicationthatusesbiologicalsystems,deadorganisms,orderivativesthereof,tomakeormodifyproductsorprocessesforspecificuse.”AndTheEuropeanFederationofBiotechnology(EFB)considersbiotechnologyas“theintegrationofnaturalsciencesandorganisms,cells,partsthereof,andmolecularanaloguesforproductsandservices.”

Insimplewordsbiotechnologyisanytechnologicalapplicationwhichisusedtomakeachangeinacellorinbiologicalsystem.Biotechnologydrawsonthepurebiologicalsciences(genetics,microbiology,cellbiology,molecularbiology,biochemistry)andinmanyinstancesisalsodependentonknowledgeandmethodsfromoutsidethesphereofbiology(physics,chemistry,mathematics).Conversely,modernbiologicalsciences(includingevenconceptssuchasmolecularecology)areintimatelydependentonthemethodsdevelopedthroughbiotechnology.

Historically,biotechnologyevolvedasanagriculturalskillratherthanascience.Throughearlybiotechnology,farmerswereabletousemicrobestoproducefoodsandbeverages,suchasbreadandbeer,andtomodifyplantsandanimalsthroughprogressiveselectionfordesiredtraits.

Thenewbiotechnologyrevolutionbeganinthe1970sandearly1980swhenscientistslearnedtoalterpreciselythegeneticconstitutionoflivingorganismsbyprocessesoutsideoftraditionalbreedingpractices.This‘geneticengineering’hashadaprofoundimpactonalmostallareasoftraditionalbiotechnologyandfurtherpermittedbreakthroughsinmedicineandagriculture,inparticular,thatwouldbeimpossiblebytraditionalbreedingapproaches.

Someofthemostexcitingadvanceswillbeinnewpharmaceuticaldrugsandtherapiestoimprovethetreatmentofmanydiseases,andintheproductionofhealthierfoods,selectivepesticidesandinnovativeenvironmentaltechnologies.

Sincethe1980sbiotechnologyhasbeenrecognizedandacceptedasastrategictechnologybymostindustrializednations.Revenueintheindustryovertheworldisexpectedtobemorethan130billionUSdollarsin2023,andtogrowby12.9%in2023.Theeconomicreturnsfrominvestinginstrategictechnologiesaccruenotjustto

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生物技术导论教案-天津科技高校

thecompaniesconductingresearchanddevelopment(RD)butmoreimportantlyreturnstosocietyoverallareestimatedtobeevenhigher.

Thepresentindustrialactivitiestobeaffectedmostwillincludehumanandanimalfoodproduction,provisionofchemicalfeedstockstoreplacepetrochemicalsources,alternativeenergysources,wasterecycling,pollutioncontrol,agriculture,aquacultureandforestry.

1.2Applicationsofbiotechnology

1.2.1Medicine

Mosttraditionalpharmaceuticaldrugsarerelativelysimplemoleculesthathavebeenfoundprimarilythroughtrialanderrortotreatthesymptomsofadiseaseorillness.Biopharmaceuticalsarelargebiologicalmoleculesknownasproteinsandtheseusuallytargettheunderlyingmechanismsandpathwaysofadisease.Itisarelativelyyoungindustry.Theycandealwithtargetsinhumansthatmaynotbeaccessiblewithtraditionalmedicines.

BiotechnologyiscommonlyassociatedwithlandmarkbreakthroughsinnewmedicaltherapiestotreathepatitisB,hepatitisC,cancers,arthritis,haemophilia,bonefractures,multiplesclerosis,andcardiovasculardisorders.Thebiotechnologyindustryhasalsobeeninstrumentalindevelopingmoleculardiagnosticdevicesthatcanbeusedtodefinethetargetpatientpopulationforagivenbiopharmaceutical.

Modernbiotechnologycanbeusedtomanufactureexistingmedicinesrelativelyeasilyandcheaply.Thefirstgeneticallyengineeredproductsweremedicinesdesignedtotreathumandiseases.Modernbiotechnologyhasevolved,makingitpossibletoproducemoreeasilyandrelativelycheaplyhumangrowthhormone,clottingfactorsforhemophiliacs,fertilitydrugs,erythropoietinandotherdrugs.Mostdrugstodayarebasedonabout500moleculartargets.Genomicknowledgeofthegenesinvolvedindiseases,diseasepathways,anddrug-responsesitesareexpectedtoleadtothediscoveryofthousandsmorenewtargets.

1.2.2Agricultureandfood

AgricultureandFoodismoreimportanteconomicallythanhealth-care,eveninwesterncountries,andisclearlyofmuchgreaterconcerntotherestoftheworld.

Biotechnologyhasbeenwidelyusedinagricultureandfoodinmanyareas.Forexample,usingthetechniquesofmodernbiotechnology,oneortwogenesmaybetransferredtoahighlydevelopedcropvarietytoimpartanewcharacterthatwouldincreaseitsyield.Moreover,cropscontaininggenesthatwillenablethemto

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生物技术导论教案-天津科技高校

withstandenvironmentalstressesmaybedeveloped.

Biotechnologicalmethodsforimprovingfieldcrops,suchaswheat,cornandsoybeans,arealsobeingsought,sinceseedsservebothasasourceofnutritionforpeopleandanimalsandasthematerialforproducingthenextplantgeneration.Byincreasingthequalityandquantityofproteinorvaryingthetypesinthesecrops,wecanimprovetheirnutritionalvalue.

Modernbiotechnologycanalsobeusedtoslowdowntheprocessofspoilagesothatfruitcanripenlongerontheplantandthenbetransportedtotheconsumerwithastillreasonableshelflife.Thisaltersthetaste,textureandappearanceofthefruit.Moreimportantly,itcouldexpandthemarketforfarmersindevelopingcountriesduetothereductioninspoilage.

1.2.3Otherindustries

Manyotherindustriescould,inprinciple,benefitfrombiotechnology.Thefabricandtextilesindustriesareusingbiotechnologyquitesubstantially,usingenzymestotreattextilesandleather,forexample.Thepaperpulpindustryistakingupbiotechnologyrapidlyasacleaneralternativetochemicalandmechanicalprocesses.Theplasticsindustryalsousessomepolymersmadebymicro-organisms.

Otherbiomaterialssuchasxanthangumsareusedinsomespecializedindustrialapplications,butthisisrareandopportunistic,andusuallydoesnotexploitoursystematicknowledgeofbiologicalsystems,butonlyouraccidentalknowledgeoftheirpropertiesandproducts.Thisisbecauseoilisverycheap,andtheindustryforconvertingitintoproductsisflexible,efficientandsophisticated.

1.3Publicperceptionofbiotechnology

Whilebiotechnologypresentsenormouspotentialforhealthcareandtheproduction,processingandqualityoffoodsthroughgeneticengineeringofcrops,fertilizers,pesticides,vaccinesandvariousanimalspecies,theimplicationsofthesenewbiotechnologicalprocessesgowellbeyondthetechnicalbenefitsoffered.

Centraltomostofthedebatesaboutbiotechnologyisthesinglemainissue–shouldregulationbedependentonthecharacteristicsoftheproductsmodifiedby(rDNA)technology?Theproductversusprocessdebatehascontinuedformanyyearsandexposesconflictingviewsonwhatshouldrepresentpublicpoliciesonnewtechnologydevelopment.Whatispublicinterest?Shouldthisbelefttothescientistsandtechnologiststodecide,orshouldthe‘public’becomepartofsuchdecision-makingprocesses?Themanycrucialdecisionstobemadewillaffectthe

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生物技术导论教案-天津科技高校

futureofhumanityandtheplanet’snaturalresources.

Infact,publicdebateisessentialfornewbiotechnologytogrowup,andundoubtedlyfortheforeseeablefuturebiotechnologywillbeunderscrutiny.Publicunderstandingofthesenewtechnologiescouldwellhastenpublicacceptance.However,thelowlevelofscientificliteracy(e.g.intheUSAwhereonly7%arescientificallyliterate)doesmeanthatmostofthepublicwillnotbeabletodrawinformedconclusionsaboutimportantbiotechnologyissues.Consequently,itisconceivablethatasmallnumberofactivistsmightarguethecaseagainstgeneticengineeringinsuchemotiveandill-reasonedwaysthatboththepublicandthepoliticiansaremisled.Thebiotechnologycommunityneedstositupandtakenoticeof,andworkwith,thepublic.Peopleinfluencedecision-makingbygovernmentsthroughtheballotboxorthroughthepresenceofpublicopinion.

Whilegeneticengineeringisanimmenselycomplicatedsubject,noteasilyexplained,thatdoesn’tmeanthatitmustremain,indecision-makingterms,onlyinthecontrolofthescientist,industrialistorpolitician.Thereisnodoubtthatmanyofthepublicorconsumersareinterestedinthescienceofgeneticengineeringbutareunabletounderstandthecomplexityofthissubject.Furthermore,geneticengineeringanditsmyriadofimplicationsmustnotbebeyonddebate.Publicattitudestogeneticengineeringwillinfluenceitsevolutionandmarketplaceapplications.Itisimportantforpublicconfidenceforeveryonetorecognizethatallscienceisfallible-especiallycomplexbiologicalscience.AlltoooftenpressandTVreportsongeneticengineeringpresentthediscoveriesasabsolutecertaintieswhenthisisrarelythecase

1.4Productsafety

Muchdebateisnowtakingplaceonthesafetyandethicalaspectsofgeneticallymodifiedorganisms(GMOs)andtheirproductsdestinedforpublicconsumption.Cansuchproductswith‘unnatural’genechangesleadtounforeseenproblemsforpresentandfuturegenerations?

Thesafetyofthehumanfoodsupplyisofcriticalimportancetomostnationsandallfoodsshouldbefitforconsumptioni.e.notinjurioustohealthorcontaminated.WhenfoodsorfoodingredientsarederivedfromGMOstheymustbeseentobeassafeas,orsaferthan,theirtraditionalcounterparts.Theconceptofsubstantialequivalenceiswidelyappliedinthedeterminationofsafetybycomparisonwithanalogousconventionalfoodproductstogetherwithintendeduseandexposure.

Whensuchnovelproductsaremovingintothemarketplacetheconsumermustbeassuredoftheirqualityandsafety.Thustheremustbetoxicologicalandnutritional

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生物技术导论教案-天津科技高校

guidanceintheevolutionofnovelfoodsandingredientstohighlightanypotentialriskswhichcanthenbedealtwithappropriately.Safetyassessmentofnovelfoodsandfoodingredientsmustsatisfytheproducer,themanufacture,thelegislatorandtheconsumer.Theapproachshouldbeinlinewithacceptedscientificconsiderations,theresultsofthesafetyassessmentmustbereproducibleandacceptabletoresponsiblehealthauthoritiesandtheoutcomemustsatisfyandconvincetheconsumer.

Inbiotechnology,governmentalregulationswillrepresentacriticaldeterminantofthetimeandtotalcostsinbringingaproducttomarket.Regulatoryagenciescanactas‘gate-keepers’forthedevelopmentandavailabilityofnewbiotechnologyproducts,butcanalsoerectconsiderablebarrierstoindustrialdevelopment.

1.5Thefutureofbiotechnology

BiotechnologyisincreasinglybeingviewedasaPrometheanscience,becauseinsomanywaysitistransformingtherelationshipbetweenhumansandtheplanet.Inrecentyearsbiotechnologyhasbeenshowntobeaspectrumofenablingtechnologies,whichareincreasinglybeingappliedinmanyaspectsofmodernsociety.Acentralfeatureofnewbiotechnologicaladvancesderivesfromanincreasingunderstandingofthemechanismsoflifeandhowthesewilleventuallytransformhumanlives,aswellasgivingadeeperappreciationofagriculture,aquaculture,forestryandthebiologicalenvironment.Theabilitytoselectandmanipulategeneticmaterialwithinandoutsidespecieshaspermittedunprecedentedopportunitiestoalterlifeformsforthebenefitofsociety.

ManymolecularbiologistshavepostulatedthatageneticorDNAsequenceanalysisofaninpidualcouldbepredictiveoffuturediseaseoccurrence,e.g.cardiovascular,cancer,Alzheimer’s,etc.Undoubtedly,therewillbecontinuedresearchandapplicationinthisarea.Thefurtherimplementationofgenomicsandproteomicswillallowamuchdeeperunderstandingofthebiologyofmolecules,cellsandwholeorganisms.Doctorsandpatientswillhavemuchtogainfromtheoutcomeofthesestudies.Muchwillbelearnedabouthumaninpidualityandhowthesefindingscouldinfluenceinpidualhealthanddiseasesusceptibility.

Plant-basedgeneticengineeringstartedintheearly1980swiththedevelopmentoftheTiplasmidofAgrobacterium,whichhasallowedtheintroductionofsimplegeneticconstructsintomostoftheimportantcropplants.ThereisincreasingevidencethatGMcropsaregivingsignificantyieldincreases,savingsforgrowersandpesticideusereductionsinbothdevelopedanddevelopingcountries.YetanotherimportantfeatureofcertainGMplantsisthattheyuselesswater,andundoubtedlyinmany

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partsoftheworldwateravailabilitywillbethedeterminingfactorforsuccessfulfoodproductionbybothanimalsandplants.

Thenewaspectsofbiotechnologysuchasbiofuelwillbringhugebenefitstohumankind.Climatechangeisnowaworldwiderecognizedconcern.Anumberofapproachesarenowbeingconsideredtocountertheeffectsofglobalwarming.Fromabiotechnologicalconsiderationbiofueldevelopmenthasgainedinternationalrecognitionandawiderangeofoptionsarebeingprogressedtodeterminewhichbiofuelscanbecomecost-effectivealternativestofossilfuels..

Insummary,biotechnologywillplayamajorroleinthecontinuedsearchforsolutionstothemanyproblemsthatwillaffectthesocietyoftomorrow:health,foodsupplyandasafebiologicalenvironment.Andmorescientificresearchwillbecontinuedtoachievetheseends.

1.6Furtherreading

FumentoM.(2023).Bioevolution:HowBiotechnologyisChangingourWorld.EncounterBooks,USA.

JohnE.Smith(2023).Biotechnology(5thedition).CambridgeUniversityPress,UK.

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生物技术导论教案-天津科技高校

Chapter2Bioreactor

Bioreactorsarethecontainmentvehiclesofanybiotechnology-basedproductionprocess,beitforbrewing,organicoraminoacids,antibiotics,enzymes,vaccinesorforbioremediation.Foreachbiotechnologyprocessthemostsuitablecontainmentsystemmustbedesignedtogivethecor-rectenvironmentforoptimisingthegrowthandmetabolicactivityofthebiocatalyst.Bioreactorsrangefromsimplestirredornon-stirredopencon-tainerstocomplexasepticintegratedsystemsinvolvingvaryinglevelsofadvancedcomputercontrol(Fig.1).

Bioreactorsoccurintwodistincttypes(Fig.1.Inthe?rstinstancetheyareprimarilynon-asepticsystemswhereitisnotabsolutelyessentialtooperatewithentirelypurecultures,e.g.brewing,ef?uentdisposalsys-tems;whileinthesecondtype,asepticconditionsareaprerequisiteforsuccessfulproductformation,e.g.antibiotics,vitamins,polysaccharidesandrecombinantproteins.Thistypeofprocessinvolvesconsiderablechal-lengesonthepartofengineeringconstructionandoperation.Thephysicalformofmanyofthemostwidelyusedbioreactorshasnotalteredmuchoverthepastfortyyears;however,inrecentyears,novelformsofbioreactorshavebeendevelopedtosuittheneedsofspeci?cbioprocessesandsuchinnovationsare?ndingincreasinglyspecialisedrolesinbioprocesstechnology(Fig.

1).

Inallformsoffermentationtheultimateaimistoensurethatallpartsofthesystemaresubjecttothesameconditions.Withinthebioreactorthemicroorganismsaresuspendedintheaqueousnutrientmediumcon-tainingthenecessarysubstratesforgrowthoftheorganismandrequiredproductformation.Allnutrients,includingoxygen,mustbeprovidedtodiffuseintoeachcellandwasteproductssuchasheat,carbondioxideandwastemetabolitesremoved.

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生物技术导论教案-天津科技高校

Fig.1Variousformsofbioreactor.

(a)Continuousstirredtankreactor.

(b)Towerreactor.

(c)Loop(recycle)bioreactor.

(d)Anaerobicdigesterorbioreactor.

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生物技术导论教案-天津科技高校

(e)Activatedsludgebioreactor.(Source:(a)and(b)reproducedbypermissionfromKristiansenandChamberlain,1983.)

Table1Standardsofmaterialsusedinsophisticatedfermenterdesign

Theconcentrationofthenutrientsinthevicinityoftheorganismmustbeheldwithinade?niterangesincelowvalueswilllimittherateoforgan-ismmetabolismwhileexcessiveconcentrationscanbetoxic.Biologicalreactionsrunmostef?cientlywithinoptimumrangesofenvironmentalparameters,andinbiotechnologicalprocessestheseconditionsmustbeprovidedonamicro-scalesothateachcellisequallyprovidedfor.Whenthelargescaleofmanybioreactorsystemsisconsidereditwillberealizedhowdif?cultitistoachievetheseconditionsinawholepopulation.Itisherethattheskillsoftheprocessorbiochemicalengineerandthemicro-biologistmustcometogether.

Fermentationreactionsaremultiphase,involvingagasphase(containingN2,O2andCO2),oneormoreliquidphases(aqueousmediumandliquidsubstrate)andsolidmicrophase(themicroorganismsandpossiblysolidsubstrates).Allphasesmustbekeptinclosecontacttoachieverapidmassandheattransfer.Inaperfectlymixedbioreactorallreactantsenteringthesystemmustbeimmediatelymixedanduniformlydistributedtoensurehomogeneityinsidethereactor.

Toachieveoptimisationofthebioreactorsystem,thefollowingoperatingguidelinesmustbecloselyadheredto:

(1)thebioreactorshouldbedesignedtoexcludeentranceofcontaminatingorganismsaswellascontainingthedesiredorganisms

(2)theculturevolumeshouldremainconstant,i.e.noleakageorevaporation

(3)thedissolvedoxygenlevelmustbemaintainedabovecriticallevelsofaerationandcultureagitationforaerobicorganisms

(4)environmentalparameterssuchastemperature,pH,etc.,mustbecon-trolledandtheculturevolumemustbewellmixed.

Thestandardofmaterialsusedintheconstructionofsophisticatedfermentersis

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生物技术导论教案-天津科技高校

important(Table1).

Fermentationtechnologistsseektoachieveamaximisationofculturepotentialbyaccuratecontrolofthebioreactorenvironment.Butstillthereisagreatlackoftrueunderstandingofjustwhatenvironmentalconditionswillproduceanoptimalyieldoforganismorproduct.Organismswithlargecellsize,suchasanimalcellscomparedtobacteria,haveacomplexdemandfornutrientsandlowergrowthrate.Ontheotherhandtheirabilitytoproducecomplicatedproteinsisincreased.

Successfulbioprocessingwillonlyoccurwhenallthespeci?cgrowth-relatedparametersarebroughttogether,andtheinformationusedtoimproveandoptimisetheprocess.Forsuccessfulcommercialoperationofthesebioprocessesquantitativedescriptionofthecellularprocessesisanessentialprerequisite:thetwomostrelevantaspects,yieldandproductivity,arequantitativemeasuresthatwillindicatehowthecellsconvertthesubstrateintotheproduct.Theyieldrepresentstheamountofproductobtainedfromthesubstratewhiletheproductivityspeci?estherateofproductformation.

Tounderstandandcontrolafermentationprocessitisnecessarytoknowthestate

oftheprocessoverasmalltimeincrementand,further,toknowhowtheorganismrespondstoasetofmeasurableenvironmentalconditions.Processoptimisationrequiresaccurateandrapidfeedbackcontrol.Inthefuture,thecomputerwillbeanintegralpartofmostbioreactorsystems.However,thereisalackofgoodsensorprobesthatwillallowon-lineanalysistobemadeonthechemicalcomponentsofthefermentationprocess.

Alargeworldwidemarketexistsforthedevelopmentofnewrapidmethodsmonitoringthemanyreactionswithinabioreactor.Inparticular,thegreatestneedis

forinnovatorymicroelectronicdesigns.

Whenendeavouringtoimproveexistingprocessoperationsordesignitisoftenadvisabletosetupmathematicalmodelsoftheoverallsystem.Amodelisasetofrelationshipsbetweenthevariablesinthesystembeingstudied.Suchrelationshipsareusuallyexpressedintheformofmathe-maticalequationsbutcanalsobespeci?edascause/effectrelationships,whichcanbeusedintheoperationofthespeci?cprocesses.Theactualvariablesinvolvedcanbeextensivebutwillincludeanyparameterthatis

ofimportancefortheprocessandcaninclude:pH,temperature,substrateconcentration,agitation,feedrate,etc.

Bioreactorcon?gurationshavechangedconsiderablyoverthelastfewdecades.Theoriginalfermentationsystemwasashallowtankagitatedorstirredbymanpower.

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生物技术导论教案-天津科技高校

Fromthishasdevelopedthebasicaerationtowersystem,whichnowdominatesindustrialusage.Asfermentationsystemswerefurtherdeveloped,twodesignsolutionstotheproblemsofaerationandagitationhavebeenimplemented.The?rstapproachusesmechanicalaerationandagitationdevices,withrelativelyhighpowerrequirements;thestandardexampleisthecentrallystirredtankreactor(CSTR),whichiswidelyusedthroughoutconventionallaboratoryandindustrialfermentations.Suchbioreactorsensuregoodgas/liquidmasstransfer,havereason-ableheattransfer,andensuregoodmixingofthebioreactorcontents.

TheverticalshaftoftheCSTRwillcarryoneormoreimpellersdependingonsizeofthebioreactor(Fig.1a).Abroadrangeofimpellershavebeeninvestigatedforstirringandcreatinghomogeneousconditionswithinthebioreactor.Theimpellersareusuallyspacedatintervalsequivalenttoonetankdiameteralongtheshafttoavoidaswirlingtypeofliquidmovement.Thesix?at-bladed(Rushton)turbineimpellersareusedinthemajorityofbioreactorsandnormallythreeto?vearemountedtoachievegoodmixinganddispersionthroughoutthesystem.Thefunctionoftheimpellersistocreateagitationormixingwithinthebioreactorandtofacilitateaera-tion.Theprimaryfunctionofagitationistosuspendthecellsandnutrientevenlythroughoutthemedium,toensurethatthenutrients,includingoxygen,areavailabletothecellsandtoallowheattransfer.Mostindustrialorganismsareaerobicand,inmostfermentations,theorganismswillexhibitahighoxygendemand.Sinceoxygenissparinglysolubleinaqueoussolutions(solubilityofCO2inwaterisabout30timeshigherthanthatofO2)aerobicfermentationscanonlybesupportedbyvigorousandconstantaerationofthemedium.

Thesecondmainapproachtoaerobicbioreactordesignusesairdistribution(withlowpowerconsumption)tocreateforcedandcontrolledliquid?owinarecycleorloopbioreactor.Inthiswaythecontentsaresubjectedtoacontrolledrecycle?ow,eitherwithinthebioreactororinvolvinganexternalrecycleloop.Thusstirringhasbeenreplacedbypumping,whichmaybemechanicalorpneumatic,asinthecaseoftheairliftbioreactor.

Thecentrallystirredtankreactorconsistsofacylindricalvesselwithamotor-drivencentralshaftthatsupportsoneorseveralagitatorswiththeshaftenteringeitherthroughthetoporthebottomofthevessels.Theaspectratio(i.e.height-to-diameterratio)ofthevesselisthreeto?veformicrobialsystemswhileformammaliancellculturetheaspectratiosdonotnormallyexceedtwo.Sterileairisspargedintothebioreactorliquidbelowthebottomimpellerbywayofaperforated

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生物技术导论教案-天津科技高校

ringsparger.Thespeedoftheimpellorswillberelatedtothedegreeoffragilityofthecells.Mammaliancellsareextremelyfragilewhencomparedtomostmicroorganisms.Inagreatmanyofthehigh-valueprocessesthebioreactorswillbeoperatedinabatchmannerunderasepticmonoculture.Thebioreactorscanrangefromc.20Ltoinexcessof790m3forparticularprocesses.Theinitialcultureexpansionofthemicroorganismswillcommenceinthesmallestbioreactor,andwhengrowthisoptimiseditwillthenbetransferredtoalargerbioreactor,andsoforth,untilthe?naloperationbioreactor.Throughoutsuchoperationsitisimperativetomaintainasepticconditionstoensurethesuccessoftheprocess.Bioreactorsarenormallysterilisedpriortoinoculationandcontaminationmustbeavoidedduringallsubsequentoperations.Ifcontaminationoccursduringthecultivationthiswillinvariablyleadtoprocessfailuresincemoreoftenthannotthecontaminantcanoutgrowtheparticipatingmonoculture.

Thenumberofdistincttypesofbioreactorisquitelimitedwhenmeasuredagainstthewiderangeofproductionprocessesandthevariedbiologicalsystemsinvolved.Inindustrialpractice,andlessasaresultofspecialadvantagethanasaneedfor?exibilityinproductionequipment,theCSTRnowoccupiesadominantpositionandisvirtuallytheonlybioreactordesignusedinfull-scalebioprocessing.Largeamountsoforganicwastewatersfromdomesticandindustrialsourcesareroutinelytreatedinaerobicandanaerobicsystems.Activatedsludgeprocessesarewidelyusedfortheoxidativetreatmentofsewageandotherliquidwastes(Fig.1d).Suchprocessesusebatchorcontinuousagitatedbioreactorsystemstoincreasetheentrainmentofairtooptimizeoxidativebreakdownoftheorganicmaterial.Thesebioreactorsarelargeandforoptimumfunctioningwillhaveseveralormanyagitatorunitstofacilitatemixingandoxygenuptake.Theyarewidelyusedinmostmunicipalsewagetreatmentplants.

Anaero