4微生物培养基Culturalmedium

4.微生物培养基CulturalmediaAculturalmediumisthesubstanceinwhichaspecificorganismlivesandgrows.Itmustcontaintheessentialnutrientsneededforthemicrobetogrow.Agoodmediumisveryimportanttothesuccessofanindustrialfermentation.Themediumsuppliesnutrientsforgrowth,energy,buildingofcellsubstance,andbiosynthesisoffermentationproducts.4.1培养基的类型及功能Classificationsofmediaandtheirfunctions按纯度分类：--合成培养基chemicallydefinedmedia:compoundidentityandconcentrationofallcomponentsareknown.Syntheticmedia--天然培养基chemicallyundefinedmedia:ingredientsincludeoneormorechemicallycomplexsubstancessuchasproteinhydrolysatesandextracts.CrudemediaThechoiceofdefinedorundefinedmediumisdependentuponitsapplication.---Chemicallydefinedmediaareusefulinbiochemicalormetabolicstudiesoforganisms.--Generallaboratorygrowthmediaandindustrialmediaareoftenchemicallycomplex.Suchas花生饼、蛋白胨等。一般不需外加微量元素(traceelements)、维生素等。按状态分类：-Solidmedia：suitabletocultureandpreservespeciesandspores;cultivatingfungi.-Liquidmedia:80%-90%water,industrialfermentationmedia.-Semi-solidmedia:liquidmedium+agar主要用于鉴定细菌、观察细菌运动特征等。按用途分类孢子培养基、种子培养基和发酵培养基1.孢子培养基sporemedia要求：使菌体迅速生长，产生较多的优质孢子，不易引起菌种发生变异(variation)。基本配制要求：⑴notrichinnutrition,especiallyorganicnitrogensoure.⑵optimalmineralsaltconcentration⑶optimalpHandhumidity生产上常用孢子培养基：麸皮、大米、小米培养基；由葡萄糖、蛋白胨、牛肉膏和食盐等配制的琼脂斜面培养基。大米和小米常用作霉菌孢子培养基，因它们含氮少、疏松、表面积大，是较好的孢子培养基。水分控制在21％－25％。种子培养基inoculummedia:种子培养基是供孢子发芽、生长和大量繁殖菌丝体，并使菌丝体长得粗壮，成为活力强的‘种子’。Inoculummediaareusuallylessnutritiousthanareproductionmedia,andtheyusuallycontainaconsiderablylowerlevelofthemainnutritivecarbonsource.一般种子培养基常包括有机氮源和无机氮源最后一级的种子培养基的成分最好接近发酵培养基。发酵培养基productionmedia发酵培养基是供菌体生长、繁殖和合成产物之用。要求：既要使种子接种后能迅速生长，达到一定的菌丝浓度，又要使长好的菌体迅速合成所需产物。配制要求：其组成除有菌体生长所必需的元素和化合物外，还需有合成产物所需的特定元素、前体和促进剂等。Inadditiontothecarbonandnitrogencompounds,amediumcontainsinorganicsalts,vitamins,growthfactors,precursorsoffermentationproducts.Microbialgrowthunderindustrialfermentationconditionsusuallyutilizesa“luxurymetabolism”oftheorganisms.Thus,goodyieldsoffermentationproductsoccuronlyifrelativelylargeamountsofcarbon,andpossiblynitrogen,arechanneledthroughthemetabolicpathwaysofthemicroorganism.4.2发酵培养基的成分及来源CompositionofmediaandtheirsourcesTheparticularcompositionofafermentationmediumcanbesimpletocomplexdependingontheparticularmicroorganismanditsfermentation.Autotrophic(自养的)microorganismsrequireonlythesimplestofinor-ganicmedia.Heterotrophic(异养的)microorganismslacktheabilitytosynthesizemanyoftheirsustenanceandgrowthrequirements.4.2.1碳源carbonsourcesCarbonsourceisoneofmaincompositionofmedia.Thefunctionsare:providingcarbonsandenergy;thecomponentsforsynthesisofproducts.Thesecanincludesimplesugars,complexcarbohydrates,alcohols,aminoandotherorganicacids,andshort-chainlipids.常用的碳源有糖类、油脂、有机酸和低碳醇。蛋白质、氨基酸也可用作碳源。4.2.1.1糖类sugarsSugarsusedmainly:glucose,molasses(糖蜜),dextrin(糊精).Glucose:mostmicrobescanutilizeit.速效碳源、highconcentrationspeedrespirationupDOnoenoughintermediates(中间产物）accumulationinhibitinggrowthmolasses(糖蜜)Beet(甜菜)andcanemolassesareby-productsofthesugarindustry.containing50%-75%fermentablesugars,mainlysucrose.Alsocontainingnitrogenouscompounds,vitaminsandminerals.CheaperStarchanddextrin(糊精)Starch:----widelyusedinfermentationindustry---starchhydrolyzeusingmicrobialamylasedextringlucose-Mostcommonusedstarches:corn,wheat,potatostarches.Alsousingcornflour.--advantages:缓效碳源、cheaperthanglucose油和脂肪oilsandfatsOilandfatsarealsousedascarbonsourcesbecausesomemicrobescontainlipase(脂肪酶)Fatglycerol(甘油)andfattyacidsoxidizeCO2+water,releasingmuchenergyProvidingenoughO2isimportant.常用的油：豆油、菜子油、猪油、鱼油、棉子油等。有机酸organicacidsSomemicrobescanuseorganicacidsascarbonsources,suchaslacticacid,citricacid,aceticacid.pHofculturalmediumwillincrease.CH3COONa+O22CO2+H2O+NaOH烃和醇类hydrocarbonandethanol石油及裂解产物如正烷烃也可用作carbonsources.自然界中能同化乙醇的微生物和能同化糖质的微生物一样普遍。4.2.2氮源nitrogensources氮源主要用于构成细胞物质（氨基酸、蛋白质、核酸等）和含氮代谢物。有机氮源organicnitrogensources常用的:花生饼、棉子饼、玉米浆、玉米蛋白粉、蛋白胨、酵母粉、鱼粉、蚕蛹粉、尿素、废菌丝体和酒糟等。organicnitrogensourcesmicrobialproteinaseaminoacidsmetabolizedbymicrobes.organicnitrogensourcescontainrichproteins,peptides,aminoacids,vitaminsandgrowthfactors.在含有机碳源的培养基中，微生物常表现出生长旺盛、菌丝或细胞浓度增长迅速的特点。有些微生物对氨基酸有特殊的需求。如缬氨酸可提高红霉素的发酵单位。玉米浆CornsteepLiquorCornsteepliquoristhewaterextractby-productresultingfromthesteeping(浸泡)ofcornduringthecommercialproductionofcornstarchandothercornproducts.Ofthe50%solidsofcornsteepliquor,nearlyhalfislacticacid.Therestincludesaminoacids,glucoseandotherreducingsugars,salts,vitamins,andprecursors(前体)suchasthoseforthepenicillinmolecule.Thehighlacticacidcontentofcornsteepliquorresultsfromthegrowthoflacticacidbacteriaduringitsmanufacture.Thisvariationincomposition,attimes,canleadtopoorreproducibilityofanindustrialfermentation.尿素ureaUreaisalsoacommonlyusednitrogensource.Itsfeature:---singlecomponent,nonutritionalfeatureofcomplexnitrogensources;---cheaper,oftenusedinproductionofpenicillinandglutamicacid.yeastextractpeptones有机氮源除了作为菌体生长繁殖的营养外，有的还是产物的前体。缬氨酸、半胱氨酸和-是合成青霉素和头孢菌素的主要前体；甘氨酸可作为L-丝氨酸的前体等。无机氮源i