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1、Chapter4CellDisruption第四章細(xì)胞破碎※4.1?CellMembranes細(xì)胞膜※4.0Summary概述※4.2??ChemicalMethods化學(xué)破碎方法※4.3mechanicaldisruption機(jī)械破碎※4.0Summary概述Bioseparationsusuallybeginwiththeseparationofbiomassfrombroth.TheseparationcommonlyusesfiltrationorcentrifugationasdescribedinChapters2and3.Inmanycases,thedesiredpr
2、oductisinthebroth.Antibiotics,arecommonlyinthebroth;soareextracellularenzymes,manypolysaccharides,andmostaminoacids.Inallthesecases,theseparatedbrothcanbetreatedtoisolateandpurifytheproduct,asabyproduct.生物分離的第一步是將生物機(jī)體從發(fā)酵液中分離，通常使用過(guò)濾和離心等方法，這在第二、三章中已有陳述。大多數(shù)情況下，抗生素，胞外酶，一些多糖，及氨基酸等目標(biāo)產(chǎn)物存在于在發(fā)酵液中。在上述過(guò)程中
3、，需被分離的發(fā)酵液可被看作一種副產(chǎn)物來(lái)處理，以此分離和純化產(chǎn)物。Insomecases,theproductsofinterestarenotinthebrothbutareinthebiomass.Inparticular,mostproteinsproducedinquantitybygeneticallymanipulatedbacteriaarenotexcretedintothebroth,butareprecipitatedwithinthecell.Lipidsandsomeantibioticsarealsotrappedinthebiomass.Inafewcase
4、s,likebaker’syeast,thedesiredproductisthecellmassitself.Inafewothers,desiredproductslikesteroidscanbeextractedwithoutrupturingthecells.Inmanycases,theproductistrappedinthebiomass:Itisintracellular.有些目標(biāo)產(chǎn)物不在發(fā)酵液中，而是存在于生物體中。尤其是由基因工程菌產(chǎn)生的大多數(shù)蛋白質(zhì)不會(huì)被分泌到發(fā)酵液中，而是在細(xì)胞內(nèi)沉積。脂類物質(zhì)和一些抗生素也是包含在生物體中。還有一些目標(biāo)產(chǎn)物就是細(xì)胞本身，如面
5、包酵母。還有，產(chǎn)物如類固醇不必通過(guò)細(xì)胞破碎提取。大多數(shù)情況下，產(chǎn)物還是包裹在生物體內(nèi)，屬胞內(nèi)產(chǎn)物。Releasingthistrappedmaterialusuallyinvolvesrupturingthecellwall,andisthesubjectofthisshortchapter.Themethodsofcellrupturehavelargelybeendevelopedinbiochemistry,andhenceareofsmallscale.Theirapplicationtothelargerscaleoperationsimpliedbygeneticengi
6、neeringisspeculative.Theequipmentwhichisusedisnotdesignedforbiotechnology.使胞內(nèi)產(chǎn)物釋放出來(lái)一般需要破碎細(xì)胞壁，這也是這一章的主題。細(xì)胞破碎的方法在生物化學(xué)領(lǐng)域中得到了很廣泛的運(yùn)用，但多數(shù)在小規(guī)模生產(chǎn)中，在大規(guī)模生產(chǎn)尤其是基因工程中應(yīng)用極少。Inthischapter,webegininSection4.1byreviewingthestructureofthecellwall.Wethenconsiderthemethodsforcellrupturemostlikelytobeusefulatlargers
7、cales.Thesemethods,listedinTable4.0-1,areconvenientlysplitintotwogroups,describedas“chemical”and“mechanical.”InthechemicalmethodsdetailedinSection4.2,thecellmembraneisrupturedbyosmoticpressure,dissolvedbydetergents,orenfeebledbyor
