Comparison of batch and fed-batch fermentations using cornco(2)

玉米芯分批补料发酵工艺优化

Y.-H.Changetal./Fuel97(2012)166–173167

comparisonoftheef cienciesofbothbatchandfed-fermentationsbythesamecellulosichydrolysatewererare.Additionally,theim-pactofdifferentfermentationtreatments,i.e.batchandfed-batch,ofcellulosichydrolysateonthedynamicsofmicrobialgrowthandethanolproductionrateintherespectivefermentorswereseldomevaluated.Inthiswork,thehydrolysisprocessofthecorncobsub-strateusingpretreatmentwithacid,autoclavingandthenhydroly-siswiththeenzymemixtureswasexamined.Thefermentationprocessesandkineticsofthecorncobhydrolysateinthebatchandfed-batchculturesofSaccharomycescerevisiaeBCRC21812werealsocompared.

Acidpretreatmentwasperformedwith1%(v/v)sulfuricacidfor30minatasolid-to-liquidratioof1:10.Themixturewas ltered.Thenthe ltratewasfurtherhydrolyzedbyautoclavingat121°Cfor60min,accordingtotheproceduresdescribedinourpreviousreport[14].Afterthepretreatment,thecellulosicresiduewassoakedindistilledwaterandincubatedinwaterbathat50°Cfor30min,andthen ltered.

2.2.Microorganismsandcultivation

ThestrainofS.cerevisiaeBCRC21812,purchasedfromBiore-sourcesCollectionandResearchCenter,FIRDI(Hsinchu,Taiwan),wasusedasaninoculumforethanolfermentation.S.cerevisiaeBCRC21812istraditionallyusedforalcoholicbeverageandbioeth-anolproduction.IthadbeenfoundthatS.cerevisiaeBCRC21812couldgrowwellinYPDmediainthepresenceof8%(v/v)ethanolaccordingtoourpreviouspreliminarystudy.YeastculturesweremaintainedinaYPDmediumcontaining2%(w/v)dextrose,1%(w/v)peptoneand0.5%(w/v)yeastextractat25°Cfor48h.TheinitialpHwasadjustedto6.5either1NHClorNaOHpriortoster-ilizationat121°Cfor20min.

2.3.Hydrolysisofcellulosicresiduebytreatmentwiththeenzymemixture

Themixtureofprehydrolysateobtainedfromtheacidandauto-clavingpretreatmentswascollectedand lteredwithWhatman

2.Materialsandmethods

2.1.Cellulosicmaterialandpretreatment

Thecorncobmaterials,purchasedfromalocalmarket,wereoven-driedfor24hat50°C,groundedintoparticles(diameter2–10mm)andstoredinpillvialsat25°C.Thecorncobmaterialsconsistedmainlyof42%(w/w)celluloseand28%(w/w)hemicellu-lose,whichcouldbehydrolyzedtoreducingsugar.Inaddition,therewas20%oflignininthecorncobmaterials.Therestwereashesandminorcomponents.Thestructuralcarbohydrateandlig-nininbiomassweredeterminedaccordingtoStandardBiomassAnalyticalProceduresofNationalRenewableEnergyLaboratory(NREL).