Comparison of batch and fed-batch fermentations using cornco

玉米芯分批补料发酵工艺优化

Comparisonofbatchandfed-batchfermentationsusingcorncobhydrolysateforbioethanolproduction

Yi-HuangChanga,Ku-ShangChanga,Cheng-WeiHuangb,Chuan-LiangHsuc, ,Hung-DerJanga,

a

DepartmentofFoodScience,YuanpeiUniversity,Hsinchu300,TaiwanInstituteofFoodScience,YuanpeiUniversity,Hsinchu300,Taiwanc

DepartmentofFoodScience,TunghaiUniversity,Taichung407,Taiwan

b

articleinfoabstract

Theoptimalconditionsforthemaximumproductionofethanolfromcellulosichydrolysateinbatchandfed-batchcultureswereinvestigatedandcompared.Thepretreatedcorncobcouldbeconvertedintoreducingsugarwithmaximalyieldsaftertheenzymemixtureswerefed.After48hofhydrolyticreaction,overallreducingsugarandglucoseconcentrationsreached0.61and0.36g/gdriedsubstrate,respectively.FurtherbatchfermentationofcellulosichydrolysatewasperformedusingbatchculturesofSaccharomy-cescerevisiaeBCRC21812,23.3–41.1g/lbiomassand6.9–23.0g/lethanolwasobtained.Forthefed-batchfermentation,theeffectsoffeedingglucoseconcentrationsonethanolfermentationwerestudied.Thefeedingglucoseconcentrationof30g/lresultedinahigherethanolyieldthanthatof20g/land10g/ldid.Thecellbiomass,ethanolyields,andethanolconversionrateforthefed-batchfermentation,feedingat30g/lglucoseconcentration,were44.5g/l,32.3g/land0.64gethanol/gglucose,respectively.Theresultsindicatethatthefed-batchfermentationhadahigherethanolyieldthanthatofthebatchfermentation.

Ó2012ElsevierLtd.Allrightsreserved.

Articlehistory:

Received31January2011

Receivedinrevisedform5February2012Accepted6February2012

Availableonline18February2012Keywords:

CellulosichydrolysatesBatchfermentation

Fed-batchfermentationBioethanol

1.Introduction

Tolessentheworld’sdependenceonnon-renewableresources,useofagriculturalbiomassfortheproductionofbiofuelssuchasbioethanolhasdrawnmuchattentiontomanyresearchersinthepastfewdecades.Cellulosicbiomassisanidealsourceofenergybecauseitisbothrenewableandavailableinlargequantitiesaroundtheworld.However,theprocessfortheproductionofethanolfromcellulosicmaterialsismorecomplicatedthanitsproductionfromsugarorstarch-basedones.Speci cally,therearetechnicalandeconomicalimpedimentsinregardstothedevel-opmentofcommercialprocessesthatutilizecellulosicbiomass.Technologiesthatwillallowforthecost-effectiveconversionofcellulosicbiomassintofuelsandotherchemicalsarebeingdevel-oped.Thesetechnologiesincludelow-costthermoorchemicalpre-treatment,highlyeffectivecellulasesandhemicellulases,andef cientandrobustfermentativemicroorganisms,havemadethecommercializationofbiofuelproductionmuchmorepromising[1–3].

Forproductionofbioethanol,alowerrawmaterialprice,togetherwithahighethanolyieldandef cientenzymes,willde-creasetheproductioncostsigni cantly.Severaldifferentpretreat-mentmethodshavebeenusedtofacilitatetheenzymaticCorrespondingauthors.Tel.:+886423590121x37306;fax:+886423599059

(C.-L.Hsu),tel.:+88635381183x8482;fax:+88636102342(H.-D.Jang).

E-mailaddress:hungder@mail.ypu.edu.tw(H.-D.Jang).

0016-2361/$-seefrontmatterÓ2012ElsevierLtd.Allrightsreserved.doi:10.1016/j.fuel.2012.02.006

hydrolysisoflignocellulosicmaterial[4].Anef cientprocessforobtainingreducingsugarsfromlignocellulosicmaterialistousechemical/physicalpretreatment,followedbyenzymatichydroly-sis.Thehydrolysisofnaturallignocellulosetoglucosedependsonthesynergyofenzymessystem,i.e.,b-1,4-endoglucanase,b-1,4-exoglucanaseandb-glucosidase[5],andb-1,4-endoxylanase.Thesecellulolyticenzymeshavebeenappliedtoincreasethehydrolysisef ciencyofcellulosicmaterials[6].

Manydifferenttypesofprocessesforethanolfermentationhavebeenproposed,includingbatchfermentation,continuousfermen-tation,continuousfermentationwithcellrecycling,fed-batchcul-turesandrepeated-batchcultures[7].Batchfermentationprocessisusedextensivelytoconvertsugarstoethanolfortheproductionofbeveragesandbiofuels.Asforfed-batchfermentation,theinter-mittentadditionofglucose,withouttheremovalofthefermenta-tionbroth,intothefed-batchcultureisoneofthemostcommonmethodsfortheproductionofethanolintheindustry.Theadvan-tagesofthisprocessincludethereductionofsubstrateandend-productinhibition,higherproductivityofethanol,higherdissolvedoxygenrate,decreasedfermentationtime,andhighersacchari ca-tionrate[8].Fed-batchfermentationhasbeenreportedasagoodprocessforethanolproductionwhenperformedondifferentrawmaterialssuchascornstover[9]andrecycledpaper-derivedmaterial[10].

Evenconversionofcorncobhydrolysatetobioethanoleitherbybatchfermentation[1,11]orbyfed-batchfermentation[12,13]separatelyhasbeenstudiedinthepast,thesimultaneous