Lignocellulose Conversion: Enzymatic and Microbial Tools for Bioethanol Production PDF
Preview Lignocellulose Conversion: Enzymatic and Microbial Tools for Bioethanol Production
Vincenza Faraco Editor Lignocellulose Conversion Enzymatic and Microbial Tools for Bioethanol Production Lignocellulose Conversion Vincenza Faraco Editor Lignocellulose Conversion Enzymatic and Microbial Tools for Bioethanol Production 123 Editor Vincenza Faraco Department of Chemical Sciences Universityof Naples‘‘FedericoII’’ Complesso Universitario MonteS.Angelo Naples Italy ISBN 978-3-642-37860-7 ISBN 978-3-642-37861-4 (eBook) DOI 10.1007/978-3-642-37861-4 SpringerHeidelbergNewYorkDordrechtLondon LibraryofCongressControlNumber:2013940305 (cid:2)Springer-VerlagBerlinHeidelberg2013 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpartof the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation,broadcasting,reproductiononmicrofilmsorinanyotherphysicalway,andtransmissionor informationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilar methodology now known or hereafter developed. Exempted from this legal reservation are brief excerpts in connection with reviews or scholarly analysis or material supplied specifically for the purposeofbeingenteredandexecutedonacomputersystem,forexclusiveusebythepurchaserofthe work. Duplication of this publication or parts thereof is permitted only under the provisions of theCopyright Law of the Publisher’s location, in its current version, and permission for use must always be obtained from Springer. Permissions for use may be obtained through RightsLink at the CopyrightClearanceCenter.ViolationsareliabletoprosecutionundertherespectiveCopyrightLaw. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publicationdoesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexempt fromtherelevantprotectivelawsandregulationsandthereforefreeforgeneraluse. While the advice and information in this book are believed to be true and accurate at the date of publication,neithertheauthorsnortheeditorsnorthepublishercanacceptanylegalresponsibilityfor anyerrorsoromissionsthatmaybemade.Thepublishermakesnowarranty,expressorimplied,with respecttothematerialcontainedherein. Printedonacid-freepaper SpringerispartofSpringerScience+BusinessMedia(www.springer.com) Preface Bioethanol represents one of the most promising biofuels, exhibiting several advantages, such as high octane number, low cetane number high heat of vapor- izationand,mostimportantly,reductionofgreenhousegasemissions.Avarietyof biomass feedstock have been explored for ethanol production including sucrose- rich crops such as sugarcane and sugar beet, starch-rich crops such as maize and grain sorghum, and lignocellulosic materials such as woody biomass, herbaceous perennials, and various wastes. In the United States, the Department of Energy has set a goal of 60 billion gallonsofrenewablefuelsperyeartobeproducedby2030.IntheEuropeanUnion there is a mandatory target to substitute 10 % of transportation fuels with renewable fuels by 2020. Production of ethanol from corn starch in United States hasalmostreacheditsfullcapacity.Moreover,ethanolproductionfromthisedible feedstockposesconcernsaboutcompetitionwithfoodandfeedsupplies.Theonly sustainablealternative substratefor ethanol productionislignocellulosicbiomass. LignocellulosicbiomassesarethemostabundantrenewableresourcesonEarth. The use of lignocellulosic materials for second-generation ethanol production would minimize the conflict between land use for food (and feed) and energy production. Moreover, these raw materials are less expensive and they present a more even geographical distribution than the conventional agricultural feedstock. Alargefractionoflignocellulosesisrepresentedbyresidualbiomasssuchasagro- industrial wastes, agricultural and forest crop residues, and the organic and paper fractions of municipal solid waste that would represent the key response to the needofincreasingrenewableenergyproduction.Itisworthnotingthatonlysmall amounts of cellulose, hemicellulose, and lignin composing agricultural residues are currently exploited, the majority being considered wastes. Moreover, second- generationethanolproductionanduse showlower greenhouse gas emissions than the first-generation fuels, reducing environmental impact, particularly in terms of climate change. Lignocellulose consists of three types of polymers—cellulose, hemicellulose, andlignin-bondedbybothnon-covalentandcovalentcrosslinkages.Celluloseisa highly crystalline linear polymer that is composed of D-glucose units linked by b-1,4 glycosidic bonds. Hemicellulose is also a polysaccharide, accounting for v vi Preface around 25–35 % of dry wood. It is a very heterogeneous and ramified polymer, consistingofamixture ofvarious monosaccharides,suchasxyloseandarabinose (both 5-carbon sugars) and glucose, mannose and galactose (all 6-carbon sugars), and glucuronic acid. Lignin is present in the cellular wall to give structural sup- port, mechanical resistance, impermeability, and defense against microbial attack and oxidative stress. It is an amorphous heteropolymer formed from phenylpro- pane units joined together by non-hydrolyzable linkages. Lignocellulose conversion into ethanol commonly involves i) a pretreatment to remove the barrier of lignin and expose plant cell wall polysaccharides, ii)enzymaticsaccharificationofsugarswitha(hemi)cellulolyticenzymecocktail, and iii) fermentation of the sugars with ethanologenic microorganisms. Pretreat- ment involves the use of acids, alkalis, and/or organic solvents. Numerous pre- treatment strategies have been developed such as physical treatment, chemical treatment (alkaline or acid), biological treatment, physicochemical treatment, i.e., steam explosion, liquid hot water, ammonia fiber expansion, supercritical fluid treatment, and thermochemical treatment. Biological pretreatments are also investigated to reduce use of toxic reagents. After pretreatment, the released cel- lulose and hemicelluloses are hydrolyzed to monomeric sugars (hexoses and pentoses) using acid or enzymatic methods. Enzymatic hydrolysis by (hemi)cel- lulases is the preferred method because of the higher conversion yields and less corrosiveandtoxicconditionscomparedtotheacidhydrolysis.Fermentationofall free sugars into ethanol is carried out by yeasts or bacteria. The cost of enzymes used in the process is considered as one of the key bottlenecks for producing fuels and chemicals from lignocellulosic biomass. Severaleffortsareunderwaytoreducethecostandmaximizeenzymeproduction. Some of the strategies include improving the performance of the enzymes by increasing the specific activity (through direct evolution and site directed muta- genesis) and thereby minimizing enzyme dosage or reduce the cost of enzyme production by improving cellulase titers during fermentation (through process engineering approaches by using cheap substrates including biomass, producing enzymes near biorefinery, or expression of enzyme in plants). The enzymatic hydrolysis may take place in a separate step followed by fer- mentationcalledseparatehydrolysisandfermentationprocess,oritmaytakeplace togetherwiththefermentationinasimultaneoussaccharificationandfermentation of hexoses process or simultaneous saccharification and co-fermentation of both hexoses and pentoses. The ultimate objective is a one-step consolidated biopro- cessing of lignocellulose to bioethanol, in which all the steps occur in a single reactorwhereasinglemicroorganismormicrobialconsortiumconvertspretreated biomass into ethanol without added enzymes. Inthisbook,themaintools,thecurrenttechnologicaldevelopments,andfuture prospects in cellulosic ethanol production and research are described. The editing work of this book was supported by grant from the Ministero dell’Università e della Ricerca Scientifica-Industrial Research Project ‘‘Integrated agro-industrial chains with high energy efficiency for the development of eco- compatible processes of energy and biochemicals production from renewable Preface vii sources and for the land valorization (EnerbioChem)’’ PON01_01966, funded in the frame of Operative National Programme Research and Competitiveness 2007–2013 D. D. Prot. n. 01/Ric. 18.1.2010. Contents 1 Introduction: Potential of Cellulosic Ethanol. . . . . . . . . . . . . . . . . 1 Takashi Watanabe 2 Sources for Lignocellulosic Raw Materials for the Production of Ethanol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Yitzhak Hadar 3 The Pretreatment Step in Lignocellulosic Biomass Conversion: Current Systems and New Biological Systems. . . . . . . . . . . . . . . . 39 Adenise Lorenci Woiciechowski, Luciana Porto de Souza Vandenberghe, Susan Grace Karp, Luiz Alberto Junior Letti, Júlio Cesar de Carvalho, Adriane Bianchi Pedroni Medeiros, Michele Rigon Spier, Vincenza Faraco, Vanete Thomaz Soccol and Carlos Ricardo Soccol 4 The Saccharification Step: Trichoderma Reesei Cellulase Hyper Producer Strains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Venkatesh Balan, Mingjie Jin, Alan Culbertson and Nirmal Uppugundla 5 The Saccharification Step: The Main Enzymatic Components . . . . 93 Marie Couturier and Jean-Guy Berrin 6 Extremophilic (Hemi)cellulolytic Microorganisms and Enzymes. . . 111 Beatrice Cobucci-Ponzano, Elena Ionata, Francesco La Cara, Alessandra Morana, Maria Carmina Ferrara, Luisa Maurelli, Andrea Strazzulli, Rosa Giglio and Marco Moracci ix x Contents 7 The Alcohol Fermentation Step: The Most Common Ethanologenic Microorganisms Among Yeasts, Bacteria and Filamentous Fungi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 Parameswaran Binod, Raveendran Sindhu and Ashok Pandey 8 Other Ethanologenic Microorganisms. . . . . . . . . . . . . . . . . . . . . . 151 Eulogio Castro 9 Consolidated Bioprocessing for Improving Cellulosic Ethanol Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 Antonella Amore, Simona Giacobbe and Vincenza Faraco Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 Chapter 1 Introduction: Potential of Cellulosic Ethanol Takashi Watanabe Abstract Conversion of lignocellulosic biomass is emerging as one of the most important technologies for sustainable production of renewable fuels and chemi- cals due to its widespread availability, large quantity, non-competitiveness with foodsupply,potentialasplatformforgreenchemicals,andhighmitigationeffects on GHG emissions. The process for cellulosic ethanol production by enzymatic saccharification and fermentation consists of pretreatments exposing plant cell wall polysaccharides, production of reducing sugars with a (hemi) cellulolytic enzyme cocktail, and fermentation of the sugars with ethanologenic microorgan- isms. Simultaneous saccharification and co-fermentation (SSCF) and consolidate bioprocess (CBP) have been studied as cost-effective integrated processes for bioethanolproduction.Forthispurpose,ethanologenicmicroorganismshavebeen engineered to co-utilize hexoses and pentoses at a similar rate and secrete or display hydrolases on the cell surfaces. In this chapter, the role of bioethanol in sustainable society, its potential as new platform chemicals, and the current technological developments and future prospects in bioethanol research are overviewed. Contents 1.1 DevelopmentofSustainableSocietyThroughCellulosicFuelEthanol........................ 2 1.2 BioethanolasFeedstockforChemicalIndustry............................................................. 5 1.3 TechnologicalAdvancesandTasksforCellulosicEthanolProduction........................ 7 1.3.1 StrategiestoEnhanceEnzymaticHydrolysisofLignocellulosicBiomass........ 11 1.3.2 GeneticEngineeringofEthanologenicMicroorganismstoImprove FuelEthanolProduction....................................................................................... 13 1.3.3 ConsolidatedBioprocessingforCellulosicBioethanolProduction.................... 15 T.Watanabe(&) ResearchInstituteforSustainableHumanosphere,KyotoUniversity,Gokasho,Uji,Kyoto 611-0011,Japan e-mail:[email protected] V.Faraco(ed.),LignocelluloseConversion, 1 DOI:10.1007/978-3-642-37861-4_1,(cid:2)Springer-VerlagBerlinHeidelberg2013
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