Aqueous Pretreatment of Plant Biomass for Biological and Chemical Conversion to Fuels and Chemicals -- Contents -- List of Contributors -- Foreword -- Series Preface -- Preface -- Acknowledgements -- 1 Introduction -- 1.1 Cellulosic Biomass: What and Why? -- 1.2 Aqueous Processing of Cellulosic Biomass into Organic Fuels and Chemicals -- 1.3 Attributes for Successful Pretreatment -- 1.4 Pretreatment Options -- 1.5 Possible Blind Spots in the Historic Pretreatment Paradigm -- 1.6 Other Distinguishing Features of Pretreatment Technologies -- 1.7 Book Approach -- 1.8 Overview of Book Chapters -- Acknowledgements -- References -- 2 Cellulosic Biofuels: Importance, Recalcitrance, and Pretreatment -- 2.1 Our Place in History -- 2.2 The Need for Energy from Biomass -- 2.3 The Importance of Cellulosic Biomass -- 2.4 Potential Barriers -- 2.5 Biological and Thermochemical Approaches to the Recalcitrance Barrier -- 2.6 Pretreatment -- Acknowledgements -- References -- 3 Plant Cell Walls: Basics of Structure, Chemistry, Accessibility and the Influence on Conversion -- 3.1 Introduction -- 3.2 Biomass Diversity Leads to Variability in Cell-wall Structure and Composition -- 3.3 Processing Options for Accessing the Energy in the Lignocellulosic Matrix -- 3.4 Plant Tissue and Cell Types Respond Differently to Biomass Conversion -- 3.5 The Basics of Plant Cell-wall Structure -- 3.6 Cell-wall Surfaces and Multilamellar Architecture -- 3.7 Cell-wall Ultrastructure and Nanoporosity -- 3.8 Computer Simulation in Understanding Biomass Recalcitrance -- 3.8.1 What Can We Learn from Molecular Simulation? -- 3.8.2 Simulations of Lignin -- 3.8.3 Simulations of Cellulose -- 3.8.4 Simulation of Lignocellulosic Biomass -- 3.8.5 Outlook for Biomass Simulations -- 3.9 Summary -- Acknowledgements -- References.

4 Biological Conversion of Plants to Fuels and Chemicals and the Effects of Inhibitors -- 4.1 Introduction -- 4.2 Overview of Biological Conversion -- 4.3 Enzyme and Ethanol Fermentation Inhibitors Released during Pretreatment and/or Enzyme Hydrolysis -- 4.3.1 Enzyme Inhibitors Derived from Plant Cell-wall Constituents (Lignin, Soluble Phenolics, and Hemicellulose) -- 4.3.2 Effect of Furfurals and Acetic Acid as Inhibitors of Ethanol Fermentations -- 4.4 Hydrolysis of Pentose Sugar Oligomers Using Solid-acid Catalysts -- 4.4.1 Application of Solid-acid Catalysts for Hydrolysis of Sugar Oligomers Derived from Lignocelluloses -- 4.4.2 Factors Affecting Efficiency of Solid-acid-catalyzed Hydrolysis -- 4.5 Conclusions -- Acknowledgements -- References -- 5 Catalytic Strategies for Converting Lignocellulosic Carbohydrates to Fuels and Chemicals -- 5.1 Introduction -- 5.2 Biomass Conversion Strategies -- 5.3 Criteria for Fuels and Chemicals -- 5.3.1 General Considerations in the Production of Fuels and Fuel Additives -- 5.3.2 Consideration for Specialty Chemicals -- 5.4 Primary Feedstocks and Platforms -- 5.4.1 Cellulose -- 5.4.2 Hemicellulose -- 5.5 Sugar Conversion and Key Intermediates -- 5.5.1 Sugar Oxidation -- 5.5.2 Sugar Reduction (Polyol Production) -- 5.5.3 Sugar Dehydration (Furan Production) -- 5.6 Conclusions -- Acknowledgements -- References -- 6 Fundamentals of Biomass Pretreatment at Low pH -- 6.1 Introduction -- 6.2 Effects of Low pH on Biomass Solids -- 6.2.1 Cellulose -- 6.2.2 Hemicellulose -- 6.2.3 Lignin -- 6.2.4 Ash -- 6.2.5 Ultrastructure -- 6.2.6 Summary of Effects of Low pH on Biomass Solids -- 6.3 Pretreatment in Support of Biological Conversion -- 6.3.1 Hydrolysis of Cellulose to Fermentable Glucose -- 6.3.2 Pretreatment for Improved Enzymatic Digestibility.

6.3.3 Pretreatment for Improved Enzymatic Digestibility and Hemicellulose Sugar Recovery -- 6.4 Low-pH Hydrolysis of Cellulose and Hemicellulose -- 6.4.1 Furfural -- 6.4.2 Levulinic Acid -- 6.4.3 Drop-in Hydrocarbons -- 6.5 Models of Low-pH Biomass Reactions -- 6.5.1 Cellulose Hydrolysis -- 6.5.2 Hemicellulose Hydrolysis -- 6.5.3 Summary of Kinetic Models -- 6.6 Conclusions -- Acknowledgements -- References -- 7 Fundamentals of Aqueous Pretreatment of Biomass -- 7.1 Introduction -- 7.2 Self-ionization of Water Catalyzes Plant Cell-wall Depolymerization -- 7.3 Products from the Hydrolysis of the Plant Cell Wall Contribute to Further Depolymerization -- 7.4 Mechanisms of Aqueous Pretreatment -- 7.4.1 Hemicellulose -- 7.4.2 Lignin -- 7.4.3 Cellulose -- 7.5 Impact of Aqueous Pretreatment on Cellulose Digestibility -- 7.6 Practical Applications of Liquid Hot Water Pretreatment -- 7.7 Conclusions -- References -- 8 Fundamentals of Biomass Pretreatment at High pH -- 8.1 Introduction -- 8.2 Chemical Effects of Alkaline Pretreatments on Biomass Composition -- 8.2.1 Non-oxidative Delignification -- 8.2.2 Non-oxidative Sugar Degradation -- 8.2.3 Oxidative Delignification -- 8.2.4 Oxidative Sugar Degradation -- 8.3 Ammonia Pretreatments -- 8.4 Sodium Hydroxide Pretreatments -- 8.5 Alkaline Wet Oxidation -- 8.6 Lime Pretreatment -- 8.7 Pretreatment Severity -- 8.8 Pretreatment Selectivity -- 8.9 Concluding Remarks -- References -- 9 Primer on Ammonia Fiber Expansion Pretreatment -- 9.1 Historical Perspective of Ammonia-based Pretreatments -- 9.2 Overview of AFEX and its Physicochemical Impacts -- 9.3 Enzymatic and Microbial Activity on AFEX-treated Biomass -- 9.3.1 Impact of AFEX Pretreatment on Cellulase Binding to Biomass -- 9.3.2 Enzymatic Digestibility of AFEX-treated Biomass -- 9.3.3 Microbial Fermentability of AFEX-treated Biomass.

9.4 Transgenic Plants and AFEX Pretreatment -- 9.5 Recent Research Developments on AFEX Strategies and Reactor Configurations -- 9.5.1 Non-extractive AFEX Systems -- 9.5.2 Extractive AFEX Systems -- 9.5.3 Fluidized Gaseous AFEX Systems -- 9.6 Perspectives on AFEX Commercialization -- 9.6.1 AFEX Pretreatment Commercialization in Cellulosic Biorefineries -- 9.6.2 Novel Value-added Products from AFEX-related Processes -- 9.6.3 AFEX-centric Regional Biomass Processing Depot -- 9.7 Environmental and Life-cycle Analyses for AFEX-centric Processes -- 9.8 Conclusions -- Acknowledgements -- References -- 10 Fundamentals of Biomass Pretreatment by Fractionation -- 10.1 Introduction -- 10.2 Organosolv Pretreatment -- 10.2.1 Organosolv Pulping -- 10.2.2 Overview of Organosolv Pretreatment -- 10.2.3 Solvents and Catalysts for Organosolv Pretreatment -- 10.2.4 Fractionation of Biomass during Organosolv Pretreatment -- 10.3 Nature of Organosolv Lignin and Chemistry of Organosolv Delignification -- 10.3.1 Composition and Structure of Organosolv Lignin -- 10.3.2 Mechanisms of Organosolv Delignification -- 10.3.3 Commercial Applications of Organosolv Lignin -- 10.4 Structural and Compositional Characteristics of Cellulose -- 10.5 Co-products of Biomass Fractionation by Organosolv Pretreatment -- 10.5.1 Hemicellulose -- 10.5.2 Furfural -- 10.5.3 Hydroxymethylfurfural (HMF) -- 10.5.4 Levulinic Acid -- 10.5.5 Acetic Acid -- 10.6 Conclusions and Recommendations -- Acknowledgements -- References -- 11 Ionic Liquid Pretreatment: Mechanism, Performance, and Challenges -- 11.1 Introduction -- 11.2 Ionic Liquid Pretreatment: Mechanism -- 11.2.1 IL Polarity and Kamlet-Taft Parameters -- 11.2.2 Interactions between ILs and Cellulose -- 11.2.3 Interactions between ILs and Lignin -- 11.3 Ionic Liquid Biomass Pretreatment: Enzymatic Route -- 11.3.1 Grasses.

11.3.2 Agricultural Residues -- 11.3.3 Woody Biomass -- 11.4 Ionic Liquid Pretreatment: Catalytic Route -- 11.4.1 Acid-catalyzed Hydrolysis -- 11.4.2 Metal-catalyzed Hydrolysis -- 11.5 Factors Impacting Scalability and Cost of Ionic Liquid Pretreatment -- 11.6 Concluding Remarks -- Acknowledgements -- References -- 12 Comparative Performance of Leading Pretreatment Technologies for Biological Conversion of Corn Stover, PoplarWood, and Switchgrass to Sugars -- 12.1 Introduction -- 12.2 Materials and Methods -- 12.2.1 Feedstocks -- 12.2.2 Enzymes -- 12.2.3 CAFI Pretreatments -- 12.2.4 Material Balances -- 12.2.5 Free Sugars and Extraction -- 12.3 Yields of Xylose and Glucose from Pretreatment and Enzymatic Hydrolysis -- 12.3.1 Yields from Corn Stover -- 12.3.2 Yields from Standard Poplar -- 12.3.3 Yields from Dacotah Switchgrass -- 12.4 Impact of Changes in Biomass Sources -- 12.5 Compositions of Solids Following CAFI Pretreatments -- 12.5.1 Composition of Pretreated Corn Stover Solids -- 12.5.2 Composition of Pretreated Switchgrass Solids -- 12.5.3 Composition of Pretreated Poplar Solids -- 12.5.4 Overall Trends in Composition of Pretreated Biomass Solids and Impact on Enzymatic Hydrolysis -- 12.6 Pretreatment Conditions to Maximize Total Glucose Plus Xylose Yields -- 12.7 Implications of the CAFI Results -- 12.8 Closing Thoughts -- Acknowledgements -- References -- 13 Effects of Enzyme Formulation and Loadings on Conversion of Biomass Pretreated by Leading Technologies -- 13.1 Introduction -- 13.2 Synergism among Cellulolytic Enzymes -- 13.3 Hemicellulose Structure and Hemicellulolytic Enzymes -- 13.4 Substrate Characteristics and Enzymatic Hydrolysis -- 13.5 Xylanase Supplementation for Different Pretreated Biomass and Effect of β-Xylosidase -- 13.6 Effect of β-Glucosidase Supplementation -- 13.7 Effect of Pectinase Addition.

13.8 Effect of Feruloyl Esterase and Acetyl Xylan Esterase Addition.