Trent Chunzhong Yang1, Jyothi Kumaran2,3, Samuel Amartey4,
Miranda Maki5, Xiangling Li1,6, Fan Lu7, Wensheng Qin5’*
1Aquatic and Crop Resource Development, National Research Council Canada, Ottawa, ON, Canada, 2Human Health
Therapeutics, National Research Council Canada, Ottawa, ON, Canada, 3School of Environmental Sciences, University
of Guelph, Guelph, ON, Canada, ^Division of Biology, Imperial College of Science, Technology and Medicine, South
Kensington, London, UK, ^Department of Biology, Lakehead University, ON, Canada,

6College of Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, China,

7College of Bioengineering, Hubei University of Technology, Wuhan, Hubei Province, China
*Corresponding author email: wqin@Lakeheadu. ca

OUTLINE

Lignocellulosic Biomass and its Pretreatment 72

Nonbiological Pretreatment 72

Physical Pretreatments 72

Chemical Pretreatments 72

Physicochemical Pretreatments 72

Biological Pretreatment with Microorganisms 73

Potential Advantages over Nonbiological

Pretreatment 73

Biological Degradation of Lignin 73

Commonly used Microorganisms for Biological

Pretreatment 73

Natural Microorganisms and Practical Applications in Bioconversion 74

Application of White-Rot Fungus in Treatment of Different Biomasses 74

White-Rot Fungus Pretreatment of Biomass

for Animal Feed 75

White-Rot Fungus Pretreatment in Biological

Pulping 75

White-Rot Fungus Pretreatment of Biomass

for Biofiber 75

Brown-Rot Fungi 75

Soft-Rot Fungi 76

Bacteria 77

Genetically Modified Microorganisms for Biomass Conversion 77

Rational Engineering 77

Metabolic Engineering of Microbial Pathways

for Enhanced Bioproduct Production 78

Strategies of Using Microbial Pretreatment to Enhance Sugar Release for Biofuel and Bioproduct Production 79

Application of Microbial Pretreatment for Biogas Production 80

Application of Microbial Pretreatment for Biomass Conversion 81

Strategies for Microorganism Application

in Biomass 81

Commonly Used Microorganisms in Biomass

Conversion and Some Application Examples 82 Other Bioproducts Produced by Microbial Conversion of Biomass: Introduction 84

References 87

Bioenergy Research: Advances and Applications http://dx. doi. org/10.1016/B978-0-444-59561-4.00005-X

LIGNOCELLULOSIC BIOMASS AND ITS
PRETREATMENT

Lignocellulose is the primary building block of plant cell walls and is composed mainly of cellulose, hemicel — luloses, lignin and small quantities of pectin, proteins, extractives and ash. The cellulose, hemicelluloses and lignin are present in varying amounts in the different parts of the plant and are intimately associated to form the complex structural framework of the plant cell wall where cellulose and hemicellulose are bound together with lignin and other components to form a tight matrix. The composition of lignocellulose depends on plant species as well as growth conditions and age.

Lignocellulose biomass is a renewable, sustainable, abundant and cheap resource for producing renewable biofuels and bioproducts. However, their conversion into fermentable sugar before fermentation is a major hurdle due to its complex structure and recalcitrant nature. While hydrolysis of cellulose and hemicellulose yields fermentable sugars, they are not easily accessible due to the crystalline structure of cellulose and interfer­ence by the phenyl-propanoid polymer, lignin.

Bioconversion of carbohydrates from lignocellulosic feedstocks into fermentable sugars is a key challenge in the biorefinery process. Efficient, cost-effective and environmentally benign pretreatment and hydrolysis methods are required. The primary purpose of pretreat­ment is to change the architecture of the cell wall by delignification and disrupting the cellulose structure and making the lignocellulosic biomass accessible and reactive to allow high rates and yields on enzymatic hydrolysis. Pretreatment has been considered as one of the most expensive processing steps in biomass to fermentable sugar conversion (Mosier et al., 2005).

This article focuses mainly on biological conversion of biomass with microorganisms. However, nonbiolog­ical pretreatments, as well as the most frequently stud­ied and applied procedures, will also be discussed.