Hemicellulases: Diversity and Applications, Chapter 7

The chemical composition and architecture of plant tissue have been optimized for plant survival in a hostile environment, one filled with microbial and animal sources of insult. Plants use complex polymers of arabinose, mannose, glucose, and xylose (known as hemicelluloses) to intertwine with, and thus strengthen and stabilize, homogenous polymers of cellulose. Hemicelluloses also link thepolyphenolic portion of the plant cell in three-dimensional structures, known as lignin-carbohydrate complexes. The non-plant ecosystem has developed enzymes that can efficiently hydrolyze these plant polymers. Hericellulases are a diverse collection of Omicron-glycosyl hydrolases, with more than 25 types of catalytic activity cataloged to date. They may play an inportant role in capturingfermentable sugars from lignocellulosic biomass, especially where processes based on alkaline pretreatments are used. Such pretreatments yield highly digestible cellulose (cellulases) and produce liquid streams rich in extracted lignins and polymeric hemicellulose. This chapter examines the general nature of plant hemicellulose and introduces the types, activities and uses of hemicellulases inbiomass conversion technologies.