ABSTRACT
This chapter provides a review of primary cellulolytic enzymes and their respective functions within natural cellulosomes. To use cellulosic material as feedstock for bioethanol production, chipped or ground biomass is typically pretreated to facilitate enzyme access to long-chain carbohydrates, which are the macromolecules that are reduced to fermentable sugar for conversion to ethanol. The carbohydrate-binding modules facilitate interactions between enzymes and their respective carbohydrate substrates. Lignocellulolytic enzymes are categorized as cellulases, hemicellulases, ligninolytic enzymes, and pectinases. Functionally, cellulases may be generally categorized into three groups based on the type of reaction that they catalyze: carbohydrases, oxidative cellulases, and phosphorylases. Several accessory enzymes, including oxidases, are also involved in the breakdown of lignin by increasing the ligninolytic activity of principal enzymes. There are some accessory enzymes and nonenzymatic components known as mediators that increase the ligninolytic activity of primary enzymes.
