Selection of Heat-Stable Clostridium cellulovorans Cellulases After In Vitro Recombination

Cellulases degrade cellulose, which is the most abundant biological polymer on the earth (1 ). Although the chemical composition of cellulose is very simple, consisting of only glucose residues connected by β-1,4-glycosidic bonds, no single enzyme is able to degrade crystalline cellulose. To degrade crystalline cellulose to glucose, at least three enzymes have to cooperate: endoglucanase (EC 3.2.1.4), exoglucanase (cellobiohydrolase, EC 3.2.1.91), and β-glucosidase (EC 3.2.1.21) (1 ).