In the enzymatic hydrolysis of plant cell walls, cellulose digestion is highly dependent on hemicellulose digestion. Although other factors such as crystallinity and lignin content have been suggested as barriers to the enzymatic attack on lignocellulose (Kong et al. 1993), the key to increasing lignocellulose digestibility depends on the increase of the cellulose surface that is accessible to the enzymes. Hemicellulose surrounds the cellulose fibrils, protecting them from any biological attack. This makes it a necessity to hydrolyze hemicellulose first. It is now thought that digestion of hemicellulose loosens the rigid, complex structures cover­ing the microfibrils of the cell wall and exposes the cellulose surface to cellulase attack (Ding and Himmel 2006) . Indeed, recent studies of the augmentation of cellulase systems with xylanases and carbohydrate esterases demonstrate clearly that cellulose digestibility is linked to a synergistic relationship between these enzymes (Selig et al. 2008).