Cellulose is a long chain of polyglycans linked by P(1^-4)-glycosidic linkages. The synergetic action of cellulase consists of endoglucanase, exoglucanase (cellobiohydrolases) and p-glucosidase (cellobiase) acting together to depolymerize cellulose into glucose molecules with liberated water molecules. The hydrolysis of cellulose involves three different synergetic stages. The following steps are summarized:

• Endoglucanase hydrolyzes inner polyglucan molecules linkages into small polysaccharides chain.

• Exoglucanase (CBHI and CBHII) remove the terminal disaccharide glucan units of cellulose.

• CBHI degrades terminal of cellulose polymer.

• CBHII releases cellobiose units from the endoglucanase degraded

cellulose.

• p-glucosidase hydrolyzes cellobiose units into glucose.

P-glucosidase prevents feedback substrate inhibition of endo — and exgo — glucanases by hydrolyzing cellobiose molecules into glucose. The maximum enzymatic hydrolysis rates using cellulase mixtures are generally carried out at 50 ± 5°C between pH 4.8 and 5.5 (Galbe and Zacchi 2002). Other factors that govern the hydrolysis of cellulose include lignin content, crystallinity, hemicellulose content, particle size and surface area of lignocellulosic biomass (Sun and Cheng 2002; Pan 2008; Zhu et al. 2008; Hendriks and Zeeman 2009; Harmsen et al. 2010).