Enzymatic hydrolysis usually follows after preceding pretreatment methods (e.g. steam explosion orDA). During this process, enzymes such as cellulases are utilized to catalyse the break-down of thesolid recalcitrant cellulose stream to liberate glucose monomers for further down-streamfermentation. Cellulases can be produced from genetically engineered microorganisms such asTrichoderma reesei, which can be produced on-site at bio-refineries, such as those used for bioethanolproduction or bought off-site (Humbird, et al., 2011). Cellulases can further be divided into 3 maintypes