Characterization of the activity profile in cellulases derived from recombinant strains of Trichoderma reesei

Enzyme preparations from eight deletion strains ofTrichoderma reesei were characterized with regard to their activity profile against several model substrates, and subsequently compared to the complete cellulase system of the industrial preparation Celluclast 1.5L (Novozymes, Denmark). The recombinant enzymes (Röhm Enzyme Finland Oy, Finland) comprised of 4 single (A, CBH I-; B, CBH II-; C, EG I-; D, EG II-), 2 double- ( E, CBH I/II-, F, EG I/II-) and 2 trideletion (G, EG II-/CBH I/II-; H, CBH II-/EG I/II-) enzymes. Compared to Celluclast 1.5L, deletion of both genes encoding for EG I and EG II (enzyme F) resulted in very little endoglucanase activity in the enzyme preparation, whereas the absence of both CBH I and CBH II (enzyme E) reduced filter paper activity by more than 75%. In general, for saccharification experiments in which less than 2% of the substrate was hydrolyzed to soluble sugars, EG-rich preparations (enzyme E at 200 mg/g) caused a considerable decrease in the degree of depolymerization (DP) of substrates with high amorphous character (e.g., filter paper fibers), whereas cellulose DP was not affected when substrates having a higher supramolecular organization were used (e.g., Avicel, Sigmacell or cotton fibers). By contrast, when CBH-rich preparations (enzyme F, 200 mg/g) were used, greater cellulose saccharification yields were observed (14%), and changes in cellulose DP were primarily due to the progressive removal of cellobiose residues from the termini of cellulose molecules.