indicating that further strain improvement is necessary to further enhance the enzymatic hydrolysis performances of T. viride EU2-77 cellulases. Among the entire enzyme samples prepared, the mixture of commercial enzymes Celluclast 1.5 L and Novozym 188 and Cellic CTec alone were the most efficient in reducing sugar production and cellobiose hydrolysis.
Nevertheless, mutant EU2-77 demonstrated a much comparable hydrolysis performances with the above two enzyme samples however with a slightly lower initial hydrolysis rate. This implies that longer period is necessary for lignocellulosic biomass hydrolysis using enzymes from mutant EU2-77. Although mutant strain T. viride EU2-77 could not completely hydrolyze the cellobiose, end product inhibition was not significant as its reducing sugar and glucose yields were much comparable to the best performers, Cellic CTec alone and the mixture of Celluclast 1.5 L and Novozyme 188.
It was worthwhile noting that the activity ratio of β-glucosidase/FPase for mutant EU2-77 was 1.84 (2.19 IU/ml FPase and 4.04 β-glucosidase, Table 1). This was much smaller than those obtained from mutant strains of both T. atroviride (28) and T. citrinoviride (29), each of which demonstrated such enzyme activity ratio of around 10 or above. However the hydrolysis efficiency of crude enzyme mixture from mutant EU2-77 was very much consistent with those obtained
from the above mentioned mutant strains of Trichoderma sp. (28,29). Such result indicates that very high β-glucosidase activity does not increase the hydrolytic capacity and the overall FPase any further, as reported by Kovács et al. (28).