In our study, the culture broth from T. reesei Rut-C30 and the commercial cellulase, Celluclast 1.5 L, produced high levels of cellobiose during the hydrolysis of waste newspaper, owing to the deficiency of extracellular β-glucosidase (0.21 IU/ml) (32). The reason for the low secretion of this enzyme into the fermentation broth of T.reesei is that the major part of the β-glucosidase is tightly bound to the cell walls of the fungus during cultivation and some part of the enzyme may be found inside the cells (33). Regardless of this fact, the majority of researchers and industrial companies prefer this particular species for cellulase production. Due to the higher amount of extracellular β-glucosidase produced, supernatants of our new T.viride mutant EU2-77 hydrolysed the waste newspaper more efficiently than that of T. reesei. For T. reesei supernatants and for Celluclast 1.5 L, β-glucosidase supplementation was necessary in order to achieve high sugar yields. Similar fermentation and hydrolysis results were obtained with Acremonium cellulolyticus (10), T. atroviride (28), T. citrinoviride (29), and T. harzianum E58 (34). Mutant strain EU2-77 produced higher levels of extracellular β-glucosidase than T. reesei Rut-C30, and therefore proved to be more efficient to break down various lignocellulosic substrates into glucose molecules.