Total cellulase activity was determined by the filter paper assay procedure (Mandels and Sternberg, 1976). The assay system had a total volume of 2 ml, consisting of 1 ml of crude enzymatic extract, 1 ml of 0.2 M sodium acetate buffer (pH 4.2) and 50 mg of Whatman filter paper N° 1, incubated for 60 min at 50°C. The amount of reducing sugar was measured by the 3,5-dinitrosalicylic (DNS) reagent method according to Miller (1959).