Materials and methods Substrate preparationThe substrate (rice straw) was prepared by oven drying (55 °C, 48 h) and grinding to pass through a screen (1 mm). Organic matter and crude protein were analyzed according to the AOAC (8), and fiber fractions were determined following methods described by Van Soest et al. (9). Five hundred milligrams of substrate were used as the sample. Enzymes and dosesThe enzyme products were characterized for the activity of cellulase (CE; E.C.