The production of cellulases and hemicellulases was studied with T. reesei Rut C-30. This organism produced, together with high cellulase activities, considerable amounts of xylanases and .beta.-glucosidase. Three cellulose concentrations (1, 2.5 and 5.0%) were examined to determine the maximum levels of cellulase activity obtainable in submerged culture. Temperature and pH profiling was used to increase cell mass to maximum levels within 2 days and thereby enhancing fermentor productivity at higher substrate levels. The effect of temperature, pH, Tween-80 concentration, carbon source and substrate concentration on the ratio of mycelial growth and extracellulose enzyme production are described.