Some mechanisms of cellobiase formation were studied in Aspergillus japonicus 2092 and A. heteromorphus 3010. Formation of cellobiase in both strains was found to be a non-inducible constitutive character. The delay in formation of cellobiase in batch culture with glucose was shown to be determined by catabolic repression. Aspergillus heteromorphus 3010 was more sensitive to catabolic repression than A. japonicus 2092. To remove the effect of glucose repression two modes of fed-batch processes were developed : moderate and intensive. Both modes used the double algorithm of glucose supply based on computer-aided process control. For A. heteromorphus 3010 the moderate fed-batch was optimal, while for A. japonicus 2092 intensive fed-batch was more efficient. These regimes resulted in a three-fold increase in cellobiase in comparison with batch culture and allowed the combination of growth and biosynthesis of the enzyme in one phase.