The conditions of hydrolysis of 'skop' (short fiber waste material from the paper industry) and cellolignin (waste of industrial furfural production) by the cellulase system from Penicillium sp. in a batch reactor have been evaluated The optimal conditions were: enzyme (filter paper activity) - 1.7 U/ml, skop - 100 g/l, cellolignin - 150 g/l, pH 4.5, temperature 50 degrees C. Agitation was essential for cellolignin but not essential for skop hydrolysis. Studies of fed-batch process of saccharification of both substrates by three cellulase preparations (from Penicillium sp., Trichoderma reesei and combined preparations of T. reesei and Aspergillus foetidus) have shown that the highest saccharification activity was demonstrated by Penicillium cellulase. Penicillium cellulase was able to hydrolyze, during 48 h, three portions of skop or cellolignin with a degree of cellulose conversion to glucose of 68-84% and final glucose concentrations of 93-98 g/l. The use of fed-batch saccharification decreased consumption of enzyme and increased the final glucose concentration compared to batch hydrolysis. The role of different factors in decreased rate of skop and cellolignin hydrolysis by Penicillium cellulase in the course of reaction has been evaluated. The main factors influencing the efficiency of saccharification were decrease of skop and cellolignin reactivity during hydrolysis and inhibition of enzymes by glucose and cellobiose.