Shows enzymatic activity towards crystalline cellulose. At long reaction times. It is also able to degrade carboxymethyl cellulose and barley B-glucan. Hydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose and cellotetraose, releasing cellobiose from the non-reducing ends of the chains. Belongs to the glycosyl hydrolase 6 (cellulase B) family.