Glycoside hydrolase that rapidly hydrolyzes short-chain cellodextrins to yield either cellobiose or cellobiose and glucose as end products; cellobiose is not hydrolyzed further. Also shows limited activity against endoglucanase specific substrates (carboxymethylcellulose (CMC), lichenan, laminarin and xylan). Endohydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans. Is not inhibited by methylcellulose. Belongs to the glycosyl hydrolase 9 (cellulase E) family.