Has endoglucanase activity on substrates containing beta-1,4 glycosidic bonds, like in carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC) and beta-glucan. May be involved in the degradation of complex natural cellulosic substrates. Endohydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans. By cellulose, cellobiose, lactose and sophorose. May also be O-glycosylated. Belongs to the glycosyl hydrolase 61 family.