Clostidium stercorarium xylanase A (XynA) composed of a family 11 catalytic domain of glycosyl hydrolases and family VI CBDs bound to amorphous cellulose, i.e., acid-swollen cellulose (ASC), but not highly crystalline cellulose, and it was released from the cellulose protein complex by wash with a cellobiose solution. The Ka and [PC](max) values of ASC were 0.25 liter/mu mol and 26 mu mol/g.