There are a number of forms of cellulose that are used toassay cellulases; carboxymethylcellulose (CMC) is asoluble form that is an excellent substrate for endocellulases and its hydrolysis does not require a CBM. Amorphous cellulose, which is produced by concentrated acidtreatment of crystalline cellulose is a good substrate formost cellulases and its hydrolysis is usually not affectedby the CBM. Crystalline cellulose (Avicel, bacterial cellulose or filter paper), which is the main form of cellulosein most plant cell walls, requires a CBM for effectivehydrolysis