Cellulase assay methods: a review

Abstract

The measurement of cellulase activity must be approached using somewhat unconventional techniques. Whereas most enzyme theory is based on reactions in solutions, the cellulase-cellulose system involves an interface between the enzymes (either free in solution or bound to cell surfaces) and an insoluble, heterogenous substrate surface. Microbial hydrolysis of native crystalline cellulose normally requires the concerted action of a group of enzymes, a cellulase complex. Assessing the contributing activities of the components of this complex is difficult, since they often aggregate physically, and their differences in substrate specificity are relative, not absolute. Most of the component enzymes attack fl-l,4-glucosidic linkages, and differ only in efficiency, which is dependent on the chemical environment surrounding the linkage. In addition, synergistic interactions between the various components of a cellulase complex further complicate their individual assessment. For example, certain components may be important to the functioning of the complex as a whole and yet have no detectable activity against crystalline cellulose when studied in isolation. It also now appears that there are significant differences between the modes of action of cellulase complexes from various organisms, particularly between procaryotes and eucaryotes. The situation is further complicated by considerable uncertainty regarding the structures of the various forms of cellulose employed as substrates.