Modes of Action of Exo- and Endo-Cellulases in the Degradation of Celluloses I and II1

Cotton and Valonia-cellulose (cellulose I) were readily attacked by endo-cellulase of a highly endowise-hydrolysis type, with a sharp decrease in the degree of polymerization, while the simultaneous production of reducing sugar was low. In contrast, viscose rayon and alkali-cellulose (cellulose II) showed little lowering of the degree of polymerization by endo-cellulase, though the effect was slightly greater than with an exo-cellulase, while the simultaneous production of reducing sugar was very high. The synergistic effect of exo- and endo-cellulases on the hydrolysis of cellulose was much higher with cellulose I than with cellulose II. These results can be explained in terms of differences in the polarity of cellulose chains and in the crystallinity and/or ultrastructure of the cellulose fibers.