Abstract: Complex cellulase named Celluclast 1.5L and endo-cellulase named Novozym 476 were applied to hydrolyze the bleached softwood fiber. In the present study, the influences of these two kinds of cellulases on the degree of polymerization (DP) and crystallinity of cellulose were investigated. The results indicated that the DP of cellulose decreased gradually with the increase of the enzyme dosage after hydrolyzed by both cellulases. While the dosage of Celluclast 1.5 L was 3.0 FPU/g, the yield of cellulose was 94.34%. The DP of cellulose decreased to 862 and decreased by 25.95% compared with the control sample (1 164). While the Novozym 476 was in the dosage of 50.0 U/g, the cellulose yield was 94.93%. The DP of cellulose decreased to 711 and decreased by 38.92% compared with the control sample. This showed that in the circumstances of same yield, the cellulose hydrolyzed by Novozym 476 had a lower DP compared with the cellulose hydrolyzed by Celluclast 1.5 L. It meant that endoglucanase was the main factor which led to the decline of DP. With the increase of enzyme dosage of Celluclast 1.5 L, cellulose crystallinity took the changes of M-type, in other words, increased first and then reduced, and finally increased and reduced again. With the increase of enzyme dosage of Novozym 476, the cellulose crystallinity decreased first, and then increased and decreased again.

Key words: cellulase, bleached softwood fiber, hydrolysis, degree of polymerization, crystallinity degree