Modification of Douglas-fir mechanical and kraft pulps by enzyme treatment.

A cellulase enzyme preparation was assessed for its potential to enhance the fiber characteristics of mechanical and kraft pulps derived from Douglas-fir. The effect of enzyme treatment on pulp properties varied with enzyme dosage. A charge of 1 mg protein per gram of ovendry pulp improved handsheet density and smoothness, increased pulp freeness, and reduced fiber coarseness while only slightly diminishing sheet strength properties. In general, fiber-length fractions showed the same resonse to treatment as the unfractionated whole pulp. However, tensile strength for the kraft fiber fractions increased with enzyme treatments, while the whole pulp suffered a slight decline. This suggests the possibility of improving pulp properties by selective treatment of individual fiber fractions. Application: This study examines the potential of using cellulase enzymes to selectively modify pulp fiber characteristics.