Abstract
Douglas-fir heartwood thermomechanical pulp was treated with laccase enzymes at 25 and 50°C with and without added oxygen. The treated pulps were cleached with hudrogen peroxide at increasing alkali charges. Laccase treatments without added oxygen increased bleached brightness by 1.5-2.5 pts ISO, and decreased hydrogen peroxide consumption by 15-20%. The enzyme treatments were not enhanced when supplemented with oxygen. When the effectiveness of four different laccase enzymes was compared for the treatment of Douglas-fir heartwood thermomechanical pulp, there were no significant differences found in the performance among the enzymes. Possible explanations for the observed results are given.,Peer reviewed,Published.