EVALUATION OF THE EFFECTS OF HEMICELLULASES ON THE BLEACHABILITY OF SULFITE PULPS

Sulphite pulps were prepared from spruce chips with four cooking metho ds, differing in cooking pH, the use of additives such as anthraquinon e, and the cooking time and temperature. Considerable differences in c arbohydrate composition, Lignin content and yield of the pulps were ob served. The sulphite pulps were treated with Trichoderma reesei xylana ses and mannanase prior to peroxide bleaching. The accessibility of xy lan and glucomannan was greatly dependent on the cooking method used. The xylan was most accessible in the alkaline pulp, whereas glucomanna n was most readily hydrolyzed in the two-stage sodium sulphite pulp. D espite enzymatic hydrolysis of pulp xylan or glucomannan, no clear imp rovement in the bleachability was observed in peroxide bleaching.