THE ROLE OF TRICHODERMA-REESEI XYLANASE AND MANNANASE IN THE TREATMENT OF SOFTWOOD KRAFT PULP PRIOR TO BLEACHING

Xylanase treatment improved the bleachability of softwood kraft pulp b oth in conventional chlorine bleaching and in peroxide delignification . The mannanase isolated from Trichoderma reesei acted differently and improved the bleachability in the peroxide delignification significan tly more than in the chlorine bleaching. When mannanase and xylanase w ere dosed together a positive effect was detected in both bleaching se quences. The reason for the different efficiencies of these enzymatic treatments in the bleaching may be the selectivities of the bleaching chemicals. The mannanase could hydrolyze amounts of glucomannan compar able to the xylan hydrolyzed by xylanase, suggesting that at least par t of both hemicelluloses are located on the surface of the fibres.