THE IMPACT OF XYLANASES ON BLEACHING OF EUCALYPTUS KRAFT PULP

Commercial xylanases, Novozyme 473, VAI Xylanase and Cartazyme HS-10 were evaluated for prebleaching of eucalyptus kraft pulp. Pretreatment with Novozyme 473 and VAI Xylanase resulted in 31% reduction in chlorine consumption at C-stage with corresponding reduction in TOCl. The final brightness and strength properties remained unchanged and the viscosity was higher than that of control. Pretreatment with Cartazyme HS-10 also reduced the chlorine consumption by 31% at C-stage and 30% reduction in TOCl content in the extraction stage effluent. The brightness ceiling was increased by 2.5 points and the strength properties of the pulp were preserved. At constant chemical dose, the improvement in final brightness level was noticed with all three enzymes. Maximum brightening effect was noted with Cartazyme HS-10. Up to 4.9 points increase in brightness was achieved in CEH sequence. The strength properties of the pulps compared very favourably with that of control. With Novozyme 473 and VAI Xylanase about 3 and 2.1 points improvement in brightness level, respectively, was obtained.