Evaluation of the bleach-enhancing effect of xylanases on bagasse pulp

摘要

Until recently enzymatic bleaching of non-woody materials has received scant attention. In this study three commercial xylanases were evaluated in both ECF and TCF bleaching to enhance the bleachability of bagasse soda pulp. The enzyme pretreatment was carried out at various charges under optimized conditions. In both bleaching sequences, Xylanase P (Iogen Corp.) was the most efficient bleach-enhancing enzyme, when compared on an equal enzyme charge on pulp (as U/g) basis. This enzyme was able to improve brightness of DED bleached bagasse pulp by up to 8.2 brightness points or alternatively reduce the consumption of chlorine dioxide by 33%. Ecopulp TX-200C (Roehm Enzyme) and Cartazyme NS-10 (Clariant) were equally efficient in the ECF bleaching of bagasse pulp producing chlorine dioxide savings of 20%. In all instances, however, the biobleaching effect induced due to xylanase pretreatment was dependent on both the enzyme and chlorine dioxide charges used. At similar brightness levels, the TCF biobleaching in sequence X-OqPaP was less efficient than the ECF DED biobleaching. Mechanical pretreatment of the pulp prior to the ECF biobleaching slightly increased final brightness, indicating "activation" of pulp to facilitate enzyme and chemical bleaching. Xylanase pretreatment had an insignificant effect on the physical properties of the ECF bleached pulp.