Prebleaching of kraft pulps with xylanase enzyme for paper manufacture

Wood and agricultural residues, containing cellulose, hemicellulose and lignin as three main polymers, are used in paper manufacture. Removal of lignin from these raw materials by chlorine-based bleaching agents generates dioxins and other toxic chlorinated organic compounds. Prebleaching of Kraft pulps with xylanase enzyme decreases the consumption of chlorine and thereby results in lowered generation of these environmental pollutants. The fungus, Melanocarpus albomyces, seems to be an effective source of xylanase enzyme for prebleaching of pulps, as it produces thermostable xylanases along with xylosidase and xylan-debranching enzymes. Application of the enzyme resulted in 15% chlorine savings for Kraft pulp based on eucalyptus plus bamboo, and improved the brightness of the pulp by 3 percentage points to 83% ISO. The enzyme was less effective against bagasse-based Kraft pulp.