Bleaching of wheat straw-rich soda pulp with xylanase from a thermoalkalophilic Streptomyces cyaneus SN32

An alkalistable endoxylanase from Streptomyces cyaneus SN32 was applied in bleaching of wheat straw enriched soda pulp. The xylanase dose of 10 IUg(-1) moisture free pulp exhibited maximum bleach boosting of soda pulp (pH 9.5-10.0) optimally at 65 degrees C after 2 h of reaction time. Pre-treatment of pulp with xylanase and its subsequent treatment with 6% hypochlorite reduced the kappa number by 8.7%, enhanced the brightness index by 3.56% and improved other paper properties such as tear index and burst index. The enzymatically-prebleached pulp when treated with 10% reduced level of hypochlorite (5.4%) gave comparable brightness of resultant hand sheets to the fully bleached pulp (6% hypochlorite).