Characterization of neutral xylanases from Chaetomium cellulolyticum and their biobleaching effect on eucalyptus pulp

Chaetomium cellulolyticum produced three xylanases with molecular weights o f 25, 47, and 57 kDa and pIs of 8.9, 8.4, and 5.0, respectively. According to their biochemical characteristics and specificity, the 25- and 47-kDa xy lanases were related to the family of G and the 57-kDa xylanase to the fami ly of F. These xylanases had a neutral pH optimum within the range of 6-7 a nd the 25-kDa xylanase maintained high activity at alkaline pH up to 10. An important characteristic of the 25-kDa xylanase was its high stability at pH 9. Bleaching effects of xylanases from C. cellulolyticum on eucalyptus p ulp were examined. The 25-kDa xylanase had higher than other xylanases isol ated and commercial preparation Ecopulp TX 200 biobleaching activity at pH 9. All of the xylanases exhibited endo-action patterns, slight differences in the ratio of low-molecular weight sugars were detected. Changes in molec ular weight distributions of xylan were observed to be the same for xylanas es from C. cellulolyticum confirming the endo-mode of action of these enzym es. (C) 1999 Elsevier Science Inc. All rights reserved.