Abstract: Preparation of cellulase-poor xylanase by Trichoderma reesei Rut C 30 in batch and fed-batch fermentations and its application on biobleaching were investigated. The xylanase activity, xylanase volumetric productivity and xylanase yield in batch fermentation were 152.09 IU/mL,2 112.4 IU/(L·h) and 10 139.3 IU/g xylan, respectively, when 15 g/L xylan was employed as carbon source. Compared to batch fermentation, xylanase formation in fed-batch culture,in which 17 g/L xylan was employed as carbon source, was more efficient and the xylanase activity, xylanase volumetric productivity and yield were 252.14 IU/mL,3 501.9 IU/(L·h) and 14 831.8 IU/g xylan, respectively. When straw pulp was pretreated with the xylanase-poor xylanase followed by a hypochlorite bleaching, a pulp brightness of 2%-5% (SBD) higher than that of the untreated one under the same hypochlorite dosage could be obtained, or 43% of active chlorine consumption could be saved under the same brightness.

Key words: cellulase-poor xylanase, biobleaching, fed-batch