BIOBLEACHING EFFECT OF THERMOSTABLE XYLANASE OF T.LANUGINOSUS ON KRAFT PULP

The potential application of the thermostable xylanase was further evaluated in biobleaching of kraft pulp.During biobleaching,the effect of enzyme charge,pH values,chlorine charge was investigated.The brightness of bleached pulps from the xylanase pretreated kraft pulp was 1.06%～5.11% ISO higher than that of the control.The result demonstrated that the crude xylanase preparation was at least as effective in enhancing brightness with concomitant preservation of paper strength properties.Chlorine dioxide consumption was reduced with xylanase-pretreated pulps while still maintaining brightness at the control level.Besides,pretreatment of pulp with the xylanase was also effective at an alkaline pH as high as pH 11.0.Scanning electron microscopy revealed significant surface modification of kraft pulp fibres without marked fibre disruptions.However,the xylanase does have the advantage of being active and stable at 65 ℃ and at neutral to alkaline pH values appropriate for applications in paper pulp processing.