Isolation, purification and characterization of Xylanases from Aspergillus Sydowii

Abstract

The present study deals with the xylanases from the fungus Aspergillus sydowii SBS 45. The fungus isolated from the soil, produced cellulase-free xylanase under SmF condition. The different conditions optimized for maximum production of xylanase include incubation temperature (30ºC), initial pH of the medium (pH7), incubation time (9days), substrate (birch wood xylan) concentration (0.5 % w/v), nitrogen source (soyabean meal, 0.25 % w/v), metal ions such as Al3+, Ba2+, Mn2+ and Zn2+ (10 ppm), the amino acids such as L-aspartic acid and L-lysine (0.1 % w/v), the vitamin inositol (0.1 % w/v), and the surfactant tween-80 (0.1 % w/v). Two xylanases designated as xylanase I and xylanase II purified from the crude culture filtrate showed remarkable pH activity and stability which are rare among fungal xylanases. The purified xylanases showed high specificity for xylan substrate. The crude xylanase used for pulp bleaching gave promising results. When 10 U/g pulp of xylanase is given, 5kg/ton elemental chlorine and 2 kg/ton H2O2 can be reduced and when 25 U/g pulp of xylanase was given 5kg/ton elemental chlorine and 4 kg/ton H2O2 can be reduced, thereby retaining the pulp brightness at the control level. Perhaps this might be the first report that deals with the purification and application of xylanase from Aspergillus sydowii. So from the results it can be concluded that xylanase from Aspergillus sydowii can be used in pulp and paper industry as a potential enzymatic bleaching agent.