Purification and characterization of xylanases from white-rot fungus Trametes gallica.

The white-rot fungus Trametes gallica was cultivated on wheat straw powder.Following protein precipitation with (NH4)2SO4,the fractions showing xylanase activity were separated and purified by chromatographic analyses with Phenyl-Sepharose CL-4B,DEAE Sepharose FF and Sephadex G-150.The recovery rate and purification fold reached up to 1.45% and 15.6-fold,respectively.The enzymes were further recovered by native-PAGE and three isoenzyme xylanases (XⅠ,XⅡ and XⅢ) of SDS-PAGE purity were finally obtained.The three components had similar molecular weights (approximately 19.0kDa),but exhibited different isolectric points (5.6 for XⅠ ,4.7 for XⅠ and 4.0 for XⅠ ) and carbohydrate content (0.25% for XⅠ ,0.63% for XⅠ and 3.4% for XⅠ ).X Ⅰ can degrade both xylan and cellulose,while XⅠ and X Ⅰ can only degrade xylan.The optimal temperature and pH for XⅠ were 45Ⅱ and 5.0,respectively.Its activity was increased by Mg2+ and Fe2+,while inhibited by Mn2+ and Co2+.Its Km and Vmax were 0.75mg/mL and 5,000mmoL/min·mg,respectively.