Purification and characterization of xylanase from Aspergillus ficuum AF-98.

The purification and characterization of xylanase from Aspergillus ficuum AF-98 were investigated in this work. The extracellular xylanase from this fungal was purified 32.6-fold to homogeneity throughout the precipitation with 50-80% (NH(4))(2)SO(4), DEAE-Sephadex A-50 ion exchange chromatography and Sephadex G-100 chromatography. The purified xylanase (specific activity at 288.7 U/ mg protein) was a monomeric protein with a molecular mass of 35.0 kDa as determined by SDS-PAGE. The optimal temperature and pH for the action of the enzyme were at 45 degrees C and 5.0, respectively. The xylanase was activated by Cu(2+) up to 115.8% of activity, and was strongly inhibited by Hg(2+), Pb(2+) up to 52.8% and 89%, respectively. The xylanase exhibited K(m) and V(max) values of 3.267 mg/mL, 18.38 M/min/mg for beechwood xylan and 3.747 mg/mL, 11.1M/min/mg for birchwood xylan, respectively.