Abstract:
The thermo-alkali-stable xylanase from Myceliophthora thermophila BF1-7 was purified and
characterized. The enzyme was purified using a procedure including ammonium sulfate
precipitation, gel filtration and ion exchange chromatographies. The xylanase was purified
to 77.1-fold apparent homogeneity with a recovery yield of 7.48% and maximum specificity
was obtained as 2.31 U mg 1 protein. The purified xylanase appeared as a single protein
band on sodium dodecyl sulfate polyacrylamide gel electrophoresis with a molecular mass
of approximately 14 kDa. Xylanase was most active at pH 12.0 and retained 55% of the
original activity in the pH range of 9.0e12.0 after incubation at 4 C for 24 h. The optimal
temperature of the xylanase was 50 C and it retained more than 77% and 56% of its original
activity after heating at 50 C for 30 and 60 min, respectively. Xylanase was inhibited by
Hg2+ and stimulated by Mg2+, Cu2+, Ag+, Zn2+, ethylenediaminetetraacetic acid (EDTA) and
sodium dodecyl sulfate (SDS) at 1 mM. The Km and Vmax values of the purified xylanase
were 9.67 mg/mL and 5.38 mmol/min/mg, respectively. The purified xylanase only showed
activity on xylan and hydrolyzed beechwood xylan to yield mainly xylotetraose and
xylobiose as end products which suggesting that it was an endo-xylanase.
