Purification and characterization of xylanase from alkali-tolerant Aspergillus fischeri Fxn1

Alkali-tolerant Aspergillus fischeri Fxn1 produced two extracellular xylanases. The major xylanase (M(r) 31,000) was purified to electrophoretic homogeneity by ammonium sulfate precipitation, anion exchange chromatography and preparatory PAGE. Xylose was the major hydrolysis product from oat spelt and birch wood xylans. It was completely free of cellulolytic activities. The optimum pH and temperature were 6.0 and 60 degrees C, respectively. pH stability ranged from 5 to 9.5 and the t1/2 at 50 degrees C was 490 min. It had a Km of 4.88 mg ml-1 and a Vmax of 588 mumol min-1 mg-1. The activity was inhibited (95%) by AlCl3 (10 mM). This enzyme appears to be novel and will be useful for studies on the mechanism of hydrolysis of xylan by xylanolytic enzymes.