An isolated xylosidase from Bacillus stearothermophilus NRRL B-18659, Bacillus stearothermophilus NRRL B-18660 and Bacillus stearothermophilus NRRL B-18661 is disclosed. The xylosidase has a maximum activity at about pH 6.0 and at about 75.degree. C., maintains at least about 60% of its maximum activity at about 65.degree. C. and pH 7 after 4 hours, is resistant to end-product inhibition maintaining over 75% of maximum activity in the presence of 1 molar xylose and has an isoelectric point of about 5.0. The xylosidase can be used in a method of hydrolyzing xylan present in wood pulp at temperatures of at least about 60.degree. C. and a pH of at least about 7.0. The xylosidase is used along with at least two xylanases and an arabinofuranosidase isolated from the above Bacillus stearothermophilus strains.