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Extracellular xylanases free of cellulase produced by the alkalophilic bacteria Bacillus pumilus was purified to homogeneity throughout the precipitation with (NH 4 ) 2 SO 4 , Q-Sepharose chromatography and characterized. The purified xylanases were proteins, with molecular mass ~14 kDa (Xyl 1), ~ 35 kDa (Xyl 2) and ~ 60 kDa (Xyl 3) as determined by SDS-PAGE. The optimal temperature and pH for the action of the enzyme were at 50 o C and 7 respectively. They exhibited thermal stability over a range of 20 to 40 o C at pH-7 and has retained 85 % at 60 o C. The activity strongly inhibited by 10 mm of Hg 2+ , SDS and Fe 2+ . The xylanase exhibited Km and Vmax values were 4.0 mg/ ml, 5000 µmol/ min/ mg protein (Xyl 1) as well as 3.5 mg /ml, 3448 µmol/ min/ mg of protein (Xyl 2) for oatspelt xylan.

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