Purification and characterization of a thermophilic alkaline xylanase from thermoalkaliphilic Bacillus sp. strain TAR-1 |
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Authors: | Satoshi Nakamura Yutaka Ishiguro Ryuichiro Nakai Kenji Wakabayashi Rikizo Aono Koki Horikoshi |
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Abstract: | Thermoalkaliphilic Bacillus sp. strain TAR-1 isolated from soil produced an extracellular xylanase. The enzyme (xylanase R) was purified to homogeneity by ammonium sulfate fractionation and anion-exchange chromatography. The molecular mass of xylanase R was 40 kDa and the isoelectric point was 4.1. The enzyme was most active over the range of pH 5.0 to 10.0 at 50°C. The optimum temperatures for activity were 75°C at pH 7.0 and 70°C at pH 9.0. Xylanase R was stable up to 65°C at pH 9.0 for 30 min in the presence of xylan. Mercury(ll) ion at 1 mM concentration abolished all the xylanase activity. The predominant products of xylan-hydrolysate were xylobiose, xylotriose, and higher oligosaccharides, indicating that xylanase R was an endo-acting enzyme. Xylanase R had a Km of 0.82 mg/ml and a Vmax of 280 μmol min−1 mg−1 for xylan at 50°C and pH 9.0. |
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Keywords: | Xylanase Bacillus sp. Alkaliphiles Thermophiles Xylan Biobleaching |
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