PURIFICATION AND CHARACTERIZATION OF AN ENDOXYLANASE FROM THE CULTURE BROTH OF Bacillus cereus BSA1

摘要

An extracellular xylanase from the fermented broth of Bacillus cereus BSA1 was purified and characterized. The enzyme was purified to 3.43 fold through ammonium sulphate precipitation, DEAE-cellulose chromatography and followed by gel filtration through Sephadex G-100 column. The molecular mass of the purified xylanse was about 33 kDa. The enzyme was an endoxylanase as it initially degraded xylan to xylooligomers. The purified enzyme showed optimum activity at 55°C and at pH 7.0 and remained reasonably stable in a wide range of pH (5.0-8.0) and temperature (40-65°C). The K_m and revalues were found to be 8.2 mg/ml and 181.8 u.mol/(min mg), respectively. The enzyme had no apparent requirement of cofactors, and its activity was strongly inhibited byCu~(++), Hg~(++). It was also a salt tolerant enzyme and stable upto 2.5 M of NaCl and retained its 85% activity at 3.0 M. For stability and substrate binding, the enzyme needed hydrophobic interaction that revealed when most surfactants inhihited xylanase activity. Since the enzyme was active over wide range of pH, temperature and remained active in higher salt concentration, it could find potential uses in biobleaching process in paper industries.