CHARACTERIZATION OF CELLULASE-FREE XYLANASES FROM THE NEWLY ISOLATED BACILLUS SP STRAIN BP-23

A Bacillus strain with xylanase activity has been isolated. Maximum xy lanase production was obtained when the strain was cultured in media s upplemented with birchwood xylan or rice straw; production was repress ed by glucose and xylose. The optimal temperature and pH for xylanase activity were 45-50 degrees C and 5.5-7.5, respectively. Crude xylanas e was highly stable at a wide range of pH values, retaining 100% of th e activity after 24 h of incubation at 37 degrees C in buffer at pH 10 .0. Analysis by polyacrylamide gel electrophoresis and zymogram techni ques showed four xylanase activity bands with apparent molecular masse s of 32, 48, 61, and 66 kDa. The most active of them (molecular mass 3 2 kDa) apparently corresponded to a xylanase with an isoelectric point (pI) of 9.3 in isoelectrofocusing gels developed as zymograms. Four o ther bands with xylanase activity were detected at pIs of 7.7, 5.6, 5. 0, and 4.5. Analysis for carboxymethylcellulase activity revealed that only the band of 48 kDa and the band with a pi of 7.7 showed hydrolyt ic activity against the cellulosic substrate.