Characterization of cellulase-free xylanases from the newly isolated Bacillus sp. strain BP-23

Abstract

A Bacillus strain with xylanase activity has been isolated. Maximum xylanase production was obtained when the strain was cultured in media supplemented with birchwood xylan or rice straw; production was repressed by glucose and xylose. The optimal temperature and pH for xylanase activity were 45–50 °C and 5.5–7.5, respectively. Crude xylanase was highly stable at a wide range of pH values, retaining 100% of the activity after 24 h of incubation at 37 °C in buffer at pH 10.0. Analysis by polyacrylamide gel electrophoresis and zymogram techniques showed four xylanase activity bands with apparent molecular masses of 32, 48, 61, and 66 kDa. The most active of them (molecular mass 32 kDa) apparently corresponded to a xylanase with an isoelectric point (pI) of 9.3 in isoelectrofocusing gels developed as zymograms. Four other 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 hydrolytic activity against the cellulosic substrate.Key words: Bacillus sp., xylanase, isolation.