title: [Identification and mode of action of a xylanase A purified from the culture filtrate of Bacillus pumilus WL-11].
abstract: Microbial xylanases have received a great deal of attention in the last two decades for their potential applications in food, paper making and animal feed industries. Bacillus pumilus WL-11 was identified as a producer of alkane xylanase free of cellulase after screening soil samples of paper-making factories. The xylanase A (XylA) was purified to homogeneity from the culture filtrate of Bacillus pumilus WL-11 by (NH4) 2SO4 precipitation, CM-Sephadex and Sephadex G-75 chromatographies. The molecular mass of XylA is estimated to be 26.0 kD by SDS-PAGE and its isoelectric point is 9.5. The apparent Km is 16.6 mg/mL and V(max) is 1263 micromol/(min x mg) towards oat spelt xylan. XylA is optimally active between pH 7.2 and 8.0, and stable at pH 6.0 to 10.4. The enzyme is optimally active at 45 degrees C - 55 degrees C and stable at temperature below 45 degrees C, with its half time of activity of 35 min and 15 min at 55 degrees C and 60 degrees C respectively. HPLC analysis revealed that hydrolysis patterns of xylans from oat spelt, birch wood and beech wood by purified XylA were different. The XylA is determined to be an endo-beta-1,4-xylanase, as it generated mainly xylotriose and no xylose was detected among the three hydrolysates. XylA has strong hydrolytic activity towards the pentose in the hydrolysates of beech wood and birch wood xylans, but was not active to the pentose in the hydrolysate of oat spelt xylan. The crude WL-11 enzyme can efficiently hydrolyze oat spelt xylan to a series of xylo-oligosaccharides, suggesting its potential application in nutraceutical industry.
authors.affiliation: School of Biotechnology, Southern Yangtze University, Wuxi 214036, China.
authors.forename: Zheng-Hong
authors.initials: ZH
authors.lastname: Xu
authors.forename: Wen-Yi
authors.initials: WY
authors.lastname: Tao
mesh_terms: D001407:Bacillus / Q000145:classification / Q000201:enzymology*; D001426:Bacterial Proteins / Q000378:metabolism*; D003470:Culture Media; D043364:Endo-1,4-beta Xylanases / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D043364:Endo-1,4-beta Xylanases