Characterization of a novel xylanase from Aspergillus flavus with the unique properties in production of xylooligosaccharides

A novel xylanase from the filamentous fungus Aspergillus flavus was purified and characterized as the beta-1, 4-endoxylanase (designed as AfXynB) with a molecular mass (32.2 kDa), which is different from all of the previously reported xylanases from the same strain. AfXynB was optimally active at pH 7.5 and 55 degrees C, respectively. It was stable up to 50 degrees C within range of pH 4.0-9.5, and displayed an excellent tolerance to various cations, reagents, and proteases. AfXynB showed specific activity toward beechwood xylan but no detected activity toward CMC and pNP-beta-D-xylopyranoside. The xylanase is a typical endo-xylanase; it could hydrolyze beechwood xylan to only yield xylobiose (X2) and xylopentaose (X5). Actually, this may be the first report for the endo-xylanases that displayed such a unique hydrolytic property. These findings in the present study have great implications for its future applications of the novel xylanase.