Insights into the mechanism for the high-alkaline activity of a novel GH43 8-xylosidase from Bacillus clausii with a promising application to produce xylose

Nowadays, alkali-tolerant 8-xylosidases and their molecular mechanism of pH adaptability have been poorly studied. Here, a novel GH43 8-xylosidase (XYLO) was isolated from Bacillus clausii TCCC 11004, and the recombinant 8-xylosidase (rXYLO) was most active at pH 8.0 and stable in a broad pH range (7.0-11.0), exhibiting superior alkali tolerance. Molecular dynamics simulation indicated that XYLO showed a notable overall structural stability and an enlargement of substrate binding pocket under alkaline condition, resulting in the formation of a new hydrogen bond between substrate and Arg286 of XYLO, and the tight binding played a key role in improving the XYLO activity with the increasing pH. Moreover, rXYLO with an endo-xylanase resulted in high xylose yields by hydrolyzing alkali-extracted xylan from agricultural wastes. This work would provide an alkali tolerant 8-xylosidase, enhance the understanding for the relationship of structure and activity adapted to the high-alkaline environment, and promote its application in xylose production.