Improvement of the Thermostability of Xylanase from Thermobacillus composti through Site-Directed Mutagenesis

Thermostability is an important property of xylanase because high temperature is required for its applications, such as wood pulp bleaching, baking, and animal feedstuff processing. In this study, XynB from Thermobacillus composti, a moderately thermophilic gram-negative bacterium, was modified via site-directed mutagenesis (based on its 3D structure) to obtain thermostable xylanase, and the properties of this enzyme were analyzed. Results revealed that the half-life of xylanase at 65°C increased from 10 to 50 min after a disulfide bridge was introduced between the α-helix and its adjacent β-sheet at S98 and N145. Further mutation at the side of A153E named XynB-CE in the C-terminal of this α-helix enhanced the half-life of xylanase for 60 min at 65°C. Therefore, the mutant may be utilized for industrial applications.