Recombinant expression and characterization of a neutral xyloglucanase MtXG from Mycothermus thermophilus

Xyloglucanase cleaves the β-1,4-glycosidic bond in xyloglucan and has been used in the food, feed, and paper industries. This study presents the cloning, heterologous expression, and characterization of a neutral xyloglucanase, designated as MtXG, derived from the thermophilic fungus Mycothermus thermophilus. The recombinant MtXG enzyme expressed in Pichia pastoris exhibited optimal activity at pH 7.0 and 75 ℃, demonstrating remarkable stability over a broad range of pH (4.0 to 7.5) and temperature (up to 60 ℃ for 2 h). Furthermore, MtXG demonstrated high specificity towards xyloglucan and showed varying degrees of tolerance to various metal ions, with notable resistance to Zn²⁺, NH₄⁺, K⁺, Mn²⁺, and Na⁺. The removal of the linker and carbohydrate-binding module from MtXG significantly affected its enzymatic properties, including a reduction in optimal pH and temperature but improved pH and temperature stabilities. Notably, the addition of MtXG to a commercial cellulase preparation resulted in a significant enhancement of reducing sugar yield from tobacco leaves, indicating its potential to facilitate the enzymatic degradation of lignocellulosic biomass for industrial applications. This study highlights the unique properties of MtXG and its potential as a valuable tool for lignocellulose bioconversion processes.