Recent progress in the microbial production of Xylanase

Endo-1,4-β-D-xylanase (EC 3.2.1.8, abbreviated as xylanase) is widely distributed in various plant-associated mollusks, insects, and microorganisms, catalyzing the degradation of xylan-a major component of plant cell walls. Based on their diverse catalytic mechanisms toward xylan chains, major xylanases from microbial species are summarized and categorized into various glycoside hydrolase (GH) families through phylogenetic analysis in this review. Xylanases, particularly GH10 and GH11 families, play versatile and critical roles in many plant-based industries, including food and feed, biofuels, pulp and paper, and pharmaceuticals. Nevertheless, persistent challenges of xylanases during practical applications are pointed out as their properties and microbial production occurs because native xylanases show weak operational stability under extreme conditions (high temperature, pH extremes, high salinity). To improve the performance of xylanases, protein engineering technique for xylanase structure optimization, and amino acid modification is analyzed as a powerful approach in many cases. In parallel, famous industrial microbial chassis, such as Escherichia coli, Komagataella phaffii systems for recombinant xylanase production are proved as a solution of growing industrial demand of xylanases recently. The strategy of combining emerging technologies with "design-production-immobilization-application" technological cycle is proposed as the key development direction of xylanase based on the systematic evaluation of the status, challenges, and development prospects of microbial xylanases production, encompassing xylanase characteristics, structure modification and production, applications and future directions.