Structure-function relationships and industrial integration of extremophilic xylanases for sustainable...

The instability of traditional glycoside hydrolases in the harsh conditions of pretreatment hinders the industrial scale enzymatic synthesis of the xylo-oligosaccharides using lignocellulosic biomass from agricultural wastes. However, extremophilic xylanases found in thermophiles, halophiles, and acidophiles/alkaliphiles, are intrinsically stable at high temperatures, extreme pH, and high salinity. Their resilience is based on discrete molecular adaptation such as ion-pair networks, hydrophobic cores, and surface electrostatics. In this review, extremophilic xylanase engineering using protein engineering and synthetic biology strategies for xylo-oligosaccharide production is systematically summarized. Meanwhile, techno-economic and life cycle assessments confirm improved sustainability and economic efficiency of XOS production in the context of a biorefinery. In the future, further effort will still be required for extremophilic xylanases to enhance the commercial implementation of the process towards sustainable bioprocessing.