Optimization of the immobilization of xylanase from Thermomyces lanuginosus to produce xylooligosaccharides in a batch type reactor

• The xylanase was immobilized on MWCNTs following different strategies. • Xyl/CNT-Glu showed 24.0-fold higher thermal stability than free xylanase at 70 °C. • The immobilization can tune the enzyme specificity and selectivity of xylanase. • Xylose was not formed in all the immobilized xylanase catalyzed reactions. The xylanase from Thermomyces lanuginosus was immobilized following very different protocols, using 3-aminopropyl (Xyl/CNT-NH 2 ) and carboxylic acid (Xyl/CNT-C) functionalized multi-walled carbon nanotubes or after glutaraldehyde activation of CNT-NH 2 (Xyl/CNT-Glu). It was also immobilized on carboxylic acid functionalized multi-walled carbon nanotubes via carbodiimide chemistry (Xyl/CNT-COOH). The free and all the immobilized xylanase derivatives showed maximal catalytic activity at pH 7.5 and at 65 °C. Xyl/CNT-Glu showed 24.0-fold higher thermal stability than the free xylanase at 70 °C. The immobilized xylanase derivatives were used for the production of xylooligosaccarides, the reaction courses and the yields showing a dependence on the immobilization protocol. The highest XOS yield (22.1%) was obtained using Xyl/CNT-Glu after 8 h of reaction at pH 75 and 65 °C.