Thermo- and pH-tolerance xylanase immobilized magnetic responsive Zr-MOFs composites as recyclable biocatalyst for the degradation of corn straw

Xylanase is a natural and high-efficiency catalyst for the degradation of xylan to reducing sugar. However, the catalytic performance of xylanase is greatly limited by its poor activity and stability at the harsh condition. To overcome this issue, covalent immobilization of xylanase on a magnetic porous MOFs material with core-shell structure, UIO-66-NH2 carrier was applied to improve the catalytic activity and stability of xylanase. Several tools were employed to monitor the preparation and immobilization processes, magnetic properties, and the structural/chemical characteristics of the biocatalyst. 77.9% of the activity for xylanase was retained after immobilization. Moreover, the thermal stability in terms of half-life of the immobilized enzyme was three times higher than that in free form, and which had higher catalytic efficiency for hydrolysis of xylan. Furthermore, the greater temperature and wider pH ranges of the activity stability were achieved for the immobilized xylanase in compared with free one. Notably, the biocatalyst exhibits both excellent storage stability and could be easily separated using a magnet, which is conducive for its reusability. And nearly 70% of its initial activity was retained after seven recycles during the hydrolysis of corn straw. These features indicate that the present immobilization method is promising prospect for the industrial application of enzyme.