Thermo- and pH-tolerant xylanase-immobilized magnetic Zr-MOF composites as recyclable biocatalysts for the degradation of corn straw

Abstract

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 under harsh conditions. To overcome this issue, covalent immobilization of xylanase on a magnetic porous MOF material with a core–shell structure, UIO-66-NH₂ carrier, was conducted to improve the catalytic activity and stability of xylanase. Several tools were employed to monitor the preparation and immobilization processes, magnetic properties, and structural/chemical characteristics of the biocatalyst. It was found that 77.9% of the activity of xylanase was retained after immobilization. Moreover, the thermal stability in terms of half-life of the immobilized enzyme was three times higher than that of the free form; the immobilized enzyme also showed higher catalytic efficiency for hydrolysis of xylan. Furthermore, stable activity at higher temperatures and a wider pH range was achieved for the immobilized xylanase compared with the free catalyst. Notably, the biocatalyst exhibited both excellent storage stability and could be easily separated using a magnet, which is conducive to its reusability. Moreover, nearly 70% of its initial activity was retained after seven recycles for the hydrolysis of corn straw. These features indicate that the present immobilization method is promising for the industrial application of enzymes.