Xylanase immobilization onto trichlorotriazine-functionalized polyethylene glycol grafted magnetic nanoparticles: A thermostable and robust nanobiocatalyst for fruit juice clarification

The covalent immobilization of xylanase onto the trichlorotriazine-functionalized polyethylene glycol grafted magnetic nanoparticles was exploited to generate a stabilized xylanase with improved catalytic activity and stability. Several tools were deployed to monitor the synthesis and immobilization processes, the loading capacity of nanocarrier, and the structural/chemical characteristics of the nanobiocatalyst. The optimum immobilization yield of xylanase was 260 mg xylanase/g nanocarrier in 20 mM phosphate buffer, pH 6.5 at 25 °C. A forward shift in optimum pH (6.5 to 7.5) and temperature (60 to 70 °C) of xylanase was observed after immobilization and the performance of immobilized enzyme was improved at high temperatures and pHs as affirmed by enhancement of vmax (2.69 to 6.01 U/mL) and decreases of Ea (14.61 to 13.41 kJ/mol). An increase in Km from 25.51 to 40.42 mg/mL was recorded after immobilization. The obtained results indicated augmented thermal stability of the immobilized xylanase. Notably, it showed good reusability as validated by retention of 50% of its initial activity after nine recycles in enrichment of the pineapple juice clarification after 120 min incubation at 50 °C, pH 4.5. The structural analysis revealed some partial changes in the α-helix and β-sheet content of the enzyme after several recycles.