Inulinase immobilized gold-magnetic nanoparticles as a magnetically recyclable biocatalyst for facial and efficient inulin biotransformation to high fructose syrup.

To date, the high cost of enzyme production, lack of enzyme reusability and operational stability are the main limitations of the enzyme's application in industry. In this work, inulinase was covalently immobilized on the surface of glutathione-coated gold magnetic nanoparticles (GSH-AuMNPs). The synthesized NPs were fully characterized. The effects of different restriction factors such as substrate concentration, temperature, and pH on the performance and stability of the enzyme were examined. The maximum activity and immobilization yield were estimated 83% and 93%, respectively. The immobilized inulinase showed maximum activity at pH 4.5 and 60 °C. The kinetic parameters of the immobilized enzyme were not changed significantly after the immobilization process. The reusability assessment indicated that approximately 78% of the initial activity of immobilized inulinase remained after ten times recycling. The storage stability of inulinase was improved by the immobilization process. The inulin hydrolysates were checked by HPLC and the end products only contained two components, 98% of fructose and up to 2% of glucose in both free enzyme and immobilized enzyme systems. This study introduced a simple, effective and inexpensive immobilization process, which is applicable in different biomedical, biotechnological and food industries.