Covalent immobilization of lipase on aldehyde-functionalized gum arabic/magnetic chitosan nanoparticles for soybean oil hydrolysis

Efficient recovery and reuse of lipase remain major challenges in lipid biocatalysis. In this study, aldehyde-functionalized gum arabic-modified magnetic chitosan nanoparticles (GA-CHO/MCNPs) were developed as a biopolymer-based magnetic carrier for lipase immobilization. The carrier was prepared by in situ coprecipitation followed by surface modification with periodate-oxidized gum arabic. Under optimized conditions, the protein loading and protein-based immobilization yield reached 112.5 ± 4.8 mg g −1 and 84.6 ± 2.9%, respectively, while the recovered activity was 62.7 ± 3.1%. Compared with free lipase, Lipase@GA-CHO/MCNPs showed a higher optimum temperature (45 versus 35 °C), improved tolerance to pH and thermal treatment, and convenient magnetic recovery. Immobilization increased the apparent K m from 2.12 to 3.85 mM and decreased V max and k cat , indicating diffusional and steric limitations associated with the carrier. Nevertheless, the immobilized lipase achieved a soybean oil hydrolysis yield of 91.2%, retained 82.3% of its initial activity after 10 reuse cycles, and retained 84.8% activity after 30 d of storage at 4 °C. The results support successful lipase immobilization through an aldehyde-amine-mediated coupling strategy and demonstrate the potential of GA-CHO/MCNPs as a recoverable biopolymer-based carrier for soybean oil hydrolysis.