Enhanced catalytic performance of lipase covalently bonded on ionic liquids modified magnetic alginate composites

We prepared ionic liquids (ILs) modified magnetic alginate nanoparticles and used these as supports for lipase immobilization. The novel supports were characterized using Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (¹HNMR), vibrating sample magnetometry (VSM), thermogravimetry (TG), transmission electron microscopy (TEM) and water contact angle (WCA) measurements. The immobilized lipase (PPL-IL-MSA) exhibited high activity, 2.1-fold higher than that compared to free lipase and 1.59-fold higher compared to immobilized lipase without IL (PPL-MSA). In addition, the pH and temperature application range of PPL-IL-MSA were both found to be broader than that of free lipase and PPL-MSA. The thermal stability, denaturation stability, and reusing stability of PPL-IL-MSA were also higher than those of other samples. After 10 times of reuse, the residual activity of PPL-IL-MSA was 89.7% higher than that of PPL-MSA (84.4%). Furthermore, the kinetic constant K_m of PPL-IL-MSA was 13.7 mg/mL lower than that of free lipase (21.2 mg/mL) and PPL-MSA (18.4 mg/mL). Circular dichroism (CD) was used to study the secondary structure of enzymes in order to explain the mechanism of the performance improvement of PPL-IL-MSA. This work involving the development of a new supports for enzyme immobilization may serve as a reference for further studies in this field.