Development of Microstructured Chitosan Nanocapsules with Immobilized Lipase

This study developed three microstructured chitosan nanocapsules with immobilized lipase to explore chitosan-lipase interactions at different pH levels. Chitosan undergoes complete protonation or deprotonation based on pH level. Three distinct pH levels were examined: 5.5, where chitosan is fully protonated; 6.5, where chitosan is partially protonated/deprotonated; and 7.5, where chitosan is fully deprotonated. The nanocapsules exhibited nanoscale dimensions and the microstructures showed porous morphology. Immobilized lipase showed improved temperature stability, compared to free enzyme, especially in lipase supports at pH 5.5 and 7.5 due to electrostatic and hydrophobic interactions. The interactions between chitosan and lipase influenced the microenvironment around the active site, resulting in an optimum pH of 8 for all supports. Immobilized lipase at pH 5.5 and 7.5 displayed the best reusability in the hydrolysis of p -nitrophenyl palmitate under reaction conditions of 37 °C and pH 8. During refrigeration storage, all immobilized lipases maintained total activity for 7 days, but lipase immobilized at pH 6.5 maintained more the activity after 28 days. Therefore, this study has developed promising immobilized lipase, standing out not only for industrial application concerning cost-effectiveness, but also for the innovation in investigating the influence of chitosan-lipase interactions during immobilization. Graphical Abstract