Optimization of Microbial Rennet Encapsulation in Alginate – Chitosan Nanoparticles

•Rennet was encapsulated in alginate-chitosan nanoparticles prepared by ionotropic gelation and polyelectrolyte complexation.•Encapsulated enzyme had higher activity at various pH and temperature values in comparison to the free enzyme.•No statistical differences were found between the kinetic parameters (Km and Vmax) of encapsulated and free enzymes.•Enzyme release mechanism from nanoparticles in all pH values followed the Fickian diffusion. The milk-coagulating enzyme, rennet, is widely used in cheese making. Recently stabilization of rennet, especially in accelerated cheese ripening, has received considerable interest. As we know encapsulation is one of the enzyme immobilization methods, which could increase enzyme stability. In this study, the effects of alginate, chitosan and, CaCl2 on rennet encapsulation were evaluated and optimized using RSM. Under the optimal conditions alginate, chitosan, and CaCl2 were 0.04%, 0.1%, and 0.1% respectively. At the optimum point, encapsulation efficiency, particle size, and zeta potential were evaluated to be 61.8%, 323 nm, and 25 mV, respectively. The effect of temperature and pH on the enzyme activity was evaluated, and the results showed that encapsulated enzyme had higher activity at various pH and temperature in comparison with the free enzyme. Also, the enzyme release data in all pH values were fitted to Korsmeyer-Peppas model and the n exponent indicated that the release mechanism was Fickian. The electrostatic interactions between enzyme, alginate, and chitosan were confirmed by infrared spectroscopy. No statistical difference was found between the Km and Vmax of encapsulated and free enzymes.