Preparation and modification of chitosan particles for Rhizomucor miehei lipase immobilization

Abstract

Chitosan particles, suitable as immobilization support, were prepared by precipitation and modified by reductive amination in order to graft linear aliphatic chains of 12 carbon atoms to their native amine groups. Their physical characterization was performed by different techniques: differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), air-water contact angle analysis, among others. Lipases from Rhizomucor miehei (RM) were immobilized by adsorption at low ionic strength onto different modified chitosan microspheres. Their ability to catalyze the acidolysis reaction between sunflower oil and palmitic and stearic free fatty acids was evaluated in a solvent medium. Effects of modification conditions on the particles hydrophobic character, lipase adsorption and acidolysis activity were investigated. Modified particles were bigger and more hydrophobic than unmodified ones. The most active biocatalyst achieved a change in the composition of palmitic and stearic acid from a value of 9.6% in the original oil to 49.1% in the final structured lipids, representing an almost 3-fold enzyme hyperactivation. This high conversion was maintained during 7 reuse cycles (168 total hours). The results demonstrated that the chitosan modification was effective in order to adsorb and hyperactivate RM lipases.