Esterification of phenolic acids catalyzed by lipases immobilized in organogels.

Lipases from Rhizomucor miehei and Candida antarctica B were immobilized in hydroxypropylmethyl cellulose organogels based on surfactant-free microemulsions consisting of n-hexane, 1-propanol and water. Both lipases kept their catalytic activity, catalyzing the esterification reactions of various phenolic acids including cinnamic acid derivatives. High reaction rates and yields (up to 94%) were obtained when lipase from C. antarctica was used. Kinetic studies have been performed and apparent kinetic constants were determined showing that ester synthesis catalyzed by immobilized lipases occurs via the Michaelis-Menten mechanism.

Esterification reactions catalyzed by lipases immobilized in organogels: effect of temperature and substrate diffusion.

Rhizomucor miehei lipase was immobilized in hydroxy(propylmethyl) cellulose or agar gels containing lecithin or AOT microemulsions. The effect of the diffusion of substrates and products to this catalyst was studied, as well as the effect of temperature on the initial rate of ester synthesis. The composition of the gel affects the reaction rate due to mass transport phenomena. The apparent activation energies were higher for the systems based on agar, independently of the microemulsion used, and lower for the systems based on AOT microemulsions, independently of the polymer used.