Immobilization of lipase on carboxylic acid-modified silica nanoparticles for olive oil glycerolysis.

In this study, the silica nanoparticles surface was modified by carboxylic acid with different number of alkyl chain and two different lipases were immobilized on it to increase the glycerolysis activity of the immobilized lipases in organic solvent system. Silica nanoparticles of about 15 nm diameter were grafted with various carboxylic acid modifiers from valeric, caprylic, capric, lauric, stearic and oleic acids. Lipases from Candida antarctica and Candida rugosa were immobilized onto the carboxylic acid, modified silica nanoparticles and used in the mono and diglycerides production through glycerolysis with or without organic solvents. When lipases immobilized on stearic acid-modified silica nanoparticles, both lipases gave higher activity compared to their corresponding free lipases. Immobilized C. rugosa were stable and reused for 11 cycles without loss in activity. The kinetic parameters, K m and V max of free and immobilized lipases were found using Lineweaver-Burk model. Results indicated that the immobilized lipase had a lower K m and V max when compared with the free lipase.