Kinetics and specificity of Lipozyme-catalysed oil hydrolysis in supercritical CO(2)

Blackcurrant seed oil is rich in linoleic and linolenic acids. Selective enzyme-catalysed oil hydrolysis was studied with aim to obtain different levels of alpha- and/or gamma-linolenic acid in the mixture of liberated fatty acids and in the fraction of di- and monoacylglycerols, making them suitable for special dietary needs. The oil was dissolved in supercritical carbon dioxide flowing through a packed bed reactor (temperature 40 degrees C, pressure 15-28 MPa, and superficial velocity 0.1-0.7 mm s(-1)) with Lipozyme(R), a 1,3-specific lipase from Mucor miehei immobilised on a macroporous ion-exchange resin. The enzyme activity was stable as long as water precipitation in the reactor was prevented. The reaction was found to be controlled by both Michaelis-Menten kinetics and mass transfer. The maximum rate of fatty acids liberation per unit amount of enzyme, 2.6 x 10(-3) mol s(-1) kg(-1), was achieved at the maximum flow velocity and pressure. Compared to oil, the liberated fatty acids contained more alpha-linolenic, palmitic and stearic acids, while di- and monoacylglycerols contained increased levels of gamma-linolenic and stearidonic acids