Ángela García Solaesa

Kinetic study and kinetic parameters of lipase-catalyzed glycerolysis of sardine oil in a homogeneous medium

The production of polyunsaturated fatty acids (PUFAs) concentrates by enzymatic catalysis has gained interest due to their stereospecificity and the milder conditions employed compared to the use of inorganic catalysts. The enzymatic glycerolysis of sardine oil by Lipozyme® 435 to get PUFA concentrates in the forms of di- and monoacylglycerols (DAGs, MAGs) in an optimized amount of tert-butanol as the organic solvent was studied. First, mass transfer limitation of the reaction system was analyzed. The effects of different operating variables such as lipase loading, temperature and feed composition were investigated. A semi-empirical kinetic model based on the reversible elementary reactions of glycerolysis and hydrolysis of the glycerides was employed to correlate the experimental kinetic data. A molar ratio glycerol:oil of 3:1 was the optimum, which produced more than 84 wt% of MAG at 323 K. A comparison with other glycerolysis systems was performed using MAG yield, reaction rate and significance of kinetic parameters.

Kinetic Study for the Ethanolysis of Fish Oil Catalyzed by Lipozyme® 435 in Different Reaction Media

The ethanolysis of fish oil in various reaction medium (tert-pentanol, n-hexane and solvent free system) catalyzed by the immobilized commercial lipase Lipozyme(®) 435 (Candida Antarctica) at atmospheric pressure has been studied in this work. The effect of some kinetic parameters, such as the amount of lipase, temperature and the initial reactant molar ratio ethanol:oil on monoacyglyceride and ethyl ester yield has been analyzed. Experimental data were successfully correlated by a simple kinetic model based on the elementary reactions proposed in this work. At high initial reactant molar ratio the three elementary steps can be considered as irreversible. However the reaction rate constants ratio for the deacylation of monoglyceride to glycerol decreased by decreasing the molar ratio ethanol:oil. The reaction rates are slower in n-hexane as reaction medium compared to tert-pentanol and a solvent-free system, at the experimental conditions essayed in this work. In this last case, ethanol acts as solvent for reaction and as reactant.

Substrates emulsification process to improve lipase-catalyzed sardine oil glycerolysis in different systems. Evaluation of lipid oxidation of the reaction products

Mono- and diacylglycerols rich in omega-3 have a great interest due to their good bioavailability and oxidation stability compared with other kind of omega-3 concentrates. The main drawback in mono- and diacylglycerols production by glycerolysis is the immiscibility of the substrates, oil and glycerol. To improve mass transfer rates, avoiding the use of organic solvents, emulsification of both reactants as reverse micelles (glycerol-in-oil) was carried out previous to lipase-catalyzed sardine oil glycerolysis. Substrate emulsification yielded higher reaction rates compared to kinetics with no previous emulsification, but still lower than in organic solvents. To avoid the use of organic solvent, SC-CO2 was used as reaction medium but no kinetic advantages were demonstrated in the pressure range from 15 to 25 MPa. By increasing temperature, from 40 to 90°C, reaction rates increased both in a solvent-free system and in SC-CO2 medium. It was also found that an increase in temperature does not lead to an increase in the final oxidation status of the reaction products. This behavior was due to the adsorption capacity of the Lipozyme 435 support, giving lower oxidation status at the highest temperature, 80-90°C.