FISH OIL ETHANOLYSIS BY LIPOZYME RM IM IN SUPERCRITICAL CARBON DIOXIDE

RODRIGO MELGOSA , M. TERESA SANZ, ÁNGELA G. SOLAESA , ALMUDENA V. MERCHÁN , SAGRARIO BELTRÀN; DANIELA LAMAS

Niza

Congreso; ECCE10+ECAB3+EPIC5; 2015

European Federation of Chemical Engineering

Fish oil is a natural source of omega-3 polyunsatturated fatty acids (n-3 PUFAs). The implications of n-3 PUFAs in human health have been the subject of an enormous number of epidemiological and clinical studies, scientific articles and reviews in the last years. A brief summary can be found in the work by Rubio-Rodríguez et al. (2010). The beneficial effects of n-3 PUFAs have drawn the attention of the pharmaceutical and food industry in the last years. However, the use of n-3 PUFAs as active compounds in pharmacology or functional ingredients in food products demands previous modification and concentration steps into a chemical form easily metabolised by human organism and with a good stability against oxidation (e.g. monoacylglyderide, MAG). Traditional and novel methods to obtain these fish oil derivatives have been reviewed by Rubio-Rodríguez et al. (2010), including enzymatic methods using supercritical fluids as reaction media. In this work, ethanolysis of a mixture of tuna and sardine oil by commercial immobilized lipase Lipozyme RM IM from Rhizomucor miehei (Novozymes) has been carried on in supercritical carbon dioxide (SC-CO2 )as reaction medium. The reaction has been performed in a batch stirred tank reactor with an internal volume of 100 mL. Samples were taken periodically during 24 h from the bottom of the reactor through a siphoned capillary. Temperatures and pressures investigated ranged between 50-80ºC and 7.5-20 MPa. Initial substrate molar ratio has been varied from 2:1 to 38:1 (ethanol:fish oil). Enzyme loading was fixed at 5% wt. of substrates. Neutral lipid profile of the reaction samples was determined by High Performance Liquid Chromatography (HPLC). Ethanol and glycerol were analysed by High Temperature Gas Chromatography (HT-GC), using triethylenglycol as internal standard. Results obtained showed a positive effect of the initial substrate molar ratio on the total conversion and the initial reaction rate from 2:1 to 6:1. Above this point, higher amounts of ethanol possibly caused enzyme inhibition. Different temperature and pressure combinations were also assayed at a fixed initial substrate molar ratio of 6:1. In the range investigated, a maximum in total conversion, initial reaction rate and MAG production was found at 65ºC and 10 MPa, possibly because of the physical properties of the solvent, which may be favourable due to lower mass transfer limitations (Knez 2009). Above this optimal temperature, lower conversion due to thermal deactivation of the catalyst was observed. Increasing pressure from 7.5 to 10 MPa at 50ºC led to a sharp increase in total conversion and initial reaction rate, possibly due to the solvation of SC-CO2 in the liquid phase, which significantly increases the diffusivity and reduces the viscosity and the surface tension. Further pressure increments showed a gradual decay. Dilution effects due to SCCO2 solvation have been proposed as the main reason of this behaviour (Laudani et al. 2007).