Selective enrichment of polyunsaturated fatty acids by hydrolysis of fish oil using immobilized and stabilized Rhizomucor miehei lipase preparations

Abstract

Immobilization of Rhizomucor miehei lipase (RML) by two different methods is reported. In the first approach RML was directly immobilized on epoxy functionalized silica particles in a mild condition. In the other approach and to perform oriented immobilization, the epoxy functionalized support was partially modified by introducing iminodiacetic acid groups fallowed by addition of Cu2+. In this type of immobilization the covalent linkage takes place after initial adsorption of the enzyme on the support via metal chelate affinity interaction. The results showed higher thermal stability for the derivative obtained by this method. Co-solvent stability of the derivatives and free RML was also studied in presence of 10 and 20% of six polar organic solvents (DMSO, THF, acetonitrile, 1-propanol, 2-propanol and dioxane). The results showed improved stabilities for both derivatives, silica-epoxy-IDA-RML in particular. The ability of the immobilized preparations and the free enzyme to catalyze hydrolysis of fish oil was determined at different conditions. The results revealed that all the derivatives discriminate between cis-5,8,11,14,17-eicosapentaenoic acid (EPA) and cis-4,7,10,13,16,19-docosahexaenoic acid (DHA) in favor of EPA. The content of EPA and DHA increased with time and the amount of biocatalyst during the hydrolysis process. Reusability of the enzyme greatly improved after immobilization.