Investigation of castor oil reactions with immobilized lipase enzyme

The use of enzymes as biocatalysts for organic hydrolysis and transformations provides many advantages, such as molecular recognition and selective catalysis. Lipase, triacylgliserol acylhydrolase, is one of the most used enzymes for hydrolysis and transformation reactions. In this study, lipase was immobilized on agarose beads via covalent bonding and used to catalyze the hydrolysis/transesterification of castor oil in ethanol medium. Castor oil is a triglyceride of fatty acids and lipases can be used for enzymatic hydrolysis /transesterification of castor oil to produce ricinoleic acid/ricinoleoic acid esters under mild conditions. In ethanol medium, both of the hydrolysis and transesterification reactions were occurred. The activity of immobilized lipase was assayed by measuring the release of nitrophenol at 346 nm fromp-nitrophenyl butyrate as substrate. The synthesized immobilized lipase was used for enzymecatalyzed hydrolysis/transesterifaciton of castor oilat room temperature without the use of any surfactants and salts. The main hydrolysis and transesterification products were ricinoleic acid and ricinoleic acid ethyl ester, respectively. The immobilization and hydrolysis/transesterification conditions were investigated to find maximum reaction yield. Better results were obtained when 90% ethanol was used as solvent than other buffer-ethanol mixture. 87% (40% ricinoleic acid and 47% ethyl ricinoleate) conversion was obtained with using 1.0 g of castor oil at 72 hours.