Enzymatic methanolysis of castor oil for the synthesis of methyl ricinoleate in a solvent-free medium

Abstract

Several lipases of commercial grade were screened to catalyze the methanolysis of castor oil, and an immobilized Candida antarctica (Novozym 435) had the highest activity among the lipases tested. To enhance the yield of methyl ricinoleate, several reaction parameters were optimized. The optimum temperature was 50 degrees C, and the original water content of lipase was sufficient to maintain the activity of lipase and additional water Supplied inhibited the methanolysis of castor oil. Because the lipase was deactivated by methanol, the reaction was tested by three-step addition of 1 molar equivalent of methanol to the oil. However, the oil was not completely converted to its methyl esters. The final reaction mixture using, 3 molar equivalents of methanol to the oil consisted of 70% methyl ricinoleate, 18% monoricinoleate, 11% diricinoleate, and trace triricinoleate at the equilibrium state. The yield of methyl ricinoleate was 97% at 6 molar ratio of methanol to the oil with 300 g of castor oil and 6 g of immobilized Candida antarctica at 50 degrees C within 24 h.