Selective resolution of racemic menthol by lipases in the aqueous/organic solvent system

Abstract

This project involved the resolution of menthol by lipase in an aqueous/organic system. The study was divided into two main experimental parts. First, experiments concerning selection of suitable system components for this specific reaction. It was found that Candida cylindracea lipase, hexyl acetate, and iso-octane were the suitable types of enzyme, acyl donor, and solvent for the reaction. Moreover, an organic system was discovered to be more suitable than an aqueous/organic system due to the more complex downstream separation process the latter system required owing to its stable emulsions formed. Second, experiments regarding the determination of optimum conditions and kinetics of the transesterification of racemic menthol and hexyl acetate by Candida cylindracea lipase in iso-octane using experimental designs. The optimum conditions found were racemic menthol concentration 73 mM, hexyl acetate concentration 360 mM, temperature 66 ํC, and stirring speed 110 rpm. The final conversion were 27.12% calculated base on recemic menthol. The reaction was found to follow random bi bi mechanism which kinetic parameters were determined as Vmax = 100.28 mu mol/hr-g.enz, alphaKA = 33.92 mM, alphaKB = 8.42 mM, KA = 248.22 mM, KB = 60.92 mM, K11 = 51.19 mM, and K12 = 481.98 mM and the rate equation can be expressed as V = 100.28[A][B]/2066.4+8.42[A](1+[A]/481.98) + 33.92[B](1+[B]/51.19) + [A][B] mu mol/hr-g.enz