Continuous enantioselective esterification of trans-2-phenyl-1-cyclohexanol using a new Candida rugosa lipase in a packed bed bioreactor

Enantioselective resolution of trans-2-phenyl-1-cyclohexanol (TPCH) by a Ca ndida rugosa lipase, obtained by fermentation in the laboratory, and immobi lised on EP100 polypropylene powder has been carried out using isooctane as solvent and propionic acid as esterifying agent. The study have included t he utilisation of this biocatalyst in a batch process and the optimisation of the esterification conditions by means of a Box-Hunter-based experimenta l design. The main variables controlling the process, concentration of acid and alcohol, have been numerically optimised using initial esterification rate as objective function. The optimal concentrations for the batch proces s were 50 mM for the alcohol and 71 mM for the acid. This esterification re action kinetics corresponded to a reversible Michaelis-Menten kinetic law f or the optimal conditions, which has permitted to select a plug-flow packed bed bioreactor as the most appropriate configuration to minimise the resid ence time and to avoid shear stress effect on the biocatalyst. The behaviou r of the continuous packed bed bioreactor at two different residence times (302 and 582 min) was in accordance with predictions from batch experiments , with slightly deviations (less than 10%). Continuous experiments maintain ed high values of enantioselectivity (enantiomeric factor was practically 1 ) and conversion near equilibrium value (35%) when long-time operation was carried out. Besides, long-time stability of biocatalyst has permitted to s cale-up the production of enantioenriched (1R,2S)-TPCH propionate to yield gram quantities. (C) 2000 Elsevier Science B.V. All rights reserved.