CONTINUOUS ENANTIOSELECTIVE TRANSESTERIFICATION IN ORGANIC-SOLVENTS -USE OF SUSPENDED LIPASE PREPARATIONS IN A MICROFILTRATION MEMBRANE REACTOR

A continuously stirred tank reactor equipped with a microfiltration me mbrane unit for effective retention of solid enzyme particles in organ ic solvent systems was constructed. A microfiltration membrane with po re size 0.1 mu m based on a polypropylene matrice was used for enzyme retention and showed no loss of performance or denaturation by the org anic solvent. The stereoselective transesterification reaction of (+/- )-trans-sobrerol with vinyl acetate as both acyl donor and solvent was chosen as a model system. Lipase PS from Pseudomonas sp. was used in its native form without further modification steps and remained active and highly stereoselective at 50 degrees C when applied to the reacti on system for about 600 h of continuous operation. (1S,5R)-sobrerolace tate and (+)-(1R,5S)-sobrerol could be obtained in the reactor outlet stream at approximately 48% conversion with enantiomeric excesses ee(P ) approximate to 92% and ee(S) approximate to 80%, respectively. Furth ermore, theoretical kinetic studies showed that Limitations in enantio meric purity due to the characteristics of an ideal mixed tank may be sufficiently overcome by designing a simple two-stage process.