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Abstract: Lipases from Candida rugosa (CRL) and Pseudomonas cepacia (PCL) were co-lyophilized with cyclic oligoethers including four crown ethers and nine cyclodextrins (CyDs), and their transesterification activity and enantioselectivity in organic solvents were evaluated. The PCL co-lyophilized with each additive showed simultaneously enhanced enzyme activity and enantioselectivity when compared to the native lipase lyophilized from buffer alone; in contrast, such enhancement was not observed for the co-lyophilized CRL. Among the cyclic oligoethers examined, permethylated betaCyD (Me(1.78)betaCyD), as the most suitable additive, was used for the optimization of both the co-lyophilized PCL preparation and reaction conditions by determining the effects of varying the additive/lipase ratio, aqueous pH, the nature of organic solvents, and temperature. The initial rate determined for the transesterification between racemic 2,2-dimethyl-1,3-dioxolane- 4-methanol and vinyl butyrate in diisopropyl ether at 30degreesC increased by up to 17-fold and the enantioselectivity represented by E could be doubled. While there was an inverse correlation between temperature and enantioselectivity, with the Me(1.78)betaCyD-PCL co- lyophilizate, the reaction rate even at 0degreesC was much higher than that at higher temperatures in the native PCL- catalyzed reaction. Hence, this method seems to be of practical use for the large-scale production of optically active compounds