Improved enantioselectivity of Candida rugosa lipase towards ketoprofen ethyl ester by a simple two-step treatment

A novel two-step acetone treatment method was developed to improve the enan tioselectivity of Candida rugosa lipase (CRL) towards the hydrolysis of (R, S)-ketoprofen ethyl ester. After two-step acetone treatment of crude CRL, t he CRL was harvested as precipitates and used for the production of optical ly pure (S)-ketoprofen. The specific activity of two-step acetone-treated C RL was 2.05 kU/mg protein, which corresponds to a 2-fold increase over that of crude CRL. The two-step acetone-treated CRL was considerably more enant ioselective than the crude CRL towards (R,S)-ketoprofen ethyl ester, yieldi ng an enantiomeric excess (% ee(p)) of about 100% and an enantiomeric ratio (E) of > 100. The hydrolysis activity of acetone-treated CRL increased wit h an increase in reaction temperature but the enantiomeric excess was > 99% regardless of reaction temperature. The production of optically pure (S)-k etoprofen was performed for 108 h in a scaled-up batch reactor containing 2 00 g of (R,S)-ketoprofen ethyl ester. Consequently, about 90 g of (S)-ketop rofen with an optical purity of 98% was recovered from the reaction mixture . (C) 2000 Elsevier Science Ltd. All rights reserved.