Optically pure (R)-beta-butyrolactone as an important chiral building block in the syntheses of various biologically active compounds and biodegradable polymers was prepared from (R,S)-beta-butyrolactone through kinetic resolution. Candida antarctica lipase B (CALB) with a high enantiomeric ratio of 198 enantioselectively catalyzed the ring opening of the racemate with methanol in methyl tert-butyl ether at 45 A degrees C and yielded the remaining (R)-beta-butyrolactone. A detailed kinetic analysis indicated that methanol and (R)- and (S)-methyl ester all acted as competitive inhibitors for the enzyme. Comparisons of the theoretical and experimental conversions for both enantiomers were further made and elucidated. The thermodynamic analysis implied the enantiomer discrimination for the transition states of both enantiomers to be entropy-driven in the temperature range investigated. Moreover, preliminary results from the lipase reusability, feed-batch operation, and remaining substrate recovery were addressed.