Enantioselective resolution of racemic ibuprofen esters using different lipases immobilized on octyl sepharose

Here we report the stereoselective hydrolysis of racemic esters catalyzed by Candida rugosa lipase (CRL) and Rhizopus oryzae lipase (ROL) immobilized on octyl-sepharose via physical adsorption. Hydrophobic immobilization caused to almost six fold hyperactivation with 229.2 and 81.3 U/mg enzyme for immobilized CRL and ROL, respectively (13.2 and 48.75 U/mg for corresponding free enzyme). Based on the preliminary results, CRL was chosen for further investigation. The performance and yield of the reaction were evaluated as a function of the critical reaction parameters such as temperature, enzyme to substrate ratio and organic co-solvent. An increase in the temperature resulted to decrease in enantioselectivity of hydrolysis reaction. The hydrolysis reactions were carried out in presence of two organic solvents; n-hexane and isooctane. Generally n-hexane was a better co-solvent compared to isooctane. High enantioselective hydrolysis of the racemic esters (yielding S(+) ibuprofen; ee ≥ 95%) can be achieved using the immobilized CRL. Among various esters the kinetic resolution of ibuprofen butyl ester yielded the best results (E value 70 and 74; conversion 14.6 and 8.9 in n-hexane and isooctane, respectively). The immobilized derivatives were re-used in four cycles and showed little decrease in enantiomeric excess of (S)-ibuprofen. 96.7 eep and conversion 14.6 in first cycle reached to 90.5 eep and conversion 11.3 in the forth cycle.