No abstract

With the hydrolytic resolution of (R,S)-naproxen 2,2,2-trifluoroethyl thioesters in water-saturated isooctane as a model system, improvements of the specific lipase activity and thermal stability were found when a crude Carica papaya lipase (CPL) was partially purified and employed as the biocatalyst. The partially purified Carica papaya lipase (PCPL) was furthermore explored as an effective enantioselective biocatalyst for the hydrolytic resolution of (R,S)-profen thioesters in water-saturated organic solvents. The kinetic analysis in water-saturated isooctane indicated that both acyl donor and acyl acceptor have profound influences on the lipase activity, E-value, and enantioselectivity. Inversion of the enantioselectivity from (S)- to (R)-thioester was found for (R,S)-fenoprofen and (R,S)-ketoprofen thioesters that contained a bulky substituent at the meta-position of 2-phenyl moiety of the acyl part. Kinetic constants for the acylation step were furthermore estimated for elucidating the kinetic data and postulating an active site model. The thermodynamic analysis indicated that the enantiomer discrimination was driven by the difference of activation enthalpy (DeltaDeltaH) and that of activation entropy (DeltaDeltaS), yet the latter was dominated for most of the reacting systems. The postulated active site model was supported from the variation of DeltaDeltaH and DeltaDeltaS with the acyl moiety, in which a good linear enthalpy-entropy compensation relationship was also illustrated. A comparison of the performances between Candida rugosa lipase (CRL) and PCPL indicated that PCPL was superior to CRL in terms of the better thermal stability, similar or better lipase activity for the fast-reacting substrate, time-course-stability, and lower enzyme cost.

Installation of an impermeable barrier between the plates substantially increases the separation efficiency by reducing the remixing effect. Theoretical considerations show that when the barrier is installed at the best position, maximum separation, maximum concentration of top product, or minimum concentration of bottom product may be obtained. Considerable improvement is obtained when the column is operated at the conditions leading to the best performance.

: A recycle dialysis stirred cell has been successfully used for integrating the reaction and product recovery of the lipase-catalyzed hydrolysis of olive oil in bis(2-ethylhexyl) sodium sulfosuccinate (A0T)-iso-octane reversed micelles. The resistance of membrane to reversed micelles was monitored by the water content and found to be 95.9 ' YO rejection after 24 h and 93.4 YO rejection after 48 h. The resistance of the membrane to free surfactants, by monitoring the UV absorption, was found to be 98.5 % rejection after 10 h and 97.3 % rejection after 24 h. Mathematical formulations involving the enzymatic reaction coupled with mass transfer were developed for predicting the performance of a membrane reactor. Theoretical predictions in terms of time course of oleic acid concentrations were found to be in agreement with the experimental results.Key words : reversed micelles, lipase, dialysis, permeability coefficient. Receiver phase