Tuning Pseudomonas cepacea lipase (PCL) activity in supercritical fluids

Pseudonionas cepacea lipase (PCL) was used to catalyse the transesterification reaction between 1-phenylethanol and vinyl acetate in supercritical carbon dioxide (SCCO2). The enzyme, which is very selective towards one of the isomers of 1-phenylethanol, was very stable in the supercritical medium and showed higher reaction rates. The effect of SCCO2 pressure on the catalytic efficiency of PCL at a constant temperature was evaluated. With increasing pressure of the reaction medium the catalytic efficiency of the enzyme considered improved resulting in negative activation volume (-1340 cm(3)/mol) approaching critical values. A study of the kinetic mechanism in the SCCO2 reaction medium was also per-formed. Moreover supercritical sulphur hexafluoride (SCSF6) was used as reaction medium as a point of comparison with SCCO2. Preliminar data showed high stability of the enzyme in this supercritical medium and kinetic curve reported point out increased reaction rates in comparison to those achieved in SCCO2. (C) 2004 Elsevier B.V. All rights reserved.