Activity and stability of lipases from different sources in supercritical carbon dioxide and near-critical propane

The stability and activity of lipases from Pseudomonas fluorescens, Rhizopus javanicus, Rhizopus niveus, porcine pancreas and Candida rugosa in a non-solvent system at atmospheric pressure, in supercritical carbon dioxide (SC CO(2)), and near-critical propane at 100 bar and 40 degreesC were studied. Esterification of n-butyric acid with ethanol and isoamyl alcohol was used as a model system. In supercritical carbon dioxide there was a great loss in activity of the examined lipases. Decreased relative activity of lipases in SC CO(2) was attributed to the interactions between CO(2) and the enzyme. The second reason for this effect was the differences in water partitioning between the enzyme and its surroundings. In contrast, the use of near-critical propane improved the activity of lipases in the comparison to the non-solvent system by four- (porcine pancreas lipase) to nine-times (Rhizopus javanicus lipase). The use of near-critical propane also improved the thermal stability of porcine pancreas lipase compared with the non-solvent system. The calculated deactivation constant for esterification between butyric acid and isoamyl alcohol, catalyzed by porcine pancreas lipase, showed that there was more than twice as much inactive as active enzyme in the non-solvent system studied whereas the ratio in propane was 1. (C) 2001 Society of Chemical Industry.