A simple process for increasing the specific activity of porcine pancreatic lipase by supercritical carbon dioxide treatment

Treatment of crude porcine pancreatic lipase preparations (powders) with supercritical carbon dioxide (SC-CO2) at 75 degrees C and 150 bar leads to a time-dependent increase of enzyme activity (activities were measured prior and after SC-CO, treatment). After 24 h of incubation in SC-CO2, a maximum activity of 860% was measured compared to the untreated enzyme (using 1,2-O-dilauryl-rac-glycero-3-glutaric acid resorufin ester as substrate). SC-CO2 treatment caused a weight loss of about 4%. 0.47% of the weight loss (mean of three independent experiments) were separated as an oily extract in a tube that was connected with the extractor and through which depressurization was performed. In the extract, free fatty acids were found (mainly palmitic acid, stearic acid and oleic acid). No chemical modification on the protein reactive groups were found as studied by determination of reactive free amino groups, determination of free -SH groups and by determination of the carbonyl content (as an oxidation marker). No significant difference in the protein content between the untreated and SC-CO2 processed lipase powders were found. Tryptophan fluorescence emission spectra showed no change of the emission maximum indicating no larger protein conformational change. SC-CO2-treated lipase showed no loss of its increased activity after storage in a freezer for 6 months. (C) 2000 Elsevier Science B.V. All rights reserved.