Enzymatic activity and conformational and morphological studies of four commercial lipases treated with supercritical carbon dioxide

Abstract

This work investigates the effect of supercritical carbon dioxide (SC-CO2) treatment on four commer-cial lipases. The influence of experimental conditions: temperature (35–70◦C), pressure (10–25 MPa),exposure time (1–3 h) and depressurization steps (1–3) on the residual activity was studied. Activityenhancement was verified for free enzymes (Palatase 20000 L and Lipozyme CALB L) treated at mildconditions; while the highest temperature and pressure and the longest exposure time assayed led toactivity losses. On the other hand, activity losses or no significative effect of the treatment in the enzymeactivity were observed on immobilized enzymes (Lipozyme RM IM and Lipozyme 435). Qualitative stud-ies were also performed: Fluorescence emission spectra showed changes in the conformational structureof both two free enzymes after SC-CO2treatment. Scanning electron micrographs showed morphologicalalterations in the immobilization supports of the treated enzymes; while infrared spectra did not showchemical modifications.