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

This work investigates the effect of supercritical carbon dioxide (SC-CO2) treatment on four commercial lipases. The influence of experimental conditions: temperature (35-70 degrees C), pressure (10-25 MPa), exposure time (1-3 h) and depressurization steps (1-3) on the residual activity was studied. Activity enhancement was verified for free enzymes (Palatase 20000 L and Lipozyme CALB L) treated at mild conditions; while the highest temperature and pressure and the longest exposure time assayed led to activity losses. On the other hand, activity losses or no significative effect of the treatment in the enzyme activity were observed on immobilized enzymes (Lipozyme RM IM and Lipozyme 435). Qualitative studies were also performed: Fluorescence emission spectra showed changes in the conformational structure of both two free enzymes after SC-CO2 treatment. Scanning electron micrographs showed morphological alterations in the immobilization supports of the treated enzymes; while infrared spectra did not show chemical modifications. (C) 2014 Elsevier B.V. All rights reserved.