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Enzyme efficiency was investigated in the lipase-catalyzed hydrolysis ofcanola oil in supercritical carbon dioxide (SCCO). Immobilized lipase from Mucor miehie (Lipozyme 1M) was used as the catalyst and the results showed that enzyme efficiency dropped at high pressures indicating a possible change in enzyme microstructure. Therefore, scanning electron microscopy (SEM) was used as a supplementary tool to investigate microstructural stability ofthe enzyme under supercritical conditions. SEM images of the treated enzymes did not demonstrate any apparent structural changes with a change in pressure (24.0 and 38.0 MPa), enzyme load ofthe reactor (1.0 and 5.0 g), C02flow rate (0.5 and 3.9 L/min) and the oil content (extractedfrom 3.0 and 15.0 g canola flakes) ofSCC02. However, a change at the molecular level is a possibility, which requires further investigation

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