The esterification of palmitic acid with ethanol was investigated at various temperatures (35−70 °C) in the presence of three lipases (Novozym 435, Lipolase 100T, and hog pancreas lipase) in supercritical carbon dioxide (SCCO2) and under solvent-free conditions. All enzymes showed an optimum temperature of 55 °C under both conditions. The effect of water and ethanol addition on the esterification of acid was also investigated. The conversion obtained in SCCO2 and under solvent-free conditions with Novozym at optimal conditions was 74 and 97%, respectively. Although a higher apparent yield was obtained under the solvent-free conditions due to higher substrate and enzyme concentrations, the reaction in supercritical carbon dioxide is better because of lower enzyme loading, higher reaction rates and easier downstream processing.
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