Supercritical-fluid extraction of fungal lipids: Effect of cosolvent on mass-transfer rates and process design and economics

Abstract

The extraction of fungal lipids by supercritical CO 2 and CO 2 with 10 wt % ethanol was studied. The lipid solubility was measured from 40–60 °C and 200–700 bar, and was found to increase with increasing solvent pressure and temperature, although the crossover effect was observed. Mass transfer coefficients were fitted to experimental data and were found to increase with increasing solvent Reynolds number. No difference in mass-transfer coefficients was observed with the addition of the cosolvent. Using the experimental data, a mathematical model for a commercial extraction process was developed, and optimal values of the extractor pressure, solvent flow rate, and extraction time were computed. Since the lipid is more soluble in the CO 2 mixture, the optimal extractor pressure and extraction time were lower than those computed for a process with a pure CO 2 solvent. Capital and operating costs for the process were estimated and the addition of the cosolvent was found to lower the costs by over 40%. A comparison of the costs for the SFE process and the costs for a liquid-extraction process show that the SFE process is not competitive for this application, although the economics would be improved if wet fungal mycelia were contacted continuously with the supercritical solvent.