Abstract
Microalgae contain valuable biologically active lipophilic substances such as omega-3 fatty acids and carotenoids. In contrast to the recovery of vegetable oils from seeds, where the extraction with supercritical CO2 is used as a mild and selective method, economically viable application of this method on similarly soluble oils from microalgae requires, in most cases, much higher pressure. This paper presents and verifies hypothesis that this difference is caused by high adsorption capacity of microalgae. Under the pressures usually applied in supercritical fluid extraction from plants, microalgae bind a large fraction of the extracted oil, while under extremely high CO2 pressures their adsorption capacity diminishes and the extraction rate depends on oil solubility in supercritical CO2. A mathematical model for the extraction from microalgae was derived and applied to literature data on the extraction kinetics in order to determine model parameters.
Highlights
IntroductionMore than 50,000 species are supposed to exist, but only about 30,000 have been studied [1]
Microalgae are photosynthetic unicellular microorganisms presenting a great genetic variety.More than 50,000 species are supposed to exist, but only about 30,000 have been studied [1]
The model derived in this study is able to simulate the effects of particle size, flow rate, pressure, and temperature on the mass transfer resistance and the effects of pressure and temperature on the equilibrium parameters solubility, adsorption capacity, and partition coefficient
Summary
More than 50,000 species are supposed to exist, but only about 30,000 have been studied [1]. These microorganisms have not been much used for the production of chemicals, though for some of these, such as some polyunsaturated fatty acids, they are the greatest reserve of the biosphere [2]. The lipid content of microalgae can go up to 85% dry weight, though values between 20% and 40%. The production yield of these compounds relies on the conditions of culture, one of the main factors being the amount of nitrogen to control the lipid content [4]
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