Abstract
To develop greener extraction alternatives for microalgae biomass, ultrasound assisted extraction (UAE) and pressurized liquid extraction (PLE) with different biobased solvents were investigated, demonstrating that both techniques are useful alternatives for algal lipid extraction. Specifically, Nannochloropsis gaditana lipids were extracted by UAE and PLE at different temperatures and extraction times with sustainable solvents like 2-Methyltetrahydrofuran (2-MeTHF) and its mixtures with ethanol and other alcohols. The best oil yields for both PLE and UAE of N. gaditana were achieved with the mixture of 2-MeTHF:ethanol (1:3), reaching yields of up to 16.3%, for UAE at 50 °C and up to 46.1% for PLE at 120 °C. Lipid composition of the extracts was analyzed by HPLC-ELSD and by GC-MS to determine lipid species and fatty acid profile, respectively. Different fractionation of lipid species was achieved with PLE and solvent mixtures of different polarity. Thus, for the extraction of glycolipids, ethanolic extracts contained higher amounts of glycolipids and EPA, probably due to the higher polarity of the solvent. The optimized method was applied to microalgae Isochrysis galbana and Tetraselmis chuii showing the potential of mixtures of biobased solvents like 2-methyl-THF and ethanol in different proportions to efficiently extract and fractionate lipids from microalgal biomass.
Highlights
Microalgae have recently attracted considerable interest as raw materials and have been described as great sources of bioactive lipids as polyunsaturated fatty acids (PUFAs).Microalgae contain polar lipids like glycolipids that include eicosapentaenoic acid (EPA; 20:5 n-3) and docosahexaenoic acid (DHA; 22:6 n-3), and have been widely recognized as bioactive compounds for human health
In order to compare both pressurized liquid extraction (PLE) and ultrasound assisted extraction (UAE) techniques, solvents selected for UAE and the mixture of 2-MeTHF:ethanol (1:3) were employed with PLE in the first place
The results prove that the use of 2-methyl-THF could be a promising hexane substitute in solvent mixtures with alcohols when extracting by PLE more polar compounds from microalgae, promoting the principles of green chemistry through the use of alternative solvents of biological origin instead of hexane mixtures
Summary
Microalgae have recently attracted considerable interest as raw materials and have been described as great sources of bioactive lipids as polyunsaturated fatty acids (PUFAs).Microalgae contain polar lipids like glycolipids that include eicosapentaenoic acid (EPA; 20:5 n-3) and docosahexaenoic acid (DHA; 22:6 n-3), and have been widely recognized as bioactive compounds for human health. Microalgae have recently attracted considerable interest as raw materials and have been described as great sources of bioactive lipids as polyunsaturated fatty acids (PUFAs). N-3 LC-PUFA dietary supplements are widely available, usually in triacylglycerol (TAG), non-esterified free fatty acid (FFA), and ethyl ester (EE) forms from fish oil, algae, and other sources [4]. It has been shown that EPA and DHA in the form of polar lipids (phospholipids and glycolipids) exhibit better bioactivity and bioavailability than in the TAG or EE forms. DHA polar lipids showed more efficient bioactivity than the TAG, EE, and FFA forms in decreasing hepatic and serum total cholesterol and TAG levels and increasing n-3 concentration in the brain during a short period
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