Kinetic and thermodynamic studies of eicosapentaenoic acid extraction from Nannochloropsis oceanica using tetramethyl ammonium chloride and microwave irradiation

Abstract

Microalgae have garnered widespread attention as a sustainable source of pharmaceuticals and nutraceuticals. As for extracting lipids from microalgae, the combination of microwave-assisted extraction (MAE) and ionic liquids (IL) is shown to be promising. However, such an undertaking usually requires a large consumption of expensive ILs. This study innovatively employs tetramethyl ammonium chloride ([TMAm][Cl]) as an additive in water medium to associate with microwave-assisted ionic liquid extraction (MAILE) in extracting lipids from Nannochloropsis oceanica (N. oceanica) microalgae. In extraction, knowledge of reaction kinetics is crucial since it provides the foundation for developing, controlling, and improving the processes of extraction. Herein, using MAILE, lipids are extracted from N. oceanica microalgae and transesterified to eicosapentaenoic acid (EPA). Mass transfer kinetics are, therefore, investigated using the first and second-order rate law and Patricelli’s model. In the development of models, the influence of temperature (60–90°C) and reaction time (1–25 min) on EPA extraction is empirically evaluated. From the thermodynamic study, the positive values of ΔS (+0.10 kJ mol-1K-1) and ΔH (+32.50 kJ mol-1) and the negative value of ΔG (-1.68 to -4.75 kJ mol-1) confirm that this process is endothermic in nature, irreversible and spontaneous. MAILE proves to be a promising approach for the extraction of high-quality EPAs. Due to its low cost, rapid operation, and environmental friendliness, it is seen to be suitable for both pharmaceutical and nutraceutical applications.