Lipid extraction from microalgae by molten salt/ionic liquid mixtures

Most biodiesel produced in Korea is derived from imported vegetable oils (palm and soybean oils). Recently, a great deal of research effort has been devoted to biodiesel production that utilizes microalgae as a domestic oil source. Microalgae are photosynthetic microorganisms capable of converting carbon dioxide and water to macromolecules such as lipids, polysaccharides and proteins under light conditions. Some microalgae show high oil productivity relative to the capacities of plant oil, and offer the additional advantage of saving plants for food-crops purposes. Conversion of microalgae to biodiesel typically includes the following four steps: microalgae cultivation, cell harvesting, lipid extraction, and biodiesel conversion. In this study, lipid extraction from C. vulgaris was performed by using mixtures of molten salt and ionic liquid. The yield-enhancing effects of blending of molten salt with ionic liquid were investigated. Among the three molten salts (Zn(NO₃)₂∙6H₂O, Mg(ClO₄)₂∙6H₂O, and FeCl₃∙6H₂O), FeCl₃∙6H₂O showed a high lipid extraction yield (113.0 mg/g cell) and good reaction performance. When FeCl₃∙6H₂O was mixed with [Emim]OAc (5:1, w/w), the lipid extraction yield increased to 227.6 mg/g cell, a performance similar to that of single [Emim]OAc (218.7 mg/g cell). The lipid extraction from C. vulgaris was improved by the synergistic effects of molten salt and ionic liquid with different ions.