Green extraction and purification of astaxanthin and lipids from the oleaginous microalgae Chromochloris zofingiensis

Sustainable extraction and purification of high-value compounds from microalgae require processes that minimize environmental impact while maintaining efficiency. This study presents a systematic approach for a more sustainable extraction of cellular lipids and astaxanthin from the oleaginous green microalgae Chromochloris zofingiensis , utilizing green and bio-based solvents, combined with liquid-liquid chromatography (LLC) for purification. Ten potential green and bio-based solvents were initially screened based on their physical properties, CHEM21 solvent guide ranking, and predicted ability to dissolve astaxanthin esters. Subsequently, biphasic ternary solvent systems containing water were identified for the extraction, and thermodynamic models were used to predict liquid-liquid equilibrium (LLE) when experimental data were unavailable. Systems were evaluated considering the biphasic region size, thermal energy demand for solvent evaporation, and the respective pressure of the evaporator. Four promising systems, 2-methyltetrahydrofuran and cyclopentyl methyl ether, with ethanol or 1-butanol, and water, were experimentally assessed for total extraction and astaxanthin yield, solvent consumption, and thermal energy required for solvent removal. These systems achieved comparable extraction performance to conventional solvents while offering superior health, safety, and environmental profiles. For selective purification with LLC, a thermodynamic model was applied to predict the LLE and partition coefficients of quaternary solvent systems. A greener solvent system, comprising hexamethyldisilazane, dimethyl carbonate, ethanol, and water, was identified, which facilitated the successful separation of astaxanthin and cellular lipids using LLC.