NaDES-based biorefinery of Spirulina (Arthrospira platensis): A new path for sustainable high value-added metabolites

To meet the criteria of modern extraction, it is essential to use solvents that simultaneously reach the standards of green chemistry and allow the extraction of a wide spectrum of bio-compounds. Natural Deep Eutectic Solvents (NaDES), as a green solution, meet this difficult task and represent a satisfactory alternative to organic solvents. Microalgae are recognized as a sustainable resource to produce polar and non-polar metabolites, such as carotenoids, free fatty acids (FFA) and phycobiliproteins. Among them, Spirulina (Arthrospira platensis) is one of the most studied, due to its strong potential for food, health and cosmetic. In this work, two biorefinery scenarios were investigated using polar and non-polar NaDES. The first one is a combination of a polar/non-polar sequential solid/liquid extraction together with a liquid–liquid extraction of the polar extract. The second scenario implements an innovative triphasic solid/liquid/liquid approach, based on the simultaneous use of polar and non-polar NaDES in the solid/liquid extraction step. Several NaDES were screened in this study to identify the best polar/non-polar NaDES pair. According to the results, the use of the triphasic approach allowed an increase of the productivity by a factor 4 for chlorophylls and FFA, and by a factor 2 for carotenoids. It was also interesting to note that the phycocyanin-enriched polar fraction achieves much higher levels of purity than the corresponding single-phase extraction for both applied biorefinery scenarios. These results pave the way for the first time for a microalgae biorefinery entirely based on the use of NaDES and industrially credible.