Green extraction of biomolecules from algae using subcritical and supercritical fluids

Biomolecules present in algae, such as carbohydrates, proteins, pigments, and lipids, have wide applications as ingredients in different cosmeceutical, pharmaceutical, and nutraceutical products. Research efforts have been made to establish efficient extraction processes of the high-value bioactive compounds from algae to overcome the limitations of traditional extraction processes. Supercritical fluid extraction (SFE) and subcritical water extraction (SWE) are identified as economically sustainable, promising green extraction technologies which have wide applicability in the extraction of valuable bioactive molecules from natural resources including micro- and macroalgae. This review presents a detailed discussion for the extraction of biomolecules from the algae using the SFE and SWE techniques. In addition, the improvement of these technologies has been discussed considering the extraction of different bioactive and valuable compounds from different algae strains. Optimized process conditions and choice of solvents in the SFE and SWE processes depend on the biomass composition. Research endeavors for the enhancement of extraction yield of the different biomolecules are addressed. The integrated extraction process by combining the SFE and SWE techniques appears to be an effective method for extracting different valuable bioactive molecules. This review also discussed the perspective and challenge for using SFE and SWE processes on algae.