The potential of natural deep eutectic systems (NADESs) to efficiently extract astaxanthin (AXT) contained in crab shell wastes was evaluated. Different terpene-based mixtures were prepared and characterized. Aiming at maximizing the AXT recovery, we evaluated the effect of operating temperature and time on the extraction performance. As a proof of concept, this paper also highlights the potential of NADESs for AXT extraction from shrimp shells, mussels, and Haematococcus pluvialis. The biological potential of AXT-rich extracts; the AXT standard; and NADESs, their individual components, and equivalent physical mixtures was evaluated, including cytotoxicity, antiproliferative effects on human colorectal cancer cells, and antimicrobial potential against Staphylococcus aureus and Escherichia coli. Results showed that extractions with menthol:myristic acid (8:1) were able to match the AXT yield obtained by a Soxhlet extraction with acetone. Additionally, when using the same NADESs to recover AXT from the other biomasses under study, there was a 3-to 657-fold increase in yields when compared with the Soxhlet extraction. AXT-rich extracts obtained with NADESs showed antiproliferative and antimicrobial potential. This study suggests that NADESs can truly be used as alternative extraction media for the recovery of AXT from waste biomass and that these systems and respective extracts have the potential to be used as ingredients in industrial applications.

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This work tackles the quest for temperature-responsive greener solvents by synthesizing a hydrophobic deep eutectic solvent (DES) comprising menthol and decanoic acid. The low solubility of hydrophobic solvents in polar media was addressed by dispersing DES as oil-in-water nanoemulsions allowing their use in biomedical applications. DES-in-water nanoemulsions produced by ultrasound and membrane emulsification techniques were systematically compared. Microengineered isoporous membranes having 9 μm pore size were fabricated by laser machining. A membrane pitch of 100 μm was optimized to produce nanoemulsions 58.7 ± 0.4 nm in size at a dispersed phase flow rate of 0.02 mL min −1 leading to a new approach termed as membrane-assisted nanoemulsification. Subsequently, the optimized DES-based nanoemulsions subjected to antimicrobial susceptibility testing assays were 32 times more active against the Gram-positive bacteria, S. aureus ATCC 6538, than against the Gram-negative bacteria, E. coli ATCC 8739. In contrast to the nonemulsified DES or its individual components, 16 times less chemicals were required to inhibit bacterial activity when tested as nanoemulsions, suggesting increased bioavailability and a synergistic effect of all components in nanoemulsions potentiating their antibacterial activity. Lastly, membrane-assisted nanoemulsification offers sustainable production of nanoemulsions with a better control over size and dispersity along with lowered energy consumption when compared to ultrasound emulsification.

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