Unveiling the potential of betaine/polyol-based deep eutectic systems for the recovery of bioactive protein derivative-rich extracts from sardine processing residues

Abstract

• Betaine/polyol-based deep eutectic systems (DES) were used as extraction solvents. • Protein derivative-rich extracts were obtained from sardine waste biomass. • Betaine:Propylene glycol (1:3) has led to the highest protein yields. • DES with lower polarity and water content have led to extracts with higher bioactivity. In addition to nutritional and functional properties, fish proteins have been consistently associated to different biological activities. In the work reported herein, the application of betaine/polyol-based deep eutectic systems (DES) was explored for the recovery of bioactive protein derivative-rich extracts contained in sardine processing waste streams. Aiming at maximizing the extraction of target compounds, the impact of operating temperature, extraction time, and solid/liquid ratio on the extraction performance was evaluated. Extractions using DES as alternative solvents were compared to a conventional solid/liquid extraction with water. The antioxidant activity of sardine extracts was assessed using the Oxygen Radical Absorbance Capacity assay, while their antimicrobial potential, as well as DES’, was evaluated towards Staphylococcus aureus and Escherichia coli . Results have shown that the protein maximum extraction yields obtained with DES were similar to those achieved with water (162.2 ± 20.4 compared to 145.7 ± 2.9 mg protein /g dry residue ). Nevertheless, most DES extracts obtained at 80 °C were able to surpass the antioxidant and antimicrobial potential of water extracts, with an increase in activity of up to 3-fold and more than 250-fold, respectively, for the most promising extracts. Furthermore, results have also shown that the DES tested present antimicrobial potential, which might have enhanced the bioactivity of the extracts. Therefore, the study reported herein reinforces that DES represent not only a possible alternative extraction media for the recovery of protein derivatives from fish biomass, but also a promising vehicle for the obtained extracts, with potential to be used in industrial applications.