Unveiling the Use of Hydrophobic Eutectic Solutions as Task-Specific Solvents To Recover Bacterioruberin from Haloferax mediterranei

Abstract

Haloarchaea make up a class of untapped marine microbial resources that constitute a promising source of valuable compounds with unique characteristics. Bacterioruberin is a C50 carotenoid produced by haloarchaea that possesses interesting antioxidant properties and bioactivities relevant to the food and cosmetic industries. As a substitute for the conventional organic solvents used in the extraction of nonpolar pigments, natural and biocompatible hydrophobic eutectic solvents (HES) based on the mixture of menthol with carboxylic acids were investigated for the extraction of bacterioruberin. Seven HES systems were screened both as neat solvents and in the presence of water. The menthol and levulinic acid mixture displayed a 4-fold improvement over both the ethanol control and the other HES, due to the dual action of its components. Additionally, the recovery of proteins could be achieved by the addition of water to the extract, resulting in a three-phase partition system and the formation of a protein-rich interfacial precipitate. The process intensification was assessed through the reuse of the eutectic phase over five successive extraction cycles, achieving a bacterioruberin-rich extract of 2.13 mgbacterioruberin mLHES-1. Finally, the carbon footprint of the process was determined. The results highlight the potential of HES as biocompatible solvents for the recovery of value-added compounds from marine biomass, while the use of three-phase partition allows the recovery of proteins producing a second product stream.