First Assessment of Feasibility of Liquid-Liquid Extraction of Xantophylls from Bittern

Abstract

Carotenoids are valuable compounds that can be naturally produced by microorganisms. Some of these grow and proliferate in hypersaline environments, such as saltworks, where essential nutrients and key stress conditions (e.g., high temperature, salinity, and solar irradiation) are naturally present. For this reason, their concentration can be significant in bittern, the waste solution generated by saltworks at the end of the salt production process. In the present work, to the best of the authors’ knowledge, the direct extraction of pigments from real natural bittern is reported for the first time, to demonstrate the technical feasibility of recovering pigments from a waste solution, avoiding upstream costs and limiting the costs for cells harvesting and lysis. Following a bittern concentration step, achieved via UltraFiltration, liquid-liquid extraction was performed by adding an extracting solvent to the concentrated bittern, briefly shaking and subsequently centrifuging it. The light phase obtained after centrifugation was analysed by UV-VIS spectrophotometry and HPLC analysis. The efficacy of different solvents was assessed, namely methanol, ethyl acetate, hexane, and acetone. Acetone was identified as the most effective solvent and the extraction process was further optimized by testing different volume ratios and centrifugation settings, resulting in a xanthophyll concentration of 3.08 ± 0.03 mg/L in the acetone phase, starting from 0.41 ± 0.05 mg/L in the concentrated bittern. Based on these results liquid-liquid extraction appears to be a feasible approach, although further optimization is still required.