The versatility of chitin and its derivatives has allowed their utilization in a wide range of applications, from wastewater treatment to pharmaceutical or biomedical industries. However, even though the extraction method used industrially is extremely efficient, it involves the use of strong acids and bases and results in the disposal of large quantities of toxic effluents. Deep eutectic systems (DESs) have emerged as a promising new class of alternative solvents, including for chitin recovery. Yet, the assessment of their toxicity has often been neglected. Therefore, in this work, the phytotoxicity of choline chloride (ChCl)/organic acid-based DESs toward wheat seeds was evaluated by measuring different growth parameters and stress biomarkers. DESs were then explored for the efficient recovery of chitin contained in brown crab shell residues at varying conditions of temperature and processing time as well as with and without water addition. The obtained chitin was then characterized through different analytical techniques and compared to a standard as well as to chitin obtained by a conventional acid/alkaline hydrolysis. Results have shown that by applying a ChCl/lactic acid-based DES (which was the system that showed the least phytotoxic effects on wheat; EC50 ≥ 1.6 mg/mL) at 130 °C, it was possible to obtain pure chitin (up to 98%) with characteristics similar to those presented by commercial chitin or chitin recovered by conventional hydrolysis in a shorter time (more than 8-fold faster), thus suggesting that ChCl/organic acid-based DESs can truly represent a low-phytotoxic alternative extraction media for the recovery of chitin from the crab shell biomass.

Green and sustainable chemistry principles have been employed in different industries to create greener and safer chemicals and processes, by replacing hazardous solvents with safer and more efficient ones. A state-of-the-art analysis on deep eutectic systems (DES) shows their consistent growth in the fields of chemistry, particularly as extraction solvents, mainly of bioactive compounds from natural sources. In this sense, a patent review was carried out, to highlight the relevance of DES, formed by natural compounds, in the cosmetic industry and the commercial added value of this technology at the industrial scale. Despite their good extraction efficiency, DES physicochemical properties need to be considered, as they may present some limitations in the process scale-up. This implies the study of several parameters, such as the cost of raw materials, the investment necessary to adapt or implement new equipment, energy consumption (for instance for pumping, heating, and stirring), and treatment of any by-products and wastes, in both the upstream and the downstream operations. Due to their inherent properties, DES can also be used as stabilizing agents of the bioactive compounds extracted, allowing their direct use in final products, namely in cosmetics, which is translated into a reduction of the downstream costs. This work further reports a case study of the extraction of grape anthocyanins with DES, and the necessary steps required to take this process from a laboratory scale to an industrial scale, targeting the cosmetic industry.