Role of deep eutectic solvents for the extraction of polysaccharides from seaweed for food applications

The accelerating demand for green bioprocessing has positioned seaweed polysaccharides as expensive bioresources owing to their conformational diversity and varied bioactivities. Their relevance in functional foods and pharmaceuticals further emphasises the need for efficient and sustainable extraction strategies. The majority of existing extraction techniques frequently negotiate polysaccharide integrity, purity, and yield. In response, deep eutectic solvents (DES) have arisen as promising sustainable solvents, advancing tunable physicochemical characteristics and improved selectivity on polysaccharide functional groups. This review methodically assesses recent progress in the extraction of crucial seaweed polysaccharides, comprising alginate, fucoidan, laminarin, and carrageenan, employing DES/DES-assisted advanced technologies. The importance of Kamlet-Taft (KT) parameters is in-depth explored to understand DES-polysaccharide interactions and justify differences in solubilization and recovery proficiencies. Among the reviewed mixtures, choline chloride:glycerol and choline chloride:urea steadily displayed superior performance, with the former accomplishing advanced yields and the latter supporting careful solubilization. The relative insights presented emphasise that extraction results are affected by DES mixtures, seaweed species, and energy-assisted techniques such as microwave- and ultrasound-assisted extraction. Overall, this review highlights the possibility of DES-based green extraction approaches to attain competent and sustainable retrieval of seaweed polysaccharides, along with delivering a mechanistic knowledge for impending solvent design.