A tunable deep eutectic solvent platform for efficient and sustainable agarose extraction

Abstract

Here, a rationally designed deep eutectic solvent (DES) composed of benzyltriethylammonium chloride and N-methylurea is introduced as a tunable and mild platform for agarose extraction from Gelidium amansii. The DES features a markedly depressed melting point, moderate viscosity, and a dense hydrogen-bonding network, enabling efficient biomass penetration and selective polysaccharide solubilization. Relative to multi-step conventional alkali–EDTA processing, the single-step DES approach operates under milder conditions, reduces energy consumption and chemical waste, avoids strong alkalis and excessive water consumption, and provides higher agarose recovery. Molecular simulations further reveal that hydrogen bonding between N-methylurea and agarose drives dissolution, whereas electrostatic interactions between quaternary ammonium cations and sulfated galactans enable selective impurity precipitation.