Rational stepwise screening of operational variables in deep eutectic solvent-mediated chitin extraction from spider crab shells

Chitin is one of the most abundant biopolymers and has attracted growing interest due to its biodegradability, renewability, and expanding applications. However, conventional chitin extraction methods rely heavily on harsh chemicals and energy-intensive processes. Herein, a protocol for isolating chitin from spider crab shells using a sequential Deep Eutectic Solvent optimization strategy is established. The experimental process systematically screened solvent parameters, first identifying systems outperformed with acidic, neutral and basic formulations. Among the acidic candidates, choline chloride:lactic acid (ChCl:LA) was selected for its superior efficiency and sustainability profile. Subsequent optimization of the solid-to-liquid ratio revealed that 1:15 is sufficient to maximize mass transfer, minimizing solvent usage. Then, temperature and time profiling defined two distinct operating windows that achieved comparable high removal efficiencies: a rapid higher-temperature and a lower-temperature route. Physicochemical characterization via ATR-FTIR, XRD, and solid-state 13 C CP/MAS NMR was employed to validate the identity of the isolated material. Notably, NMR analysis provided definitive evidence of the α-chitin polymorph and confirmed the preservation of a fully acetylated backbone without undesirable deacetylation, corroborating the native structure with high crystallinity. Specific energy monitoring revealed a trade-off: the 80 °C process is efficient when time saving is desired, whereas the 30 °C process is efficient when energy saving is prioritized, consuming 25% less energy, quantitatively challenging the assumption that faster processing yields the lowest energy footprint. These findings offer a scalable, low-carbon footprint solution that allows for strategic selection between maximum throughput and minimum energy consumption.