Extraction of Polysaccharide by Ultrasound-Assisted Deep Eutectic Solvent-Based Three-Phase Partitioning System: Process Optimization, Partial Structure Characterization, and Antioxidant Properties.

An innovative ultrasound-assisted deep eutectic solvent-based three-phase partitioning (UA-DES-TPP) system was developed for the sustainable extraction of polysaccharide (FCP). Using a hydrophobic DES composed of dodecanoic acid and octanoic acid (1:1 molar ratio), a phase behavior-driven separation mechanism was established. The system was systematically optimized through single-factor experiments and response surface methodology (RSM), achieving a maximum FCP yield of 9.22 ± 0.20% under optimal conditions (liquid-solid ratio 1:24.2 g/mL, top/bottom phase volume ratio 1:1.05 /, ammonium sulfate concentration 25.8%). Structural characterization revealed that FCP was a heteropolysaccharide primarily composed of glucose and mannose with α/β-glycosidic linkages and a loose fibrous network. Remarkably, the DESs demonstrated excellent recyclability over five cycles. Furthermore, FCP exhibited significant concentration-dependent antioxidant activities: 82.3 ± 3.8% DPPH radical scavenging at 8 mg/mL, 76.8 ± 0.8% ABTS scavenging, and ferric ion reducing power of 45.53 ± 1.07 μmol TE/g. This study provides a new path for the efficient and sustainable extraction of bioactive macromolecules.