Integrated pH-responsive three-phase system: Time- and solvent-efficient biorefining of Camellia oleifera waste into...

Camellia oleifera seed cake (COSC), an agricultural byproduct, offers untapped potential as a biosurfactant source but suffers from inefficient extraction. We developed a pH-responsive platform integrating ultrasound-assisted alkaline three-phase partitioning (t-butanol/ammonium sulfate, pH 10) and acid-triggered precipitation (pH 4.5). This achieved 13.5 g saponins/100 g COSC in 30 min (92 % faster than Soxhlet) with 91 % t-butanol recovery. Acid-driven purification eliminated organic solvents, attaining 85 % purity versus conventional 70 %. Scalability was validated through pilot-scale trials (22.5-25 L working volume), achieving 12.7 g/100 g yield and 82 % purity. FTIR/HPLC analysis confirmed intact oleanane-type triterpenoids, correlating with superior functionality: critical micelle concentration of 1.0 % (vs. 3.0 % for conventional extract), 14-day emulsion stability, and enhanced bioactivities (DPPH IC₅₀ 1.23 g/L; MIC 1.29 g/L). Three breakthroughs were achieved: 1) pH-responsive efficiency-purity synergy, 2) closed-loop solvent reuse, and 3) acetone-free precipitation. This work provides a scalable, sustainable route to valorize agro-industrial residues into high-performance plant-based emulsifiers.