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

## TL;DR

A new pH-responsive system efficiently extracts high-purity saponins from Camellia oleifera waste, offering a fast and sustainable method for producing plant-based emulsifiers.

## Contribution

A pH-responsive, solvent-efficient biorefining system that combines ultrasound and acid-triggered purification for high-yield saponin extraction.

## Key findings

- Extracted 13.5 g saponins/100 g Camellia oleifera seed cake in 30 min, 92% faster than traditional methods.
- Achieved 85% purity without organic solvents and 91% t-butanol recovery in a closed-loop system.
- Purified saponins showed 1.0% critical micelle concentration and 14-day emulsion stability.

## Abstract

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.

•UATPP-AP extracts 13.5 g/100 g saponins in 30 min (92 % faster).•Closed-loop t-butanol recycling (91 %) with solvent-free crystallization (85 % purity)•Scalable process maintains 82 % purity, 12.7 g/100 g yield at 22.5–25 L vol.•Purified saponins achieve 1.0 % CMC (vs 3.0 % conventional) & 14-day stable emulsions.•pH-responsive purification retains dual antioxidant/antimicrobial saponins.

UATPP-AP extracts 13.5 g/100 g saponins in 30 min (92 % faster).

Closed-loop t-butanol recycling (91 %) with solvent-free crystallization (85 % purity)

Scalable process maintains 82 % purity, 12.7 g/100 g yield at 22.5–25 L vol.

Purified saponins achieve 1.0 % CMC (vs 3.0 % conventional) & 14-day stable emulsions.

pH-responsive purification retains dual antioxidant/antimicrobial saponins.