Enhanced selective extraction of bioactive components from Haematococcus pluvialis by using temperature-responsive microemulsions composed of deep eutectic solvents

Haematococcus pluvialis ( H. pluvialis) is rich in bioactive compounds. Traditional microemulsions (ME) can efficiently solubilize multipolar constituents, while fail to separate target products. In this study, a novel microemulsion (ME) composed of ionic liquid-based deep eutectic solvents (DES) was developed for multi-component extraction from H. pluvialis . The ME exhibited temperature-responsive UCST behavior, forming stable nanoparticles at 30 °C and demulsifying at 4 °C due to weakened intermolecular interactions and enhanced hydration effects at lower temperatures. Microstructure analysis revealed bicontinuous ME optimized co-extraction of hydrophobic and hydrophilic compounds. As compared with IL-based ME and conventional solvents, DES-ME achieved higher extraction efficiencies (carotenoids: 111.3 mg/g, lipids: 313.6 mg/g, proteins: 150.1 mg/g, carbohydrates: 26.98 mg/g). Post-extraction, cooling-enabled demulsification facilitated selective separation: carotenoids and lipids partitioned into the DES-rich phase (logK >0) due to strong CH-π/O interactions, while proteins migrated to the water-rich phase. DES-based ME significantly enhanced storage stability, delaying carotenoid degradation by encapsulating pigments in hydrophobic cores (ΔE = 7.89 vs. 9.71 for IL-based ME). The extract exhibited potent bioactivity of DPPH scavenging >95 % and exceptional antimicrobial effects against E. coli . Environmental assessment (GAPI score: 88) confirmed low toxicity, recyclability, and energy efficiency, positioning DES-based ME as a sustainable, high-performance alternative for extraction applications.