Integration of ultrasonication with liquid triphasic flotation system for the extraction of phycocyanin and protein from Spirulina platensis

BACKGROUND: Growing demand for natural pigments and vegan proteins has intensified interest in Spirulina platensis. However, the conventional extraction method caused phycocyanin degradation in Spirulina platensis, often resulting in low yields of the recovered compounds. RESULTS: A hybrid process that couples ultrasonication with a liquid triphasic flotation system (LTFS) was developed and optimised by one-variable-at-a-time (OVAT) experimentation. Optimum conditions, 90% (v/v) t-butanol, 200 g L⁻¹ ammonium sulphate, 10% (w/v) phosphate buffer, 4% (w/v) biomass loading, 20 min process duration at 40 °C, raised protein separation efficiency to 77.3% ± 1.1%, protein recovery to 79.2% ± 0.9%, and phycocyanin recovery to 90.3% ± 1.2%. SEM images confirmed cell-wall disruption after sonication, FTIR spectra revealed intact amide bands, and SDS-PAGE showed a predominant 17 kDa phycocyanin sub-unit with minimal fragmentation. CONCLUSION: Integrating ultrasonication with LTFS provides a rapid, energy-lean, and scalable route for simultaneously isolating high-purity phycocyanin and protein from S. platensis, overcoming the time, energy, and yield penalties of conventional methods. The platform is readily adaptable to other cyanobacterial feedstocks and supports the development of cost-effective natural-colourant and protein ingredients for food, cosmetic, and nutraceutical markets.