Effective lipid induction and fractionation in Porphyridium purpureum: A sustainable nutraceutical and biofuel biorefinery

Red microalgae Porphyridium purpureum, a non-oleaginous species, demonstrates significant potential for sustainable bioactive metabolite production despite its naturally low lipid content. This study introduces a novel two-phase cultivation strategy to enhance lipid accumulation and polyunsaturated fatty acid (PUFA) yields. During the growth phase, white LED lighting promoted robust biomass production. In the induction phase, nitrogen deprivation, red light, high irradiance, melatonin (50 μM), and Fe₃O₄ nanoparticles synergistically enhanced lipid productivity, resulting in a higher biomass yield of 5.75 g/L and a lipid content of 26.73 %, representing a 1.45-fold increase. The PUFA content was significantly elevated, with arachidonic acid (87.21 mg/L), linoleic acid (298.19 mg/L), and gamma-linolenic acid (79.34 mg/L) showing notable increases. Pigment yields were optimized under white and yellow light, with C-phycocyanin (57.77 mg/g), allophycocyanin (65.67 mg/g), and phycoerythrin (14.45 mg/g) reaching peak levels. Furthermore, urea complexation effectively separated PUFA-rich (88.4 %) and SFA-rich (79.3 %) lipid fractions, supporting dual applications in nutraceuticals and biodiesel. This integrated strategy aligns with Sustainable Development Goal 3 (Good Health and Well-being), contributing to both health and environmental sustainability while advancing the microalgal biorefinery approach.