Abstract
Phycobiliproteins and microalgal exopolysaccharides serve as natural pigments and functional additives in food applications. Current production primarily relies on multicellular algae, where yields are constrained by challenges in achieving high-density cultivation. This study investigated photoperiod effects on growth and production of phycobiliproteins and polysaccharides in two unicellular red algae (Porphyridium purpureum and Porphyridium aerugineum). Results demonstrated that short photoperiods enhanced the accumulation of core phycobiliproteins, specifically by increasing phycoerythrin in P. purpureum to a maximum of 30.5 ± 0.8 mg/g DW and phycocyanin in P. aerugineum to 41.9 ± 0.2 mg/g DW. Conversely, long photoperiods promoted biomass accumulation, yielding peak phycoerythrin production (140.6 ± 0.9 mg/L) in P. purpureum and phycocyanin (137.7 ± 1.2 mg/L) in P. aerugineum at day 12. Both species exhibited superior exopolysaccharide production under long photoperiods, though P. purpureum showed significantly higher productivity (898.7 ± 41.0 mg/L at day 20). These findings offer strategic solutions for sustainable production of food-grade pigments and polysaccharides through optimized unicellular algal cultivation.