Interaction of UV-C and glycerol during mixotrophic cultivation influenced B-Phycoerythrin, exopolysaccharides, and carbohydrates in Porphyridium purpureum

This study investigates the effects of various organic carbon sources—glycerol, glucose, molasses, and hydrolyzed molasses—and environmental conditions on the growth, carbohydrate content, exopolysaccharide (EPS) production, and phycobiliprotein synthesis in Porphyridium purpureum. Among the carbon sources tested, glycerol led to the highest growth rate, biomass productivity, and yields of carbohydrates and EPS due to its superior bioavailability and assimilation efficiency. Under autotrophic conditions, phycobiliprotein production peaked. Factorial analysis showed that the combined effect of UV-C light and glycerol supplementation produced the highest yields of pigment, EPS, and carbohydrates. Optimization via Response Surface Methodology (RSM) indicated that a UV-C light intensity of 5–6 mJ cm−2, along with a glycerol concentration of 800–900 mg L−1, maximized B-phycoerythrin (B-PE) production at 56 mg L−1, EPS at 102 mg L−1 day−1, and carbohydrates at 86 mg L−1. These findings demonstrate that glycerol supplementation combined with controlled UV-C exposure offers a practical strategy for enhancing biomass and metabolite production in P. purpureum, with promising applications for sustainable industrial-scale microalgal cultivation.