Phycobiliproteins, a key component of phycobilisomes, are light harvesting proteins of some of the microalgae and seaweeds. Phycobilisomes are attached at the stroma side of thylakoid membrane made of glycerolipids and integral membrane proteins. The phycobiliprotein C-phycoerythrin (C-PE) is one of the light harvesting pigments present in cyanobacteria. Phormidium sp. isolated from Indian coast produces C-PE which is enhanced when grown in mixotrophic culture. Various exogenous carbon sources were evaluated for the mixotrophic culture in Phormidium sp. and glucose + peptone increased biomass productivity by 54% compared to the control (F/2 medium). C-PE enhancement with glucose + peptone at various COD concentrations and COD at 600 mg L⁻¹ (526.60 mg L⁻¹ glucose + 0.25 mg L⁻¹ peptone) produced higher C-PE content (7.36 mg g⁻¹ wet biomass). As C-PE is attached to thylakoid membranes made of glycerolipids, the effect of glycerol on C-PE at different concentrations was studied and the results showed that at 0.8 g L⁻¹ glycerol the C-PE content was enhanced to 11.52 mg C-PE g⁻¹ wet biomass. Phormidium sp. produced significantly (P < 0.001) more C-PE at 13.50 μmol photons m⁻² s⁻¹ than at other light intensities. Finally, Phormidium sp. that was grown mixotrophically with glucose, glycerol, and peptone at 13.50 μmol photons m⁻² s⁻¹ produced C-PE efficiently. Using C-PE as a food colorant will be an effective way of addressing health-related problems associated with chemical food colors, which are commonly used in the food industry.

Graphical Abstract