A Low-Cost Nitrogen Strategy for High-Value Protein and Pigment Production from Arthrospira platensis

Nitrogen sources significantly affect the growth and biochemical compositions of Arthrospira platensis, especially protein and pigments. Urea has emerged as an alternative to sodium nitrate, NaNO3, a conventional nitrogen source for large-scale cultivation, due to its lower cost. In addition, urea assisted cells in tolerance to high temperatures. This study aimed to investigate the effects of combining nitrate and urea on growth, protein and pigment accumulation in A. platensis C1 as a potential strategy for cost-effective production. A. platensis C1 was cultivated in the standard Zarrouk’s medium with either combined N-sources (14.5 mM Nitrate-N + 14.5 mM Urea-N) or standard medium (29 mM Nitrate-N) under 100 μmol photons m−2 s−1 at 35 °C. After 4 days of cultivation, cells grown with the combined nitrogen sources exhibited growth performance comparable to the standard medium (1068 ± 0.082 mg L-1) with biomass production of 1145 ± 0.065 mg L-1. Protein content reached 582.71 ± 45.32 mg L-1 DW, comparable to the control (512.41 ± 75.97 mg L-1). In terms of pigments, the chlorophyll content levels in cells cultivated with the combined nitrogen sources (17.14 ± 0.5 mg L-1) remained similar to the control (17.95 ± 0.83 mg/L). Interestingly, phycocyanin content (130.21 ± 8.85 mg L-1) was significantly higher than the control (109.67 ± 13.14 mg L-1). These results indicate that combining urea with nitrate is a promising strategy for A. platensis C1, highlighting a potential benefit in protein and pigments accumulation without compromising growth. This approach offers a cost-effective cultivation method for improving high-value compounds in algal biomass.