Nitrate and ammonia: two key nitrogen sources for biomass and phycocyanin production by Arthrospira ( Spirulina ) platensis

Nitrogen plays a key role in the production of biomass and valuable pigments from Arthrospira platensis . The present research aimed to examine the effect of Zarrouk medium modified with six common nitrogen sources (NaNO 3 , KNO 3 , NH 4 NO 3 , NH 4 SO 4 , NH 4 Cl, and urea) on the biomass and phycocyanin production of the microalga. The medium supplemented with sodium and potassium nitrate resulted in the highest biomass production (~ 1180 mg L −1 ) and culture duration (18 days). The ammonia-based media resulted in the highest specific growth rate and phycocyanin production (118 mg L −1 ) but less maximum cell density and culture period because oversaturation of the media with ammonia causes cell toxicity. The highest phycocyanin content (113 mg g −1 ) was measured in the cells grown in NH 4 SO 4 -supplemented medium. In conclusion, the nitrate-based and the ammonia-based media are proposed for Arthrospira cultivation in closed photobioreactors and open pond systems with free gas exchanges with atmosphere, respectively.