Simultaneous use of urea and potassium nitrate for Arthrospira (Spirulina) platensis cultivation

Urea has been considered as a promising alternative nitrogen source for the cultivation of Arthrospira platensis if it is possible to avoid ammonia toxicity; however, this procedure can lead to periods of nitrogen shortage. This study shows that the addition of potassium nitrate, which acts as a nitrogen reservoir, to cultivations carried out with urea in a fed‐batch process can increase the maximum cell concentration (Xm) and also cell productivity (PX). Using response surface methodology, the model indicates that the estimated optimum Xm can be achieved with 17.3 mM potassium nitrate and 8.9 mM urea. Under this condition an Xm of 6077 ± 199 mg/L and a PX of 341.5 ± 19.1 mg L–1day–1 were obtained. Urea has been considered as a promising alternative nitrogen source for the cultivation of Arthrospira platensis if it is possible to avoid ammonia toxicity; however, this procedure can lead to periods of nitrogen shortage. This study shows that when potassium nitrate acting as a nitrogen reservoir is added to cultivations in a fed‐batch process with urea the maximum cell concentration and cell productivity of Arthrospira platensis is improved.