Continuous and pulse feedings of urea as a nitrogen source in fed-batch cultivation of Spirulina platensis

Spirulina platensis was autotrophically cultivated by fed-batch addition of urea as a nitrogen source. Continuous and pulse feeding regimes of this nitrogen source (time intervals of 24h) were compared using a constant mass flow rate. Both series of experiments were carried out at three different temperatures (25, 28 and 31°C) and total times of urea addition (12, 15 and 18 days), according to a 22 simple factorial design, and the effects of these variables on the nitrogen-to-cell conversion factor and cell productivity were verified by analysis of covariance (ANCOVA). The intermittent addition of urea yielded results similar to those obtained by the continuous feeding, therefore, the former operation mode would be preferable to reduce the production costs of this cyanobacterium in large-scale facilities.