Nutrient balance for enhanced recovery of stressed Spirulina platensis

The failure of mass production of Spirulina plateaus can be attributed to an imbalance of nutrients (C:N) and an increase in accumulated sodium ions, coupled with the traditional harvesting process. The current study aims at the recovery of stressed and red cultures of Spirulina platensis as well as enhanced phycocyanin accumulation. The stressed Spirulina platensis cultures were obtained from a local Egyptian Spirulina production farms, which were further subjected to water analyses after removing the Spirulina biomass. Optimization was performed within 300-ml water path photobioreactor. Spirulina platensis samples were incubated with Zarrouk medium comparing with those modified using ammonium bicarbonate or ammonium acetate instead of sodium bicarbonate. Continuous batching was performed every 12 days during three sequenced batches. Growth measurements (dry weight and pigments) were performed along the incubation time. It was found that carbon content of the growth medium seems to be more effective in Spirulina growth and biomass characteristics. Under different carbon sources, acetate resulted in the maximum dry weight of 1.48 g·l^-1 and recovery percentage of 463.3%. Such effect was extended along the different incubation batches. Various carbon concentrations revealed that moderate concentration of carbon in the form of acetate (0.699 g·l^-1) leads to the maximum growth under the same nitrogen content. A similar trend was observed with chlorophyll and phycocyanin accumulation, while carotenoids showed the opposite manner.