Two-stage cultivation of Spirulina sp. LEB 18: a strategy to increase biomass productivity and synthesis of macromolecules

Microalgae have been highlighted in the production of biocompounds to apply in the food, pharmaceutical, and chemical sectors. Strategies in microalgae culture conditions, such as two-stage cultivation, can improve the synthesis of macromolecules of interest allied to increasing biomass productivity. The objective of this work was to evaluate the production of macromolecules [proteins, carbohydrates, polyhydroxybutyrate (PHB), and lipids] by Spirulina sp. LEB 18 cultivated in two-stage strategy. In the first stage of culture, modified Zarrouk medium was used, containing 100% of nitrogen (NaNO3, 2.5 g L-1) and 50% of carbon (NaHCO3, 8.4 g L-1). In the second stage, the culture medium was replaced by a medium containing nitrogen reduction (NaNO3, 0.25 g L-1) on the 5th, 10th, or 15th day. The nitrogen reduction the 5th day reached the highest lipid content (37.0%). To reach 58.1% of carbohydrates, cultivations must be conducted in a single stage for 20 days, using 10% of nitrogen source. The highest protein content was obtained with 100% nitrogen, on the 10th day of the first stage of cultivation (73.8%). The two-stage cultivation with the second stage on day 10 provides proteins (57.4%) on day 5, lipids (34.6%) on day 15, and PHB (29.6%) and carbohydrates (15.8%) on day 20, enabling operating microalgal biomass in a biorefinery system. Thus, two-stage strategy contributes to determining cultivation conditions that involve the optimization of macromolecules by Spirulina sp. LEB 18.

Automated summary

This study evaluated the ability of Spirulina sp. LEB 18 to produce macromolecules (proteins, carbohydrates, polyhydroxybutyrate, and lipids) under a two-stage cultivation strategy. The highest lipid content (37.0%) was achieved by reducing nitrogen on the 5th day of the first stage. To obtain the highest carbohydrate content (58.1%), cultivations should be conducted in a single stage with 10% nitrogen source. The highest protein content (73.8%) was obtained on the 10th day of the first stage with 100% nitrogen. The two-stage cultivation on day 10 provided proteins (57.4%) on day 5, lipids (34.6%) on day 15, and PHB (29.6%) and carbohydrates (15.8%) on day 20, enabling the operation of microalgal biomass in a biorefinery system.