Recirculation of Saline Concentrate in Spirulina Cultivation: A Promising Strategy for High Production of Biomass and Biomolecules in Semiarid Regions

Desalination concentrate (DC) is a residue from desalination plants in semiarid regions, and it is promising for microalgae cultures. Its effects have been evaluated in a previsions study involving Spirulina sp. LEB 18 cultures grown in a medium containing 100% DC, supplemented with 25% Zarrouk nutrients, and without reuse. In the present study, Spirulina sp. LEB 18 was cultivated in the recycled saline concentrate medium from the previous experiment over three consecutive cycles using raceways. The recycled DC achieved a maximum biomass production of 3.77 g·L−1, surpassing the control production (3.45 g·L−1), and demonstrated high resistance to elevated environmental temperatures, reaching 42.80 °C. Protein levels (≤37%) containing all essential amino acids (~40% of total proteins) and fatty acids with relevant impacts on health were reached. Using up to three DC cycles for Spirulina sp. cultivation can contribute to the valorization of this residue and add viability to semiarid regions for biomass production with adequate nutritional composition for supplementation of humans and animals.