Seawater as Nutrient and Water Sources for Spirulina Production

Spirulina is recognized as a superfood due to its high nutrient contents such as protein, essential amino acids, vitamins, essential fatty acids, and nutraceutical pigments. Although the demand for using Spirulina as human and animal food supplements increases significantly, the production cost also increases. This study aimed to investigate a low-cost medium for Spirulina production by using seawater as a nutrient source and freshwater. Arthrospira (Spirulina) platensis was cultivated in both standard Zarrouk’s medium (control) and modified Zarrouk’s medium containing NaHCO3 (4 or 16.8 g L -1 ), K2HPO4 (0.5 g L -1 ), NaNO3 (2.5 g L -1 ), FeSO4. 7H2O (0.01 g L -1 ), EDTA-Na (0.08 g L -1 ) and seawater (varied 5 – 20% (v/v)). The growth cultures were daily measured for 7 days before harvesting the cells for biochemical analysis. The results showed that the 20% seawater could be utilized to substitute some chemicals and fresh water in Zarrouk’s medium. A. platensis grew in the medium containing seawater had specific growth rates ranging from 0.0304 to 0.0434 h-1 . Among the modified Zarrouk’s medium, the formula of 15% seawater and 16.8 g.L-1 NaHCO3 gave rise to the highest biomass yield and biomass productivity of 2.395 ± 0.126 g L -1 and 0.311 ± 0.017 g L-1 d -1 , respectively. This condition increased carbohydrate content in the cells by more than 2-fold compared to control. The results suggested that seawater can be used as both a chemical alternative and a source of water for Spirulina cultivation. This is a promising step in reducing the use of certain chemicals that have a direct impact on production costs.