Cultivation strategy optimization and pilot-scale production of Spirulina subsalsa grown in seawater and monosodium glutamate wastewater.

Spirulina subsalsa represents a promising candidate for commercial production. Yet, due to its unique pattern of attached growth followed by upward flotation, there is an urgent need to find a suitable cultivation strategy and achieve scale-up. In the low-cost medium of seawater plus monosodium glutamate wastewater, this study initially investigated the influence of aeration rate (0, 0.3, 0.6 L/min) and reactor geometry (D₂₄d_4.5, D₁₈d₈, D₁₂d_18, D: diameter, cm; d: depth, cm) on microalgal growth, indicating that Spirulina subsalsa was suited for culturing in non-aerated, wide-shallow reactors. Then, in the single plastic reactor, diverse depths (2.25, 4.50, 9.00 cm) and surface areas (1000, 2000, and 3000 cm²) for culturing Spirulina subsalsa were optimised to 4.5 cm and 2000 cm². Subsequently, a pilot-scale cultivation system with a volume of 162 L was constructed, adopting a semi-continuous culture mode. The average dry mass productivity was 0.12 g/L/d and 816.48 g of algal powder was harvested within 41 days. The mean contents of protein, carbohydrate and lipid were respectively 46.50%, 14.95% and 10.87%. Moreover, economic analysis demonstrated that the cost of produced algal powder was 8.30 USD/kg. In the future, Spirulina subsalsa has the potential to be developed into multiple products.