Integrated biorefinery of Limnospira (Arthrospira) platensis: Recycling cultivation medium and biosorption of endocrine disruptors from water

Abstract

Microalgae-based systems are increasingly recognized as scalable platforms for producing high-value bioproducts while addressing water pollution, including emerging contaminants. However, large-scale production is often constrained by high operational costs. This study evaluated biomass production of the cyanobacterium Limnospira (Arthrospira) platensis over two consecutive cultivation cycles, with the culture medium from the first cycle recycled in the second. Mediumrecycling reduced freshwater and nutrient inputs without compromising biomass productivity. Biomass from both cycles exhibited high protein (59.8 ± 1.9% in cycle 1; 52.6 ± 2.0% in cycle 2) and carbohydrate contents (29.3 ± 1.8% and 39.0 ± 2.4%, respectively), supporting diverse valorization pathways. First-cycle biomass is suitable for high-value applications such as nutraceuticals, while second-cycle biomass was evaluated as a low-cost biosorbent for removing 17α-ethinylestradiol (EE2), a pseudo-persistent endocrinedisruptorfrequently found in aquatic ecosystems. Biosorption assays achieved ∼70% EE2 removal at 30 μg·L⁻¹ within 7 h using 0.6 g·L⁻¹ of biomass (biosorbent). Kinetics followed a pseudo-second-order model (R² = 0.98), and equilibrium data fitted the Freundlich isotherm, with a maximum adsorption capacity of 251.28 μg·g⁻¹. These results demonstrate that cultivation medium recycling can simultaneously reduce resource consumption and enable cascade biomass valorization, providing a scalable approach aligned with circular bioeconomy principles and sustainable tertiary wastewater treatment.