Unveiling the potential of freshwater filamentous algae as a promising alternative source of essential fatty acids and bioactive carotenoids

Developing a sustainable and cost-effective food source enriched with essential fatty acids (EFAs) and other bioactive compounds, while minimizing the environmental impact, remains a significant challenge nowadays. In that regard, filamentous algae can be harvested more easily and at a lower cost compared to unicellular microalgae, making large-scale production of biomass and bioactive compounds more eco-friendly. The present study explores the potential of freshwater filamentous algae as a promising source for value-added products, particularly EFAs and bioactive pigments. The study involved an initial screening of 91 filamentous algae strains from the Microalgae and Zygnematophyceae Collection Hamburg (MZCH) to identify isolates with high growth rate. Eleven promising candidates were selected for further biochemical evaluation. Cell dimensions showed 5.8–117.2 μm length and 6.4–56.7 μm width. This variability in cell size enhances their suitability for specific applications, such as textile industry, where larger filaments can be directly utilized in producing bio-based fibers, yarns and fabrics. Among the studied algae, Oedogonium foveolatum and Spirogyra sp. #771 showed the highest biomass concentration (dry weight) of 0.70 and 0.67 g L⁻¹, respectively. Regarding value-added products, Hyalotheca dissiliens showed the highest carbohydrate content of 56.4 ± 2.32 % of dry weight (dw%), while Mougeotiopsis calospora showed the highest protein content of 48.0 ± 2.19 dw%. Klebsormidum nitens showed the highest total bioactive carotenoids (tBC) content of 11.5 ± 0.05 mg g⁻¹ dw and the highest tBC concentration of 4.03 ± 0.16 mg L⁻¹. Interestingly, Groenbladia neglecta stood out with the highest recorded lipid content of 34.4 ± 1.59 dw% and EFAs content of 14.3 ± 0.46 dw%. It also achieved a balanced ω-6/ω-3 ratio of 3.57 ± 0.03, which is optimal for dietary applications. The present study suggests G. neglecta under the mentioned growth conditions as a promising candidate for developing sustainable EFA-rich food sources, warranting further research and development.