Screening and characterization of marine cyanobacteria for dairy farm wastewater treatment: Nodosilinea sp. E11 as a promising candidate for phycoremediation

Microalgae-mediated nutrient recovery offers a sustainable solution for high-salinity dairy farm wastewater treatment. Nonetheless, the intricate complexity and high variability in wastewater composition present substantial challenges to this process. This study investigated the growth performance of ten marine cyanobacterial strains in dairy farm wastewater and focused on two selected strains for their pollutant tolerance, wastewater treatment efficacy and value-added product synthesis. Results demonstrated that Nodosilinea sp. E11 exhibited superior performance compared to Synechocystis sp. C12-2 in wastewater remediation. Both strains displayed tolerance to most antibiotics and heavy metals present in the wastewater, while E11 displayed exceptional ammonium nitrogen (NH 4 + -N) resistance, maintaining viability at concentrations up to 250 mg/L. Notably, strain E11 achieved rapid biomass accumulation in the wake of wastewater quality fluctuations and demonstrated a high nutrient removal capacity, with elimination rates reaching 91.40 % for NH 4 + -N, 56.60 % for total nitrogen (TN), and 70.76 % for total phosphorus (TP). Component analysis revealed substantial temporal variations in E11 biomass composition. Peak protein content (123.06 mg/L) occurred on day 11, whereas maximum yields of total sugars (226.02 mg/L) and lipids (86.64 mg/L) were attained on day 19. Phycobiliproteins and palmitoleic acid were identified as high-value byproducts from E11 cultivation. By employing E11 for dairy wastewater treatment, an 11-days operational cycle is recommended for optimal performance balancing treatment efficiency and product recovery. The findings lay a theoretical foundation for the practical application of cyanobacteria in wastewater treatment and simultaneously open a new pathway for the resource utilization of cyanobacterial biomass. • The marine cyanobacterium Nodosilinea sp. E11 is a promising purifier of dairy wastewater. • High pollutant tolerance of Nodosilinea sp. E11 in dairy wastewater. • Nodosilinea sp. E11 achieves removal efficiencies of 56.60 % (TN), 70.76 % (TP), and 91.40 % (NH 4 + -N). • Dynamic shifts in biochemical composition found across growth phases in cyanobacteria. • Protein is the optimal transformation product of Nodosilinea sp. E11 for wastewater remediation.