Biochemical and nutritional profiling of Tetraselmis chuii and Nannochloropsis oculata cultivated in conventional F/2 and modified F/2-NPK media for aquafeed applications

Marine microalgae are promising sustainable ingredients for aquafeed applications because of their nutrient-rich biomass and capacity for controlled cultivation. However, reliance on conventional nutrient formulations remains a practical constraint for biomass production. In this study, Tetraselmis chuii and Nannochloropsis oculata were evaluated for growth, photosynthetic pigment accumulation, biochemical composition, and preliminary feeding performance when cultivated in conventional F/2 medium and a modified F/2-NPK medium in which selected F/2 macronutrient sources were replaced with a commercially available NPK fertilizer. Both species exhibited sustained growth under the two cultivation conditions. Peak biomass concentrations were 0.603 ± 0.008 and 0.570 ± 0.006 g L-1 for T. chuii and 0.577 ± 0.008 and 0.554 ± 0.010 g L-1 for N. oculata in F/2 and F/2-NPK media, respectively, with peak cell densities exceeding 21 × 106 cells mL-1 across treatments. Photosynthetic pigments accumulated progressively during cultivation. The modified F/2-NPK medium yielded the highest carbohydrate content in N. oculata (37.37 ± 0.31%) and the highest lipid content in T. chuii (9.42 ± 0.19%). Protein contents were 39.68 ± 0.10% and 36.82 ± 0.27% for T. chuii, and 36.20 ± 0.11% and 34.75 ± 0.23% for N. oculata cultivated in F/2 and F/2-NPK media, respectively. In a preliminary Artemia feeding assay, body length increased progressively and reached 9.12–10.10 mm by Day 20, indicating that biomass produced under both cultivation conditions supported Artemia growth under the tested conditions. As the feeding assessment was llength;to body length, these findings should be regarded as preliminary rather than as comprehensive validation of aquafeed efficacy. Overall, the modified F/2-NPK formulation supported the cultivation of both microalgal species while maintaining useful biomass and biochemical characteristics under laboratory conditions. Further nutritional characterization, controlled feeding trials in commercially relevant aquaculture species, scale-up evaluation, and techno-economic assessment are required to establish the broader applicability of the resulting biomass for aquafeed development.