Effect of nitrogen limitation and irradiance on the biochemical composition of Haslea ostrearia

The marine diatom Haslea ostrearia is a valuable resource for biotechnological applications. However, its biochemical responses to crucial culture conditions, such as nitrogen availability and light intensity, still need to be explored. Therefore, this study evaluates the effects of nitrogen limitation and irradiance on the biochemical profile of H. ostrearia. Cultures were grown in two media: standard “f” medium (control) or “f” medium with a tenfold reduction in sodium nitrate concentration (1.7 × 10⁻⁴ M). These cultures were exposed to low (50 μmol m⁻² s⁻¹) or high (200 μmol m⁻² s⁻¹) irradiance and analyzed during exponential and stationary growth phases. Nitrogen control conditions with high irradiance resulted in the highest proteins (41 % based on organic dry weight, ODW), carbohydrates (8 % based on ODW), and pigments content, as well as the essential fatty acids EPA (19 % of total identified fatty acids, TIFA) and DHA (3 % of TIFA). Notably, under nitrogen-limited conditions combined with high irradiance during the stationary growth phase significantly increased lipids content (25 % based on ODW) and the proportions of palmitic (36 % of TIFA) and palmitoleic (30 % of TIFA) fatty acids. These findings emphasize the importance of optimizing nitrogen and irradiance conditions to enhance metabolite production in H. ostrearia, underscoring its potential in aquaculture, biotechnology, and functional foods industries.