Work

Effects of nitrogen concentration on growth, fucoxanthin production, and fatty acid composition of the marine diatom Nitzschia sp

Year: 2026

Type: article

Abstract: Background Nitrogen availability strongly regulates growth and biochemical accumulation in marine diatoms, but the magnitude and direction of these responses are strain-specific. Optimizing nitrate supply may therefore provide a practical approach for improving biomass production and the accumulation of high-value metabolites in diatoms. Methods The effects of four sodium nitrate (NaNO₃) concentrations (0, 75, 150, and 300 mg L −1 ) on growth, biomass accumulation, total carotenoid concentration, fucoxanthin production, and fatty acid composition were investigated in the marine diatom Nitzschia sp. The standard f/2 nitrate concentration (75 mg L −1 NaNO₃) was used as the reference treatment, while 0, 150, and 300 mg L −1 represented nitrogen starvation, two-fold nitrate enrichment, and four-fold nitrate enrichment, respectively. Growth, biomass, carotenoid, and fucoxanthin parameters were monitored during 12 days of cultivation, and fatty acid composition was determined at the end of the cultivation period. Results Nitrate availability strongly affected growth and biochemical accumulation. The highest cell density (2.7 × 10⁶ cells mL −1 on day 9) and biomass productivity (0.068 ± 0.027 g L −1 d −1 on day 6) were obtained under 300 mg L −1 NaNO₃. Total carotenoid concentration reached its maximum of 2.08 mg L −1 on day 9 under 150 mg L −1 NaNO₃. Fucoxanthin content reached its highest value of 8.42 mg g −1 DW under 300 mg L −1 NaNO₃ on day 3, accompanied by the highest fucoxanthin productivity (0.689 ± 0.175 mg L −1 d −1 ). After 12 days, the highest total identified fatty acid content was obtained under 150 mg L −1 NaNO₃ (179.39 mg g −1 DW). EPA and DHA yields also reached their maximum values under 150 mg L −1 NaNO₃, at 25.12 and 3.52 mg g −1 DW, respectively. Conclusion Nitrate concentration differentially affected biomass production and biochemical accumulation in Nitzschia sp. A high nitrate supply of 300 mg L −1 NaNO₃ favored biomass accumulation and early fucoxanthin production, whereas 150 mg L −1 NaNO₃ favored total identified fatty acid accumulation and EPA/DHA yields. These findings demonstrate that nitrate supply should be optimized according to the target product and provide strain-specific baseline information for further optimization of high-value compound production in Nitzschia sp.

Source: Frontiers in Plant Science

DOI: 10.3389/fpls.2026.1936445