The production of fucoxanthin and fatty acids in Conticribra weissflogii has been examined, but the role of elements like phosphorus in their mutualistic interactions is not well understood. To fill this gap, our study utilized potassium dihydrogen phosphate (KH₂PO₄) as a source of phosphorus to examine its impact on the synthesis of fucoxanthin and fatty acids in C. weissflogii. Our findings revealed that at a phosphorus concentration of 10 mg L⁻¹, the cell density (9.5 × 10⁵ cells mL⁻¹), carotenoid concentration (1.67 mg g⁻¹), fucoxanthin concentration (0.91 mg L⁻¹), and fucoxanthin content (1.33 mg g⁻¹) were maximized. Additionally, at a phosphorus concentration of 20 mg L⁻¹, cell dry weight (0.76 ± 0.08 g L⁻¹), total fatty acid content, saturated fatty acids, and unsaturated fatty acids were all at their highest levels, making this concentration optimal for EPA accumulation. In conclusion, manipulating the phosphorus concentration can enhance the levels of fucoxanthin and unsaturated fatty acids in C. weissflogii, offering valuable insights into the co-production of these two high-value compounds within this species.

This study assessed the effects of different intensities of broad-spectrum white LED light (PAR range: 415–748 nm) on growth, fucoxanthin accumulation, and fatty acid composition of Isochrysis galbana. This study classified light intensity into three categories based on the white LED light source: high (HL, 150 μmol·m⁻²·s⁻¹), medium (ML, 80 μmol·m⁻²·s⁻¹), and low (LL, 30 μmol·m⁻²·s⁻¹). The results showed that biomass concentration was optimized under high light intensity (HL, 150 μmol·m⁻²·s⁻¹), whereas low light (LL, 30 μmol·m⁻²·s⁻¹) yielded the highest fucoxanthin concentration (71.15 mg/L on day 12) and the only positive volumetric fucoxanthin productivity (3.14 mg/L/d) among the three treatments tested. The results further showed that low light (LL, 30 μmol·m⁻²·s⁻¹) produced maximum cell density (10.08 × 10⁶ cells/mL) and the most polyunsaturated fatty acids (PUFAs), particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which constituted 1.93% and 22.47% of total fatty acids, respectively. This study demonstrates that low-intensity (LL, 30 μmol·m⁻²·s⁻¹) white LED light supports the maximum co-production of valuable metabolites in I. galbana, establishing a scientific basis for scaling up I. galbana cultivation for nutraceutical and aquafeed applications.