Nitrogen concentration influences growth performance and biochemical composition of the endosymbiotic dinoflagellate...

Endosymbiotic dinoflagellates are promising sources of biomolecules with high biotechnological potential. However, knowledge on their cultivation strategies and physiological responses to nutrient modulation remains limited. This study evaluated the effects of different nitrogen concentrations-resulting in nitrogen-to-phosphorus (N: P) ratios of 0:1, 7:1, 14:1, and 28:1-on the growth performance and biochemical composition of D. glynnii. Experiments were conducted in two consecutive cultivation rounds (C1 and C2), each comprising three biological replicates per treatment, to assess temporal stability and metabolic adaptability. Results indicated that D. glynnii was unable to sustain growth in the absence of nitrogen. The highest growth rate (0.19 ± 0.01 day⁻¹), biomass concentration (753.33 ± 14.14 mg L⁻¹), and protein yield (9.89 ± 0.19 mg L⁻¹ day⁻¹) were observed at the 28:1 ratio. Protein content increased proportionally with nitrogen availability, reaching 31.51 ± 0.15% of dry weight at 28:1. Crude lipid content also peaked under this condition (7.27 ± 0.65% of dry weight). Although some variability between independent experimental runs was observed, particularly under nitrogen deprivation, the overall trends were consistent and ecologically relevant. These findings underscore the key role of nitrogen availability in modulating both growth and biochemical composition in D. glynnii. While higher N: P ratios favored biomass productivity, the data also suggest that phosphorus became limiting at the later stages of the experiment under N-rich conditions. This highlights the importance of balancing N and P supply in intensive cultivation. Further studies are recommended to investigate nutrient uptake dynamics, optimize stoichiometric ratios, and explore long-term adaptive responses.