The Effects of Nitrogen Concentration on Growth, Protein, and Lipid Content of Euglena sp. isolated from Mataram Irrigation Canal, Indonesia

The increasing demand for sustainable food and bioenergy sources has intensified interest in microalgae such as Euglena sp., which produce diverse primary metabolites with biotechnological value. This study aimed to evaluate how nitrogen availability regulates growth performance and metabolic allocation in Euglena sp. isolated from the Mataram Irrigation Canal, Yogyakarta, Indonesia. Cultures were grown for 14 days under four ammonium sulfate ((NH4)2SO4) concentrations: 250 mg/L (¼N), 500 mg/L (½N), 1000 mg/L (control), and 2000 mg/L (2N). Growth was measured spectrophotometrically at 680 nm. Protein and lipid contents were determined using the Bradford and Bligh–Dyer methods, respectively. The highest specific growth rate (8.50 × 10-3 h-1) and protein content (0.368 g/L) were achieved at 2N treatment, which also supported high biomass production. Furthermore, the highest average biomass was observed in the control (0.373 g/L) and 2N (0.335 g/L) groups, indicating that nitrogen sufficiency promotes anabolic metabolism and cellular proliferation. In contrast, nitrogen limitation (¼N treatment) significantly enhanced lipid accumulation (0.556 g/L) but suppressed growth, reflecting a metabolic shift toward carbon storage. These findings suggest that nitrogen concentration can be strategically manipulated to direct metabolic outputs in Euglena sp., providing a basis for optimizing cultivation systems tailored for protein-rich biomass or lipid-based bioenergy production.