Optimizing growth and biochemical composition in Isochrysis maritima and Chaetoceros constrictus: Manipulation of nitrogen and temperature

The regulation of biochemical composition in microalgae by nitrogen enrichment and temperature adjustment is critical for ensuring culture quality and yield. This study examined the influence of nitrogen concentrations and temperature levels on the growth and biochemical composition of Chaetoceros constrictus and Isochrysis maritima to optimize culture performance. Microalgae were cultivated using Walne’s medium supplemented with nitrogen concentrations of 42, 80, and 297 mg/L, under controlled temperatures ranging from 15°C to 32°C. Growth rates were calculated; protein, lipid and fatty acids composition of the microalgae were analysed. After 18 days, maximum cell densities were recorded at 9.80 × 10 6 cells/mL in I. maritima and 9.96 × 10 6 cells/mL in C. constrictus, at nitrogen concentrations of 42 mg/L and 80 mg/L, and temperature at 25°C. Highest protein and lipid were observed at nitrogen concentration of 80 mg/L and 297 mg/L, with temperatures between 20°C and 25°C for both microalgae. The highest concentrations of saturated, monounsaturated, and polyunsaturated fatty acids were achieved at 80 mg/L under temperatures of 25°C to 28°C. Overall, optimal nitrogen enrichment (80 mg/L) and temperature (25°C) significantly influenced biochemical composition, enhancing fatty acid, protein, and lipid production, and improving microalgal biomass yield for aquaculture.