The Growth and Biochemical Composition of Nannochloropsis oculata under Influence of Different Nitrogen Sources for Aquaculture Live Food

This study aimed to investigate the influence of nitrogen from different sources on the growth and biochemical composition of the marine alga Nannochloropsis oculata. The effect of different nitrogen sources was addressed, viz. ammonium bicarbonate, ammonium sulfate, ammonium nitrate, ammonium chloride, urea, and sodium nitrate. The highest cell density (22.46 ×10⁶ cell mL^-1) of N. oculate, with a specific growth rate of 0.41 division day ^-1 was obtained with ammonium bicarbonate after eight days of incubation. Meanwhile, the total protein content was significantly increased by 38.28% with urea, although it showed the lowest content of lipid, carbohydrate. Ammonium nitrate showed the highest total content of lipids (43.67%), with a pronounced increase in total carbohydrate content (19.09 %) in sodium nitrate. Palmitic acid (C16:0) and stearic acid (C18:0) were the most abundant saturated fatty acids within all experimental treatments; whereas, palmitoleic acid (C16:1 ω7) and oleic acid (C18:1 ω9c) were the major monounsaturated ones. Both sodium nitrate and ammonium bicarbonate showed a higher content of eicosapentaenoic acid (C20:5 ω3) EPA, while docosahexaenoic acid (C22: 6 ω3) DHA and arachidonic acid (C20: 4 ω6) increased with urea. In conclusion, this study demonstrated the variation of growth, fatty acid profile, and biochemical composition in N. oculata, benefiting the production of microalgae for aquaculture live food.