Abstract

This study aimed to determine the optimum levels of sodium nitrate, sodium phosphate and sodium silicate suitable for growing Nannochloropsis oculata to achieve its best growth rate and quality. Results showed that the microalgae grown at sodium nitrate level of 112.5 mg L-1 achieved the best growth of 314.6 x 104 cells mL-1. A 50% increase in sodium phosphate concentration (7.5 mg L-1) compared with that of the control F/2 (5 mg L-1) exhibited the best microalgal growth and a density of 302.4 x 104 cells m L-1, while the microalgae in the control (F/2) reached a maximum density of 283.5 x 104 cells m L-1 at day 10 of culture. Similarly, with a 50% increase in Si content (45 mg/L) in the algal culture medium, the algal density reached 310.4 x 104 cells mL-1, which was higher than that of the nutrient medium F/2 (30 mg/L) that reached only a density of 280.5 x 104 cells mL-1. Levels of protein, lipid and carbohydrate accumulation in N. oculata also differed when increasing or decreasing sodium nitrate, sodium phosphate contents. Increasing the sodium nitrate levels by 50% from that of the control F/2 medium increased the protein (33.67%) and carbohydrate contents (8.54%) but decreased the lipid content (12.45%) compared with that of the nutrients in the F/2 (16.07%) medium. N. oculata attained high protein (33.96%) and carbohydrate (8.04%) contents when phosphorus content was increased to 50% (7.5mg L-1) compared to the control medium F/2 (5 mg L-1). However, increasing Si content did not significantly affect the nutritional composition of microalgae when compared to that of the F/2 nutrient medium.

(Source: https://www.proquest.com/scholarly-journals/effect-sodium-nitrate-phosphate-silicate-on/docview/2640799226/se-2?accountid=28030)