Effects of initial density and light intensity on growth of microalgae Nannochloropsis oculata

Abstract

The microalgae were grown in 20 L plastic cans with three different initial density levels: 7.5 × 10⁴ (NT1), 8.5 × 10⁴ (NT2), and 9.5 × 10⁴ cells/mL (NT3). The results show that the treatment with a density of    8.5 × 10⁴ cells/mL provides the highest maximum density on the 10^th day of culture with a more stable equilibrium phase than the other two. The maximum density is (205.82  ±  0.18) × 10⁴ cells/mL for NT1, (267.24  ±  0.37) × 10⁴ cells/mL for NT2, and (259.18  ±  0.13) × 10⁴ cells/ mL for NT3. Nannochloropsis oculata reaches the highest extreme density ((283.27  ±  0,05) × 10⁴ cells/mL) on the 10th day of culture with a relatively stable, balanced phase at light intensity 3000 lux. Meanwhile, algae cultured at 4000 lux has a maximum density of (235.32  ±  0.11) × 10⁴ cells/mL, and the lowest is at 2000 lux, with the maximum density of algae of only (226.12  ±  0.20) × 10⁴ cells/mL.