(R2 ¼ 0.86), 0.12 h1 and 12.83 mg/L (R2 ¼ 0.99), respectively as shown in Table 1. These results indicate that a low value of Ks suggests that the algae have a high uptake of nitrate for the cell growth. Ks corresponds to the substrate concentration, giving the halfmaximal of mmax. Among the four microalgae, I. galbana showed highest specific growth rate (mmax) of 0.23 h1 and lowest saturation constant (Ks) of 1.16 mg/L among those of other microalgae (Table 1).