The stability in the C:N ratio indicates nitrogen saturation in the microalgal cultures (Otero et al., 1998). Higher nitrogen availability allowed microalgal cells to accumulate protein contents of 5.01 and 4.16 pg cell−1 at the renewal rates of 40 and 50% respectively,while only 3.41 pg cell−1 of proteinwas obtained with a renewal rate of 10%.