Effects of the availability of CO2 on growth, nutrient uptake, and chemical composition of the marine microalgae Chlorella sp. and Nannochloropsis oculata, two potentially useful strains for biofuel production.

Microalgae are among the most promising organisms for biofuel production. However, microalgaebased biofuels are not economically feasible and many efforts are in progress worldwide to achieve this goal. Here we report the effects of cultivation with input of pure CO 2 on the growth, nutrient uptake, and chemical composition of two marine microalgae: Chlorella sp. and Nannochloropsis oculata . Chlorella sp. grew more with addition of CO 2, but no difference was detected in the experiments performed with N. oculata . Both species showed an efficient consumption of dissolved nitrate and phosphate, and the nutrient uptake tended to be faster in the experiments with input of carbon dioxide. Carbohydrates were the most abundant substances in both species, and their concentrations increased dramatically in Chlorella sp. in the experiment with CO 2. Protein and lipid contents were relatively low in both microalgae, and these substances did not increase with the addition of CO 2. Results show that these species are not suitable for biodiesel production, considering their low lipid content under the culture conditions selected here. Present experimental conditions were not stimulating for the accumulation of lipids by the microalgae, and the effects of other parameters on the species should be tested in future studies.