A green microalga, Acutodesmus sp., a close relative of Acutodesmus deserticola , was isolated from the wastewater discharges of an oil refinery in India. This study examined the effects of light intensity, temperature, pH, and high-CO 2 treatments (up to 20 %) on the growth of the alga and investigated the effects of different CO 2 treatments on its macromolecular composition (protein, carbohydrate, and lipids). Under controlled laboratory conditions, the alga showed high growth rates over a wide range of light (up to 700 μmol photons m −2  s −1 ), temperature (up to 40 °C), and pH (5–10) conditions. In the stationary phase, the highest protein and carbohydrate content was found to be 71.52 and 40.72 % of dry weight at 5 and 15 % CO 2 , respectively. After 5 days of cultivation, the maximum dry weight biomass attained in these cultures was 1.149, 1.99, 1.75, and 1.65 g L −1 at 5, 10, 15, and 20 % CO 2 , respectively, indicating that this strain has significant tolerance to CO 2 . These results indicate that this strain is a promising candidate for use in biofixation of CO 2 from the flue gases emitted by industries, and it also has a strong potential as a feedstock for value-added substances.