Effect of high CO2 concentrations on the growth and macromolecular composition of a heat- and high-light-tolerant microalga

Abstract

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-CO2 treatments (up to 20 %) on the growth of the alga and investigated the effects of different CO2 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 % CO2, 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 % CO2, respectively, indicating that this strain has significant tolerance to CO2. These results indicate that this strain is a promising candidate for use in biofixation of CO2 from the flue gases emitted by industries, and it also has a strong potential as a feedstock for value-added substances.