Influence of Nitrogen to Phosphorus Ratio and CO2 Concentration on Lipids Accumulation of Scenedesmus dimorphus for Bioenergy Production and CO2 Biofixation

Abstract The potential of Scenedesmus dimorphus microalgae for CO 2 biofixation and lipid biosynthesis for bioenergy applications was evaluated in this study. Batch experiments were conducted using synthetic tertiary municipal wastewater samples at several nitrogen to phosphorus (NP) ratios (1 : 1 to 8 : 1) and CO 2 concentrations (∼0%, 2%, 4%, and 6% CO 2 in supplied air). Scenedesmus dimorphus was cultivated for 25 days and the growth is highly dependent on the CO 2 concentration and the NP ratio. An NP ratio of 2 : 1 produces a biomass yield of 733 mg/L when the microalga culture was supplied with air enriched with 2% CO 2 . The maximum CO 2 biofixation rate of 49.6 mg L −1 d −1 is at an NP ratio of 8 : 1 with 4% CO 2 . A colorimetric technique depending on sulpho‐phospho‐vanillin (SPV) was utilized for the determination of the intracellular lipid content. The highest lipid content of 31.6% as the dry weight of the biomass is at an NP ratio of 1 : 1 and 6% CO 2 . These results indicate that supplementation of suitable CO 2 with favorable NP ratio has a considerable effect on lipid accumulation in the microalgae Scenedesmus dimorphus biomass.