Abstract:
Microalgae being an aquatic photosynthetic organism, dissolved inorganic carbon (DIC) sources like bicarbonate (HCO3-) and carbonate (CO32-) are used in the present study for carbon fixation and sustain the biomass yield of Scenedesmus quadricauda (Turpin) Brébisson under nitrogen starved condition, to overcome the practical drawbacks associated with supply of gaseous form of CO2. S. quadricauda produces 198 mg/L lipid, with 7.14 fold reduction in biomass under nitrogen starved condition. Cell number, the primary parameter that determines the biomass yield, was maintained steadily (257×104 cells/mL) in the presence of Na2CO3 and NaHCO3. However, carbonate sources did not improve the total photosynthetic pigments. The total chlorophyll content showed drastic reduction of 0.091 to 0.022 mg/L in the presence of Na2CO3 (0.5 g/L). Similarly, the lower carotenoid value of 0.121 mg/L was recorded for sodium carbonate (0.5 g/L). Significant (P <0.0001) difference was observed for the carbonate source (primary factor) on biomass yield throughout the study period. Whereas the increasing concentration of individual DIC did not have any influence on the biomass yield under study conditions. Na2CO3 and NaHCO3 treated cultures exhibited monounsaturated fatty acid as dominant fraction as 84.70 and 84.28%, respectively, suggesting suitability of these fatty acids as biodiesel precursors.
