Integrated lipid production, CO2 fixation, and removal of SO2 and NO from simulated flue gas by oleaginous Chlorella pyrenoidosa.

CO2, SO2, and NO are the main components of flue gas and can cause serious environmental issues. Utilization of these compounds in oleaginous microalgae cultivation not only could reduce air pollution but could also produce feedstock for biodiesel production. However, the continuous input of SO2 and NO inhibits microalgal growth. In this study, the toxicity of simulated flue gas (15% CO2, 0.03% SO2, and 0.03% NO, balanced with N2) was reduced through automatic pH feedback control. Integrated lipid production and CO2 fixation with the removal of SO2 and NO was achieved. Using this technique, a lipid content of 38.0% DW was achieved in Chlorella pyrenoidosa XQ-20044. The lipid composition and fatty acid profile indicated that lipid production by C. pyrenoidosa XQ-20044 cultured with flue gas is suitable as a biodiesel feedstock; 81.2% of the total lipids were neutral lipids and 99.5% of the total fatty acids were C16 and C18. The ratio of saturated fatty acids to monounsaturated fatty acids in the microalgal lipid content was 74.5%. In addition, CO2, SO2, and NO from the simulated flue gas were fixed and converted to biomass and lipids with a removal efficiency of 95.9%, 100%, and 84.2%, respectively. Furthermore, the utilization efficiencies of CO2, SO2, and NO were equal to or very close to their removal efficiencies. These results provide a novel strategy for combining biodiesel production with biofixation of flue gas.

The synthesis of astaxanthin esters, independent of the formation of cysts, highly correlates with the synthesis of fatty acids in Haematococcus pluvialis.

The compositions and contents of astaxanthin esters and fatty acids in four types of Haematococcus pluvialis cells were studied by HPLC and GC-MS. Results showed that the synthesis and accumulation of astaxanthin was independent of the formation of cysts, but was highly correlated with the synthesis and accumulation of fatty acids, though it is an well known phenomenon that the accumulation of astaxanthin is usually accompanied by the formation of cyst. The red cysts contain more than 30% of fatty acids, with 81% of the unsaturated fatty acids. Taken together, besides a resource of astaxanthin, H. pluvialis would be a good resource of valuable fatty acids.