Study On Carbon Fixation And Lipid Accumulation Of Scenedesmus Dimorphus Under Simulated Microgravity

The energy shortage and global warming are two serious problems facing human society today.Developing renewable energy and reducing carbon emission are of great significance to human sustainable development.Microalgae can efficiently absorb carbon dioxide and accumulate lipid,and has great potential for energy storage and mitigation of carbon dioxide emission.Scenedesmus has the advantages of fast growth rate and high lipid content,and therefore it can be considered as one of the important candidates for energy microalgae.In this work,Scenedesmus Dimorphus were cultured by carbon dioxide aeration in simulated microgravity environment.Firstly,the growth rate of Scenedesmus Dimorphus cultivated under bubbling of different concentrations of carbon dioxide were measured,then the influence of simulated microgravity on the growth of Scenedesmus Dimorphus with carbon dioxide aeration was investigated.The growth rate,lipid accumulation and carbon fixation rate of Scenedesmus Dimorphus cultured under different conditions were determined.The main experimental conclusions are as follows:?1?Scenedesmus Dimorphus grew well under the range of experimental carbon dioxide concentration?0-50%,v/v?.The growth rate and total organic carbon content of the Scenedesmus Dimorphus increased significantly after bubbling of extra carbon dioxide.The lipid content of the algae increased with the increasing of concentration of carbon dioxide.The main lipid constituents of Scenedesmus Dimorphus were fatty acids 16:0,16:4,18:2 and 18:3,and the content of unsaturated fatty acids increased after carbon dioxide was bubbled.The chlorophyll content of Scenedesmus Dimorphus cultured under carbon dioxide aeration was significantly higher than that without bubbling of extra carbon dioxide,and the chlorophyll content increased with the increasing of concentration of carbon dioxide.Carbon dioxide has significant effect on the morphology of Scenedesmus Dimorphus cell,and the average diameter and the cell aspect ratio of the algae increased.?2?Under simulated microgravity the growth rate of Scenedesmus Dimorphus cultivated with carbon dioxide aeration was significantly higher than that of the condition without bubbling of extra carbon dioxide,and the total organic carbon content increased when carbon dioxide was bubbled.The lipid content of Scenedesmus Dimorphus in carbon aeration groups was higher than that of the control group.The main lipid constituents of the algae cells were fatty acids 16:0,18:2 and 18:3,and the content of unsaturated fatty acids decreased after carbon dioxide was introduced.The chlorophyll content decreased with the increasing of concentration of carbon dioxide.The maximum photochemical yield of PSII of Scenedesmus Dimorphus increased when the algae was cultivated under simulated microgravity,or with 10%carbon dioxide aeration.The ETR_?max?of Scenedesmus Dimorphus decreased under the simulated microgravity,while the ETR_?max?increased under the conditions of carbon dioxide aeration.The average diameter of Scenedesmus Dimorphus decreased,but the cell aspect ratio of the algae increased under microgravity conditions.?3?Compared with the algae cultivated under normal condition,the growth rate,carbon fixation rate and lipid production of Scenedesmus Dimorphus increased significantly under simulated microgravity and carbon dioxide aeration.