Microalgae are an important potential feedstock for biodiesel production. Understanding the physiology of lipid biosynthesis in microalgae is pivotal to microalgal aquaculture management. A freshwater green microalga strain, UTEX 2219-4, was isolated from UTEX 2219 which was reported containing two strains. Its ITS sequences are closely related to those in the family of Scenedesmaceae in the GenBank. Nitrogen starvation, salt stress and osmotic stress greatly enhanced lipid biosynthesis in this strain, while combination of nitrogen deficiency and osmotic stress had the most dramatic effect. Chloroplast was condensed and photosynthesis efficiency declined about 50% after 3 days of nitrogen starvation. Chlorophyll degradation followed the same trend but was more severe than the reduction of photosynthesis efficiency. Oil body formation was not observed in the cells kept in the dark under nitrogen starvation, suggesting photosynthesis rather than autophagy is the major player in oil body formation. Under non-saturation levels of light intensities coupled with nitrogen starvation, the oil body formation under 150 £gmol/m2s light intensity was more efficient than that under 75 £gmol/m2s. DCMU blocked photosynthesis as well as oil body formation, supporting that the energy for oil body formation was mostly from photosynthesis rather than autophagy during nitrogen starvation.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第21811号 / 農博第2324号 / 新制||農||1066(附属図書館) / 学位論文||H31||N5183(農学部図書室) / 京都大学大学院農学研究科農学専攻 / (主査)教授 松村 康生, 教授 白岩 立彦, 教授 丸山 伸之 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM