自絮凝微藻是一类细胞能够自发聚集的微藻的总称，其在培养结束时沉积在反应器底部而无需额外采收，有效降低了采收成本。氮是调控微藻生长代谢的重要因子。然而，氮对自絮凝微藻絮凝特性的影响及其作用机制尚不清楚，极大地限制了自絮凝微藻的应用。本项目拟重点分析氮源种类及其浓度对自絮凝微藻絮凝特性的影响，掌握氮调控下自絮凝微藻絮凝特性的变化规律，制定氮调控自絮凝微藻絮凝的控制策略。此外，鉴于胞外聚合物(extracellular polymeric substances, EPS)对微藻絮凝的重要性，对不同氮源及其浓度下自絮凝微藻的表面特征(疏水性和表面电势)、EPS的官能团、蛋白含量和二级结构以及氨基酸组成进行表征，分析表面特性的变化规律及其与EPS官能团和蛋白的关系，建立起氮、EPS与絮凝间的联系，揭示氮调控下EPS介导自絮凝微藻絮凝的机理。本研究可望为自絮凝微藻的应用提供一定的理论基础和技术支持。

Self-flocculating microalgae is a type of microalgae, which can aggregate together or form large particles by themselves. The aggregate can be then deposited at the bottom of the reactor at the end of the culture without extra harvesting, which effectively reduces the recovery cost. The nitrogen is important to microalgal growth, lipid metabolism and pollutants removal. Nevertheless, the flocculating characteristic of self-flocculating microalgae under nitrogen regulation is not clear, and the regulation mechanism behind self-flocculation is also unclear. These drawbacks limit a large-scale application of the flocculating technology to a certain extent. Consequently, the flocculating characteristic of self-flocculating microalgae under different nitrogen sources and concentrations will be analyzed and the variation regularity of flocculating characteristic will be grasped. Then the control strategy on flocculation of self-flocculating microalgae via nitrogen regulation will be formulated. Besides, considering the importance of extracellular polymeric substances (EPS) in the process of self-flocculation, surface characteristics (hydrophobicity and surface potential), functional groups, protein content, amino acid composition and protein secondary structure of self-flocculating microalgae under nitrogen regulation are analyzed. The change of surface characteristics and their relationships with functional groups and proteins of EPS are characterized to establish the relationship among nitrogen, EPS and flocculation. Finally, the self-flocculating mechanism mediated by EPS under the nitrogen regulation will be revealed. The project can provide some theoretical bases and technical supports for the future development and application of self-flocculating microalgae.