海洋微拟球藻（Nannochloropsis）全细胞生物转化制备生物柴油之机制研究

Although microalgae represents a promising alternative feedstock for biofuels, the current hydrothermal- and solvent-based lipid extraction and conversion systems and processes are neither cost-effective nor energy-efficient. As a result, the commercial process for the production of algal biodiesel has been greatly impeded due to the high cost and lack of effective middle- and downstream processes. In the proposed research, Nannochloropsis will be selected as the study material for bioconversion investigations. Structures together with the biological compositions of cell walls will also be investigated intensively at the subcellular and molecular levels. In addition, the regulation mechanisms associated with influences of cell life cycle and culture conditions will be further addressed. Based on the above results, promising enzymes related to the cell wall degradations and hydrolysis will be tested and screened from commercial sources. Response mechanisms of cell wall TLS structure to enzymes will be evaluated by investigating the hydrolysis processes and their hydrolysis products with different enzymes, as well as the changes of cell wall ultrastructures. In the studies related to lipase conversion of algal oils, the influences of solvents and ion liquids on the secondary structures and lipase activities of both free and immobilized lipases will be systematically investigated. Mechanisms underline the conversion of different kinds of algal lipids (phospholipids, glycolipids, free fatty acids, triglyceride, diacylglycerol, monoacylglycerol and so on) with lipases will be further revealed and the dynamics of the conversion reactions with both specific and nonspecific lipases will also be studied. Finally, based on the mechanism studies in the structure and compositions of cell walls, enzymatic hydrolysis and degradation of cell walls and lipase-based conversion of algal lipids into biodiesel, comprehensive conversion mechanisms associated with biochemical conversion of whole algal biomass into biodiesel will be revealed in this proposed study. The proposed study shows great potentials to reduce the costs in middle and downstream processes of algal biodiesel productions such as harvesting, drying, oil extraction, oil refining, transesterification and so on. The implement of the proposed studies will greatly accelerate the commercialization and industrialization of algae-based biodiesel productions, which will have strategic significance for energy security in our country.

本研究拟针对我国能源微藻产业化进程中将面临的中下游转化成本过高这一瓶颈问题，选用海洋微拟球藻作为研究对象，深入研究其细胞壁的结构、生物质组成，从亚细胞和分子水平解析培养条件和细胞生命周期对其细胞壁合成的调控作用等相关生物学机制；通过遴选微拟球藻细胞壁的高效降解酶，研究不同功能的酶对其细胞壁TLS层状结构的作用机制，考察降解过程中降解产物的动态变化，进一步阐明微拟球藻细胞壁对水解酶的响应机制和降解机理；通过研究不同溶剂体系对酯酶的蛋白质二级结构的影响以及特异性酯酶和非特异性酯酶对微藻原油的动态转化机制，探明酯酶结构与催化效应之间的内在联系，揭示酯酶催化微藻原油制备生物柴油的转化机制。在此基础上，阐明微拟球藻全细胞转化制备生物柴油的综合机理和过程。研究结果将为发展微藻生物能源的新型转化技术提供理论依据，同时将对我国推进以微藻生物柴油为代表的新能源的发展、保障国家的能源战略安全有重要指导意义。

本研究针对海洋微拟球藻全细胞转化制备生物柴油转化过程中所存在的技术难点，探索了微拟球藻的最适培养条件，研究了海洋微拟球藻的生物质组成；考察了壳聚糖酶、果胶酶、蛋白酶、纤维素酶、淀粉酶等细胞壁降解相关生物酶对微藻细胞壁的破碎效果，并优化了复合酶制剂催化破碎细胞壁提取微藻油脂的方法；探究了溶剂作用下酯酶催化转化微藻原油制备生物柴油的效率，并优化酶促反应条件。研究成果为微藻生物质培养、微藻破壁提油以及微藻原油转化提供了一套全新的高效、节能、环保的生产技术，为发展微藻生物能源提供了理论依据。本研究获得了多项发明专利，并有关键研究成果发表在微藻能源领域国际著名刊物上。