异养型能源微藻筛选及其利用挥发性脂肪酸产油的代谢调控机制

In order to reduce the production cost of microalgae, the use of waste to produce biomass energy seems to be a useful attempt in the field of environmental protection and energy development. Using the volatile fatty acids (VFAs) from the anaerobically digested effluent to produce microalgae can achieve high efficiency and low cost biodiesel production, which is of great significance to solve the high cost problem that hampers the large scale production of microalgae for biodiesel. Whether the waste can be used effectively is a key issue in determining whether secondary pollution is produced after waste treatment and whether microalgae produce lipid efficiently. The aim of this project is to screen high oil-yielding microalgae from heterotrophic environment, to study the effects of environmental factors on the lipid accumulation properties of the dominate algae species and the utilization rate of volatile fatty acids (VFAs) by the algae; to explore the optimal environmental conditions for effective use of volatile fatty acids (VFAs) and efficient lipid production by the dominate algae species; and to reveal the relationship of the growth rate, substrate utilization rate and the distribution of carbon flow of dominate algae species, at last to elucidate the metabolic regulation mechanisms of volatile fatty acids on lipid synthesis in high oil-yielding microalgae selected from heterotrophic conditions. It will provide scientific and technical support to achieve the advance use of waste and the efficient energy production by microalgae. The success of the project will achieve the combination of waste treatment and energy production. It will realize the win-win situation of purifying the environment and reducing the cost of energy production, which has important theoretical and practical significance.

为降低微藻生产成本，利用废物制备生物质能源是环境保护和能源开发领域的有益尝试。利用厌氧发酵液中挥发性脂肪酸（VFAs）培养微藻能够实现高效、低成本的产油，对解决制约微藻生物柴油规模化生产的高成本问题具有重要的意义。废物能否被有效利用是决定废物处理后是否产生二次污染以及藻类高效产油的关键问题。本项目拟从微藻利用废物产油的源头入手，筛选耐受异养环境的高产油脂能源微藻，研究环境因子对其利用VFAs产油特性和底物利用的影响，探索优势能源微藻高效脂类积累，同时实现高效利用VFAs的最佳环境条件；揭示优势能源微藻生长速率与底物利用效果和碳流分配之间的关系，阐明异养型优势能源微藻利用VFAs高效积累油脂的代谢调控机制，为实现废物的深度利用和利用微藻高效产能提供科学技术理论支撑。项目的研究成功将实现藻类处理废物、废物生产能源的有机统一，实现净化环境和降低成本产能源的双赢，具有重要的理论意义。

本项目探究异养型优势能源微藻利用厌氧发酵液中挥发性脂肪酸（VFAs）制备生物质能源，研究目标基本完成。结果如下：首先驯化选育出耐受异养环境的藻株2株，选取前期筛选获得的优势能源微藻蛋白核小球藻和四尾栅藻为研究对象，以乙酸和木糖为有机碳源，考察在混养和异养下的生长和产油特性，获得最佳环境条件，明确了其利用发酵液中的有机物进行生长和产油的可行性。其次，选择乙酸、丙酸、丁酸作为有机碳源，获得了两株优势能源微藻异养和混养条件下的最优挥发酸比例，考察了其在最优挥发酸比例下生长、产油、挥发酸和氮磷的去除情况。最后通过考察最优环境条件下异养型能源微藻生长速率、产油效率和底物利用效率之间的关系，揭示了能源微藻利用VFAs高效产油的碳氮调控机理。结果表明蛋白核小球藻对乙酸的吸收速率与乙酸投加浓度呈负相关，当异养条件下乙酸浓度为6g/L时，底物转化因子即每克乙酸产生物量值、每克乙酸产油脂量值、每克乙酸对氮的吸收系数和每克乙酸对磷的吸收系数达到最大值。两株异养型能源微藻均可高效利用挥发酸进行油脂积累，蛋白核小球藻和四尾栅藻分别在最优挥发酸比例（乙酸：丙酸：丁酸）4:5:1和6:1:3下对乙酸的利用率最高，其次是丙酸和丁酸。异养下挥发酸中乙酸利用率越高越利于细胞生长和油脂积累，这可能是由于在乙酸、丙酸和丁酸被藻细胞吸收转化为乙酰辅酶A的过程中，乙酸的转化所需能量少且代谢路径短的原因。由于乙酰辅酶A是细胞代谢的重要分子和中间产物，也是合成脂肪酸等能量物质的前体。乙酸的吸收不仅提高了微藻生物量，还促进了油脂的积累。以上研究成果为微藻高效产能与废物深度利用奠定了理论基础，有望实现能源微藻的低成本和环境友好培养的有机统一。