裂殖壶菌利用聚酮合成酶（Polyketide synthase, PKS）途径合成二十碳五烯酸代谢机制

Omega3-long-chain polyunsaturated fatty acids are important components of the human diet supplements because of their contribution to several aspects of health, including the development of the infant brain, the function of the eye, the synthesis of hormones and signaling molecules, and the prevention of cardiovascular diseases. Microbial docosahexaenoic acid (DHA) has been widely industrialized. However, EPA from microorganism is still a long way to commercial production. In this research, the gene clusters of polyketide synthase pathway (PKS) from both Schizochytrium ATCC1381 and Shewanella MR-1 were analyzed and then compared to get the key differential genes regarding PUFAs production. The key genes encoding EPA/DHA synthesis were then determined in Schizochytrium sp. Furthermore, an engineered Schizochytrium was constructed to overproduce EPA. The metabolic and regulation mechanisms of the PKS pathway for PUFAs synthesis were finally revealled including the role of ketosynthase-chain length factor (KS-CLF) during EPA synthesis in Schizochytrium.

Omega3多不饱和脂肪酸（Polyunsaturated fatty acids, PUFAs）在生物细胞中发挥重要作用。目前二十二碳六烯酸（Docohexanoic acid, DHA）已实现大规模微生物生产和市场化，然而微生物来源二十碳五烯酸（Eicosapentaenoic acid, EPA）短缺仍是该产品商业化限制因素。本项目通过解析裂殖壶菌Schizochytrium ATCC1381和希瓦氏菌Shewanella MR-1聚酮合成酶（Polyketide synthase，PKS）基因簇结构，比对分析定位关键差异基因，确定Schizochytrium ATCC1381利用PKS途径合成EPA/DHA的关键控制基因位点，进而定向重组构建EPA合成工程菌株，阐明裂殖壶菌PKS途径合成多不饱和脂肪酸的代谢与调控机制，揭示链长基因KS-CLF在裂殖壶菌合成EPA过程中的功能。

Omega 3多不饱和脂肪酸（Polyunsaturated fatty acids, PUFAs）不仅在生物细胞中发挥重要生理功能，也是人类膳食补充剂的重要组成部分。目前二十二碳六烯酸（Docohexanoic acid, DHA）已实现大规模微生物生产和市场化，然而微生物来源二十碳五烯酸（Eicosapentaenoic acid, EPA）仍因产量低而使其商业化受限。本项目通过获取裂殖壶菌聚酮合成酶（Polyketide synthase, PKS）途径基因簇关键生物学信息，经比对分析定位了该菌株PUFAs合成种类的控制基因。在此基础上，采用敲除/定点突变/过表达等代谢工程手段深入解析了PKS基因簇结构域组成及其功能，结合代谢组和转录组等组学技术，揭示了裂殖壶菌利用PKS/FAS途径合成EPA/DHA代谢机制，为阐明裂殖壶菌PUFAs合成代谢网络与调控模型提供有力的技术支撑。此外，利用基因工程改造和定向驯化等手段，最终获得了EPA/DHA裂殖壶菌工程菌株，确定其基础培养基配方并对其发酵过程进行优化控制，建立了EPA/DHA发酵合成工艺，该工艺的建立对于实现微生物来源的EPA工业化生产具有重要意义。