产角鲨烯细胞工厂的构建及关键基因的筛选、克隆与表达

Construction of squalene producing cell factories and screening, cloning and expression of key genes

摘要:

角鲨烯因具有很强的抗氧化、抗菌和抗肿瘤活性，被普遍应用于医药、保健品和化妆品等领域。文中在实验室构建的高效合成萜类化合物底盘菌株工作的基础上，以角鲨烯为目标产物，通过过表达法尼基焦磷酸合酶基因ispA得到高效合成三萜化合物的底盘菌株；然后对原核生物来源的角鲨烯合酶进行系统发育分析、筛选、克隆和表达，得到两株高效合成角鲨烯的大肠杆菌Escherichia coli工程菌株。其中，导入来源于嗜热蓝细菌Thermosynechococcus elongatus和深蓝聚球蓝细菌Synechococcus lividus的角鲨烯合酶的工程菌株，角鲨烯产量分别达到 (16.5±1.4) mg/g (细胞干重含量，后同) 和 (12.0±1.9) mg/g，发酵液浓度达到 (167.1±14.3) mg/L和(121.8±19.5) mg/L。相比于当前普遍使用的人源角鲨烯合酶及初代菌株，来源于T. elongatus和S. lividus的角鲨烯合酶分别使角鲨烯产量大幅提升了3.3倍和2.4倍，为原核细胞异源合成角鲨烯打下坚实的基础。

Abstract:

Squalene is widely used in pharmaceutical, nutraceutical, cosmetics and other fields because of its strong antioxidative, antibacterial and anti-tumor activities. In order to produce squalene, a gene ispA encoding farnesyl pyrophosphate synthase was overexpressed in a previously engineered Escherichia coli strain capable of efficiently producing terpenoids, resulting in a chassis strain that efficiently synthesizes triterpenoids. Through phylogenetic analysis, screening, cloning and expression of squalene synthase derived from different prokaryotes, engineered E. coli strains capable of efficiently producing squalene were obtained. Among them, squalene produced by strains harboring squalene synthase derived from Thermosynechococcus elongatus and Synechococcus lividus reached (16.5±1.4) mg/g DCW ((167.1±14.3) mg/L broth) and (12.0±1.9) mg/g DCW ((121.8±19.5) mg/L broth), respectively. Compared with the first-generation strains harboring the human-derived squalene synthase, the squalene synthase derived from T. elongatus and S. lividus remarkably increased the squalene production by 3.3 times and 2.4 times, respectively, making progress toward the cost-effective heterologous production of squalene.