Squalene synthase (SQS) catalyzes the conversion of two farnesyl pyrophosphates to squalene, an important intermediate in between isoprene and valuable triterpenoids. In this study, we have constructed a novel biosynthesis pathway for squalene in Bacillus subtilis and performed metabolic engineering aiming at facilitating further exploitation and production of squalene-derived triterpenoids. Therefore, systematic studies and analysis were performed including selection of multiple SQS candidates from various organisms, comparison of expression vectors, optimization of cultivation temperatures, and examination of rate-limiting factors within the synthetic pathway. We were, for the first time, able to obtain squalene synthesis in B. subtilis. Furthermore, we achieved a 29-fold increase of squalene yield (0.26-7.5 mg/L) by expressing SQS from Bacillus megaterium and eliminating bottlenecks within the upstream methylerythritol-phosphate pathway. Moreover, our findings showed that also ispA could positively affect the production of squalene.

中文翻译：

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通过角鲨烯合酶筛选和代谢工程在枯草芽孢杆菌中产生角鲨烯。

角鲨烯合酶（SQS）催化将两种法呢基焦磷酸酯转化为角鲨烯，这是异戊二烯和有价值的三萜之间的重要中间体。在这项研究中，我们为枯草芽孢杆菌中的角鲨烯构建了一条新的生物合成途径，并进行了代谢工程，旨在促进角鲨烯衍生的三萜类化合物的进一步开发和生产。因此，进行了系统的研究和分析，包括从各种生物中选择多个SQS候选物，比较表达载体，优化培养温度以及检查合成途径中的限速因子。我们首次能够在枯草芽孢杆菌中获得角鲨烯合成。此外，我们将角鲨烯的收率提高了29倍（0.26-7。5 mg / L），通过表达巨大芽孢杆菌的SQS并消除上游甲基赤藓糖醇-磷酸途径中的瓶颈。此外，我们的发现表明，ispA也可以对角鲨烯的产生产生积极影响。