Abstract:

Sesquiterpenoids α-neoclovene and β-caryophyllene are major components in volatile oils from Panax ginseng, which have been demonstrated to play important roles in antibacteria, antitumor and cardiovascular protection. Moreover, they have attracted attentions for potential use as biofuels with high-energy-density. However, the industrial production of α-neoclovene and β-caryophyllene as well as other sesquiterpenoids are mainly relied on extraction from plant materials, which is too costly for applications at a large scale. Currently, this challenge could be addressed by advances in synthetic biology for natural product biosynthesis. Through heterologously assembling and integrating of their biosynthetic pathways into microbial chassis cells, targeted natural compounds from plants could be produced by microbial fermentation in a sustainable, low-cost and large-scale way. In this study, by comparing the production potential of sesquiterpenes between different Saccharomyces cerevisiae strainsand followed by enhancing the endogenous mevalonate pathway, a yeast sesquiterpene chassis strain (SQTBY03) with an increase of 458 times in farnesyl pyrophosphate production was constructed. Then by inserting the codon-optimized sesquiterpene synthase gene ec38-cs from the endophytic fungi Hypoxylon sp. EC38 and the codon-optimized caryophyllene synthase gene QHS1 from Artemisia annua into SQTBY03, respectively, we built yeast cell factories NCVBY01 and CPLBY01 for de novo production of α-neoclovene and β-caryophyllene at their titers of 25.8 mg/L and 250.4 mg/L, respectively, in shake flasks. Furthermore, fed-batch fermentation using NCVBY01 and CPLBY01 resulted in the de novo production of 487.1 mg/L α-neoclovene and 2949.1 mg/L β-caryophyllene from glucose. It is also possible to further chemically catalyze β-caryophyllene to produce α-neoclovene. Our work provides strategies for the sustainable production of α-neoclovene and β-caryophyllene from glucose through microbial fermentation, which would benefit their applications as medicine and other functional products. In addition, our yeast chassis for the sesquiterpene production could offer a platform for the sustainable production of other valuable sesquiterpenoids via synthetic biology approach.

Key words: sesquiterpenoids, Saccharomyces cerevisiae, cell factory, α-neoclovene, β-caryophyllene

摘要：

倍半萜类化合物（sesquiterpenoids）α-新丁香三环烯（α-neoclovene）和β-石竹烯（β-caryophyllene）都是人参挥发油中的主要组成成分，不仅具有重要的药用开发价值，而且在高能量密度生物能源的开发中也受到关注。然而，它们在人参和其他植物中含量均十分稀少且难以分离纯化，其开发与应用研究严重滞后。本研究利用天然产物合成生物学的方法，以BY4742为出发菌株构建了高产倍半萜类化合物前体FPP的通用底盘菌株SQTBY03。在此底盘菌株中异源表达了密码子优化的植物内生真菌Hypoxylon sp. EC38来源的多产物倍半萜合酶元件基因ec38-cs和黄花蒿（Artemisia annua）来源的倍半萜合酶元件基因QHS1，分别构建了合成α-新丁香三环烯和β-石竹烯的两个倍半萜细胞工厂NCVBY01和CPLBY01。细胞工厂NCVBY01的主要倍半萜产物为α-新丁香三环烯（>39%），细胞工厂CPLBY01的主要产物为β-石竹烯（>96%）。它们的摇瓶发酵产量分别达到25.8 mg/L和250.4 mg/L。通过在1.3 L发酵罐中进行批次补料发酵，细胞工厂NCVBY01合成α-新丁香三环烯的产量达到了487.1 mg/L，为目前首次在微生物细胞工厂中合成α-新丁香三环烯；CPLBY01合成β-石竹烯的产量达到2949.1 mg/L，为目前报道的最高水平。上述研究成果为α-新丁香三环烯和β-石竹烯的规模化制备提供新的途径。

关键词: 倍半萜类, 酿酒酵母, 细胞工厂, α-新丁香三环烯, β-石竹烯