Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin University, Tianjin, 300072, China.
Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin University, Tianjin, 300072, China.
Metab Eng. 2021 Jul;66:51-59. doi: 10.1016/j.ymben.2021.03.019. Epub 2021 Apr 19.
Microbial production of monoterpenes has attracted increasing attention in recent years. Up to date, there are only few reports on the biosynthesis of the monoterpene alcohol citronellol that is widely used as fragrant and pharmaceutical intermediates. Here, we engineered Saccharomyces cerevisiae by employing a "push-pull-restrain" strategy to improve citronellol production based on the reduction of geraniol. Starting from a engineered geraniol-producing strain, different reductases were investigated and the best performing iridoid synthase from Catharanthus roseus (CrIS) resulted in 285.89 mg/L enantiomerically pure S-citronellol in shake flasks. Geranyl diphosphate (GPP), the most important precursor for monoterpenes, was enhanced by replacing the wild farnesyl diphosphate synthase (Erg20) with the mutant Erg20, increasing the citronellol titer to 406.01 mg/L without negative influence on cell growth. Moreover, we employed synthetic protein scaffolds and protein fusion to colocalize four sequential enzymes to achieve better substrate channeling along with the deletion of an intermediate degradation pathway gene ATF1, which elevated the citronellol titer to 972.02 mg/L with the proportion of 97.8% of total monoterpenes in YPD medium. Finally, the engineered strain with complemented auxotrophic markers produced 8.30 g/L of citronellol by fed-batch fermentation, which was the highest citronellol titer reported to date. The multi-level engineering strategies developed here demonstrate the potential of monoterpenes overproduction in yeast, which can serve as a generally applicable platform for overproduction of other monoterpenes.
近年来,微生物生产单萜引起了越来越多的关注。迄今为止,关于广泛用作香料和药物中间体的单萜醇橙花醇生物合成的报道只有少数。在这里,我们采用“推-拉-抑制”策略,通过减少香叶醇来设计酿酒酵母,以提高橙花醇的产量。从一个工程化的香叶醇生产菌株开始,研究了不同的还原酶,来自长春花(Catharanthus roseus)的表现最好的裂环烯醚萜合酶(CrIS)导致摇瓶中产生 285.89 mg/L 对映体纯 S-香茅醇。香叶基二磷酸(GPP)是单萜的最重要前体,通过用突变的法尼基二磷酸合酶(Erg20)取代野生型法尼基二磷酸合酶(Erg20)来增强 GPP,使橙花醇的产量提高到 406.01 mg/L,而对细胞生长没有负面影响。此外,我们采用合成蛋白支架和蛋白融合将四个连续的酶共定位,以实现更好的底物通道化,并删除中间降解途径基因 ATF1,这将橙花醇的产量提高到 972.02 mg/L,总单萜的比例为 97.8%在 YPD 培养基中。最后,带有补充营养缺陷型标记的工程菌株通过分批补料发酵生产了 8.30 g/L 的香茅醇,这是迄今为止报道的最高香茅醇产量。这里开发的多层次工程策略展示了酵母中单萜过量生产的潜力,可为其他单萜的过量生产提供一个通用的平台。