Engineering central pathways for industrial-level (3R)-acetoin biosynthesis in Corynebacterium glutamicum
Engineering central pathways for industrial-level (3R)-acetoin biosynthesis in Corynebacterium glutamicum
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DOI：
10.1186/s12934-020-01363-8
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发表时间：
2020-05-12
影响因子：
6.4
通讯作者：
Chen, Tao
中科院分区：
文献类型：
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作者：
Lu, Lingxue;Mao, Yufeng;Chen, Tao
背景乙偶姻，特别是光学纯的（3S）-或（3R）-对映体，是一种高附加值的生物基平台化学品和重要的潜在药物中间体。在过去的几十年里，人们一直致力于通过绿色生物技术生产乙偶姻。然而，用于生产光学纯乙偶姻对映体的有效和经济的方法很少报道。以前，我们系统地改造了GRAS微生物谷氨酸棒杆菌以从葡萄糖有效地生产（3R）-乙偶姻。尽管如此，其产量和平均生产率仍然不能令人满意的工业生物过程。结果在本研究中，在乙偶姻生产者CGR 6的细胞碳通量进一步转向乙偶姻合成使用几种代谢工程策略，包括阻断回补途径，衰减TCA循环的关键基因和整合额外拷贝的alsSD操纵子到基因组中。其中，柠檬酸合成酶的衰减和磷酸烯醇式丙酮酸羧化酶的失活的组合显示出显着的协同效应，对乙偶姻生产。工程菌CGS 11在5L发酵罐中以1.86g/L/h的速率发酵，乙偶姻效价为102.45g/L，葡萄糖产量为0.419g/g。所得（3R）-乙偶姻的光学纯度超过95%。结论这是一种简单、绿色、不需要昂贵的添加剂或底物的高对映体富集的（3R）-乙偶姻的最高滴度，以及具有竞争力的产物产率和生产率。因此，该方法为在不久的将来通过微生物发酵实现（3R）-乙偶姻的简单、有效、经济和环境友好的生产提供了可能性。
Background Acetoin, especially the optically pure (3S)- or (3R)-enantiomer, is a high-value-added bio-based platform chemical and important potential pharmaceutical intermediate. Over the past decades, intense efforts have been devoted to the production of acetoin through green biotechniques. However, efficient and economical methods for the production of optically pure acetoin enantiomers are rarely reported. Previously, we systematically engineered the GRAS microorganism Corynebacterium glutamicum to efficiently produce (3R)-acetoin from glucose. Nevertheless, its yield and average productivity were still unsatisfactory for industrial bioprocesses. Results In this study, cellular carbon fluxes in the acetoin producer CGR6 were further redirected toward acetoin synthesis using several metabolic engineering strategies, including blocking anaplerotic pathways, attenuating key genes of the TCA cycle and integrating additional copies of the alsSD operon into the genome. Among them, the combination of attenuation of citrate synthase and inactivation of phosphoenolpyruvate carboxylase showed a significant synergistic effect on acetoin production. Finally, the optimal engineered strain CGS11 produced a titer of 102.45 g/L acetoin with a yield of 0.419 g/g glucose at a rate of 1.86 g/L/h in a 5 L fermenter. The optical purity of the resulting (3R)-acetoin surpassed 95%. Conclusion To the best of our knowledge, this is the highest titer of highly enantiomerically enriched (3R)-acetoin, together with a competitive product yield and productivity, achieved in a simple, green processes without expensive additives or substrates. This process therefore opens the possibility to achieve easy, efficient, economical and environmentally-friendly production of (3R)-acetoin via microbial fermentation in the near future.