Department of Chemical Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada.
Biotechnol Biofuels. 2013 Sep 28;6(1):139. doi: 10.1186/1754-6834-6-139.
While most resources in biofuels were directed towards implementing bioethanol programs, 1-propanol has recently received attention as a promising alternative biofuel. Nevertheless, no microorganism has been identified as a natural 1-propanol producer. In this study, we manipulated a novel metabolic pathway for the synthesis of 1-propanol in the genetically tractable bacterium Escherichia coli.
E. coli strains capable of producing heterologous 1-propanol were engineered by extending the dissimilation of succinate via propionyl-CoA. This was accomplished by expressing a selection of key genes, i.e. (1) three native genes in the sleeping beauty mutase (Sbm) operon, i.e. sbm-ygfD-ygfG from E. coli, (2) the genes encoding bifunctional aldehyde/alcohol dehydrogenases (ADHs) from several microbial sources, and (3) the sucCD gene encoding succinyl-CoA synthetase from E. coli. Using the developed whole-cell biocatalyst under anaerobic conditions, production titers up to 150 mg/L of 1-propanol were obtained. In addition, several genetic and chemical effects on the production of 1-propanol were investigated, indicating that certain host-gene deletions could abolish 1-propanol production as well as that the expression of a putative protein kinase (encoded by ygfD/argK) was crucial for 1-propanol biosynthesis.
The study has provided a novel route for 1-propanol production in E. coli, which is subjected to further improvement by identifying limiting conversion steps, shifting major carbon flux to the productive pathway, and optimizing gene expression and culture conditions.
虽然大多数生物燃料资源都致力于实施生物乙醇计划，但 1-丙醇最近作为一种很有前途的替代生物燃料受到了关注。然而，尚未发现能够自然生产 1-丙醇的微生物。在这项研究中，我们在遗传上易于操作的大肠杆菌中操纵了一条用于合成 1-丙醇的新代谢途径。
通过扩展琥珀酸的异化作用来合成丙酰辅酶 A，构建了能够生产异源 1-丙醇的大肠杆菌菌株。这是通过表达一系列关键基因来实现的，即（1）大肠杆菌中睡眠美人突变酶（Sbm）操纵子中的三个天然基因，即 sbm-ygfD-ygfG，（2）来自多种微生物来源的双功能醛/醇脱氢酶（ADHs）基因，和（3）编码来自大肠杆菌的琥珀酰辅酶 A 合成酶的 sucCD 基因。在厌氧条件下使用开发的全细胞生物催化剂，可获得高达 150mg/L 的 1-丙醇生产滴度。此外，还研究了对 1-丙醇生产的几种遗传和化学影响，表明某些宿主基因缺失可能会阻止 1-丙醇的产生，并且假定蛋白激酶（由 ygfD/argK 编码）的表达对于 1-丙醇生物合成至关重要。
该研究为大肠杆菌中 1-丙醇的生产提供了一条新途径，通过鉴定限制转化步骤、将主要碳通量转移到生产途径、优化基因表达和培养条件，该途径有待进一步改进。
