Ethylene is a small hydrocarbon gas widely used in the chemical industry. Annual worldwide production currently exceeds 150 million tons, producing considerable amounts of CO₂ contributing to climate change. The need for a sustainable alternative is therefore imperative. Ethylene is natively produced by several different microorganisms, including Pseudomonas syringae pv. phaseolicola via a process catalyzed by the ethylene-forming enzyme (EFE), subsequent heterologous expression of EFE has led to ethylene production in non-native bacterial hosts including Escherichia coli and cyanobacteria. However, solubility of EFE and substrate availability remain rate-limiting steps in biological ethylene production. We employed a combination of genome-scale metabolic modelling, continuous fermentation, and protein evolution to enable the accelerated development of a high efficiency ethylene producing E. coli strain, yielding a 49-fold increase in production, the most significant improvement reported to date. Furthermore, we have clearly demonstrated that this increased yield resulted from metabolic adaptations that were uniquely linked to EFE (wild type versus mutant). Our findings provide a novel solution to deregulate metabolic bottlenecks in key pathways, which can be readily applied to address other engineering challenges.

乙烯是化学工业中广泛使用的一种小型碳氢化合物气体。目前全球年产量超过 1.5 亿吨，产生大量导致气候变化的 CO ₂。因此，迫切需要一种可持续的替代方案。乙烯是由几种不同的微生物天然产生的，包括丁香假单胞菌pv。菜豆通过由乙烯形成酶（EFE）催化的方法，EFE随后异源表达导致了乙烯生产在非天然细菌宿主包括大肠杆菌和蓝藻。然而，EFE 的溶解度和底物可用性仍然是生物乙烯生产中的限速步骤。我们结合了基因组规模的代谢建模、连续发酵和蛋白质进化，以加速开发高效产乙烯的大肠杆菌菌株，使产量增加 49 倍，这是迄今为止报道的最显着的改进。此外，我们已经清楚地证明，这种增加的产量是由与 EFE（野生型与突变型）独特相关的代谢适应引起的。我们的发现提供了一种新的解决方案来解除关键途径中的代谢瓶颈，可以很容易地应用于解决其他工程挑战。