Cyanobacteria are emerging as hosts for photoautotrophic production of chemicals. Recent studies have attempted to stretch the limits of photosynthetic production, typically focusing on one product at a time, possibly to minimise the additional burden of product separation. Here, we explore the simultaneous production of two products that can be easily separated: ethylene, a gaseous product, and succinate, an organic acid that accumulates in the culture medium. This was achieved by expressing a single copy of the ethylene forming enzyme (efe) under the control of P_cpcB, the inducer-free super-strong promoter of phycocyanin β subunit. We chose the recently reported, fast-growing and robust cyanobacterium, Synechococcus elongatus PCC 11801, as the host strain. A stable recombinant strain was constructed using CRISPR-Cpf1 in a first report of markerless genome editing of this cyanobacterium. Under photoautotrophic conditions, the recombinant strain shows specific productivities of 338.26 and 1044.18 μmole/g dry cell weight/h for ethylene and succinate, respectively. These results compare favourably with the reported productivities for individual products in cyanobacteria that are highly engineered. Metabolome profiling and ¹³C labelling studies indicate carbon flux redistribution and suggest avenues for further improvement. Our results show that S. elongatus PCC 11801 is a promising candidate for metabolic engineering.

中文翻译：

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在快速生长的蓝藻中，琥珀酸和乙烯的光合作用共同产生，即细长突触球菌PCC 11801。

蓝细菌正在成为光合自养化学物质的宿主。最近的研究试图扩大光合作用的生产极限，通常一次只关注一种产品，这可能会最大程度地减少产品分离的额外负担。在这里，我们探讨了可以轻松分离的两种产品的同时生产：乙烯（一种气态产物）和琥珀酸酯（一种在培养基中积累的有机酸）。这是通过在P _cpcB（藻蓝蛋白β亚基的无诱导剂超强启动子）的控制下表达单拷贝的乙烯形成酶（efe）来实现的。我们选择了最近报道的，快速增长且健壮的蓝藻，即Synchococcus elongatus。PCC 11801，作为宿主菌株。在此蓝细菌的无标记基因组编辑的第一篇报道中，使用CRISPR-Cpf1构建了稳定的重组菌株。在光合自养条件下，重组菌株对乙烯和琥珀酸的比生产率分别为338.26和1044.18μmole/ g干细胞重量/ h。这些结果与蓝藻中高度工程化的单个产品的报道生产率相比具有优势。代谢物谱分析和¹³ C标记研究表明碳通量重新分布，并提出了进一步改善的途径。我们的结果表明，S。elongatus PCC 11801是代谢工程的有希望的候选者。