In view of the environmental problems associated with climate change and greenhouse gas emissions, the potential of carbon sequestration has emerged as a research hotspot. Cyanobacteria can use solar energy and carbon dioxide to produce organic molecules bypassing the need for carbohydrate feedstock. This valuable trait has spearheaded its use in the field of bioproduction and ultimately metabolic engineering. As a natural phenolic compound, p-Coumaric acid is widely present in plants. Like other secondary metabolites, they are mainly produced to protect the plants against stress. p-Coumaric acid has many antioxidant and anti-inflammatory properties which are of importance to the pharmaceutical, food, cosmetic, and agricultural industries as precursors of active ingredients.

In this study, we report the heterologous expression of the phenylalanine ammonia-lyase (PAL) and the cinnamic acid 4-hydroxylase (C4H) exogenous genes under the Pcpc560 promoter in the cyanobacteria Synechocystis sp. PCC6803. After 7 days of photoautotrophic growth, 0.8 mM of p-Coumaric acid was produced. To further increase production titer, we knocked out the Synechocystis sp. PCC6803 gene encoding the arogenate dehydrogenase which led to the production of 1.2 mM p-Coumaric acid after 7 days of photoautotrophic growth. Our work provides more insight into the double-step phenylpropanoid biosynthesis pathway contributing to extend the knowledge of the cyanobacteria's ability to produce plant secondary metabolites directly from carbon dioxide.

鉴于与气候变化和温室气体排放相关的环境问题，碳固存的潜力已经成为研究热点。蓝细菌可以利用太阳能和二氧化碳来生产有机分子，从而无需碳水化合物原料。这种宝贵的特性已在生物生产和最终代谢工程领域发挥了带头作用。作为天然的酚类化合物，对香豆酸广泛存在于植物中。像其他次生代谢产物一样，它们主要是为了保护植物免受胁迫而产生的。对香豆酸具有许多抗氧化剂和抗发炎特性，作为活性成分的前体对于制药，食品，化妆品和农业行业而言非常重要。

在这项研究中，我们报告了蓝藻Synechocystis sp。中Pcpc560启动子下苯丙氨酸解氨酶（PAL）和肉桂酸4-羟化酶（C4H）外源基因的异源表达。PCC6803。光合自养生长7天后，产生0.8mM的对-香豆酸。为了进一步提高生产效价，我们敲除了Synechocystis sp.。PCC6803基因编码导致其产生1.2 mM p的Arnateate脱氢酶-自养7天后，香豆酸。我们的工作为双步苯丙类生物合成途径提供了更多的见识，有助于扩展对蓝细菌直接从二氧化碳生产植物次级代谢产物能力的认识。