Zha Wenjuan, Rubin-Pitel Sheryl B, Shao Zengyi, Zhao Huimin
Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Metab Eng. 2009 May;11(3):192-8. doi: 10.1016/j.ymben.2009.01.005. Epub 2009 Feb 5.
Escherichia coli only maintains a small amount of cellular malonyl-CoA, impeding its utility for overproducing natural products such as polyketides and flavonoids. Here, we report the use of various metabolic engineering strategies to redirect the carbon flux inside E. coli to pathways responsible for the generation of malonyl-CoA. Overexpression of acetyl-CoA carboxylase (Acc) resulted in 3-fold increase in cellular malonyl-CoA concentration. More importantly, overexpression of Acc showed a synergistic effect with increased acetyl-CoA availability, which was achieved by deletion of competing pathways leading to the byproducts acetate and ethanol as well as overexpression of an acetate assimilation enzyme. These engineering efforts led to the creation of an E. coli strain with 15-fold elevated cellular malonyl-CoA level. To demonstrate its utility, this engineered E. coli strain was used to produce an important polyketide, phloroglucinol, and showed near 4-fold higher titer compared with wild-type E. coli, despite the toxicity of phloroglucinol to cell growth. This engineered E. coli strain with elevated cellular malonyl-CoA level should be highly useful for improved production of important natural products where the cellular malonyl-CoA level is rate-limiting.
大肠杆菌仅维持少量的细胞丙二酰辅酶A，这阻碍了其用于过量生产聚酮化合物和类黄酮等天然产物。在此，我们报告了使用各种代谢工程策略将大肠杆菌内的碳通量重定向至负责丙二酰辅酶A生成的途径。乙酰辅酶A羧化酶（Acc）的过表达导致细胞丙二酰辅酶A浓度增加了3倍。更重要的是，Acc的过表达与增加的乙酰辅酶A可用性显示出协同效应，这是通过删除导致副产物乙酸和乙醇的竞争途径以及过表达一种乙酸同化酶来实现的。这些工程努力导致创建了一种细胞丙二酰辅酶A水平提高了15倍的大肠杆菌菌株。为了证明其效用，这种工程化的大肠杆菌菌株被用于生产一种重要的聚酮化合物间苯三酚，并且尽管间苯三酚对细胞生长有毒性，但与野生型大肠杆菌相比，其产量仍高出近4倍。这种细胞丙二酰辅酶A水平升高的工程化大肠杆菌菌株对于改善细胞丙二酰辅酶A水平为限速因素的重要天然产物的生产应该非常有用。
