Liu Min, Ding Yamei, Chen Hailin, Zhao Zhe, Liu Huizhou, Xian Mo, Zhao Guang
CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China.
Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China.
BMC Microbiol. 2017 Jan 7;17(1):10. doi: 10.1186/s12866-016-0913-2.
Acetyl-CoA-derived chemicals are suitable for multiple applications in many industries. The bio-production of these chemicals has become imperative owing to the economic and environmental problems. However, acetate overflow is the major drawback for acetyl-CoA-derived chemicals production. Approaches for overcoming acetate overflow may be beneficial for the production of acetyl-CoA-derived chemicals.
In this study, a transcriptional regulator iclR was knocked out in E.coli BL21(DE3) to overcome acetate overflow and improve the chemicals production. Two important acetyl-CoA-derived chemicals, phloroglucinol (PG) and 3-hydroxypropionate (3HP) were used to evaluate it. It is revealed that knockout of iclR significantly increased expressions of aceBAK operon. The cell yields and glucose utilization efficiencies were higher than those of control strains. The acetate concentrations were decreased by more than 50% and the productions of PG and 3HP were increased more than twice in iclR mutants. The effects of iclR knockout on cell physiology, cell metabolism and production of acetyl-CoA-derived chemicals were similar to those of arcA knockout in our previous study. However, the arcA-iclR double mutants couldn't gain higher productions of PG and 3HP. The mechanisms are unclear and needed to be resolved in future.
Knockout of iclR significantly increased gene expression of aceBAK operon and concomitantly activated glyoxylate pathway. This genetic modification may be a good way to overcome acetate overflow, and improve the production of a wide range of acetyl-CoA-derived chemicals.
乙酰辅酶A衍生的化学品适用于许多行业的多种应用。由于经济和环境问题，这些化学品的生物生产变得势在必行。然而，乙酸溢流是乙酰辅酶A衍生化学品生产的主要缺点。克服乙酸溢流的方法可能有利于乙酰辅酶A衍生化学品的生产。
在本研究中，在大肠杆菌BL21(DE3)中敲除转录调节因子iclR以克服乙酸溢流并提高化学品产量。使用两种重要的乙酰辅酶A衍生化学品间苯三酚（PG）和3-羟基丙酸（3HP）对其进行评估。结果表明，敲除iclR显著增加了aceBAK操纵子的表达。细胞产量和葡萄糖利用效率高于对照菌株。在iclR突变体中，乙酸浓度降低了50%以上，PG和3HP的产量增加了两倍多。在我们之前的研究中，敲除iclR对细胞生理、细胞代谢和乙酰辅酶A衍生化学品生产的影响与敲除arcA相似。然而，arcA-iclR双突变体无法获得更高的PG和3HP产量。其机制尚不清楚，有待未来解决。
敲除iclR显著增加了aceBAK操纵子的基因表达，并同时激活了乙醛酸途径。这种基因改造可能是克服乙酸溢流、提高多种乙酰辅酶A衍生化学品产量的好方法。
