Carmona Susy Beatriz, Moreno Fabián, Bolívar Francisco, Gosset Guillermo, Escalante Adelfo
Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico.
J Mol Microbiol Biotechnol. 2015;25(2-3):195-208. doi: 10.1159/000380854. Epub 2015 Jul 9.
Laboratory and industrial cultures of Escherichia coli employ media containing glucose which is mainly transported and phosphorylated by the phosphotransferase system (PTS). In these strains, 50% of the phosphoenolpyruvate (PEP), which results from the catabolism of transported glucose, is used as a phosphate donor for its phosphorylation and translocation by the PTS. This characteristic of the PTS limits the production of industrial biocommodities that have PEP as a precursor. Furthermore, when E. coli is exposed to carbohydrate mixtures, the PTS prevents expression of catabolic and non-PTS transport genes by carbon catabolite repression and inducer exclusion. In this contribution, we discuss the main strategies developed to overcome these potentially limiting effects in production strains. These strategies include adaptive laboratory evolution selection of PTS(-) Glc(+) mutants, followed by the generation of strains that recover their ability to grow with glucose as a carbon source while allowing the simultaneous consumption of more than one carbon source. We discuss the benefits of using alternative glucose transport systems and describe the application of these strategies to E. coli strains with specific genetic modifications in target pathways. These efforts have resulted in significant improvements in the production of diverse biocommodities, including aromatic metabolites, biofuels and organic acids.
大肠杆菌的实验室培养和工业培养使用含有葡萄糖的培养基，葡萄糖主要通过磷酸转移酶系统（PTS）进行转运和磷酸化。在这些菌株中，由转运的葡萄糖分解代谢产生的磷酸烯醇丙酮酸（PEP）有50%被用作磷酸盐供体，用于其通过PTS进行磷酸化和转运。PTS的这一特性限制了以PEP为前体的工业生物商品的生产。此外，当大肠杆菌暴露于碳水化合物混合物中时，PTS会通过碳分解代谢物阻遏和诱导物排除来阻止分解代谢和非PTS转运基因的表达。在本论文中，我们讨论了为克服生产菌株中这些潜在限制作用而开发的主要策略。这些策略包括对PTS(-) Glc(+)突变体进行适应性实验室进化选择，随后构建能够恢复以葡萄糖作为碳源生长的能力同时允许同时消耗多种碳源的菌株。我们讨论了使用替代葡萄糖转运系统的益处，并描述了这些策略在目标途径中具有特定基因修饰的大肠杆菌菌株中的应用。这些努力已使包括芳香族代谢物、生物燃料和有机酸在内的多种生物商品的产量得到显著提高。
