大肠杆菌cdd和thrA基因的敲除及其对胞苷积累量的影响

Effect of Gene knockout of cdd and thrA on Cytidine Production in E. coli

以大肠杆菌AU39作为出发菌株,通过基因工程手段对其进行改造,旨在提高胞苷产量。首先,通过Red重组系统敲除了大肠杆菌AU39基因组上的胞苷脱氨酶基因cdd,阻断了胞苷的分解代谢;敲除了E.coli AU39(Δcdd)基因组上的高丝氨酸脱氢酶基因thrA,阻断天冬氨酸向高丝氨酸的代谢途径。然后,分别对不同基因缺失菌株进行培养发酵,与出发菌株E.coli AU39相比,两株突变株都有不同程度的胞苷积累,E.coli AU39(Δcdd)与E.coli AU39(ΔcddΔthrA)的胞苷产量提高了1.25倍与1.6倍,而尿苷产量均相对有所降低。

In order to develop a host strain to produce cytidine, a synthetic pathway has been constructed for the production of cytidine from glucose in Escherichia coli. Cyfidine deaminase cdd gene was deleted from an E. coli AU39 wild type strain to develop AU39 （Acdd）. Then homoserine dehydrogenase gene （thrA） was deleted from an AU39 （Acdd） strain to develop AU39 （AcddAthrA）, the intmcellular concentration of aspartate was expected to be increased. Compared with the cyfidine production in AU39, the cytidine production in AU39 （AcdcO and AU39 （AcddAthrA） were increased by 1.25 and 1.6-folds. It was concluded that a cytidine-producing swain with a relatively high yield can be developed using a metabolic engineering approach.