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. Cytidine deaminase cdd gene was deleted from an E. coli AU39 wild type strain to develop AU39 (Δcdd). Then homoserine dehydrogenase gene (thrA) was deleted from an AU39 (Δcdd) strain to develop AU39 (ΔcddΔthrA), the intracellular concentration of aspartate was expected to be increased. Compared with the cytidine production in AU39, the cytidine production in AU39 (Δcdd) and AU39 (ΔcddΔthrA) were increased by 1.25 and 1.6-folds. It was concluded that a cytidine-producing strain with a relatively high yield can be developed using a metabolic engineering approach.

天津科技大学科学研究基金（20100211）