Multistep construction of metabolically engineered Escherichia coli for enhanced cytidine biosynthesis

In this study, the systematic construction of metabolically engineered Escherichia coli strain for cytidine over-production was investigated, where the regulation of downstream pathway from uridine monophosphate (UMP) toward cytidine was focused on. Firstly, the engineered strain CR016 obtained by deleting the cytidine catabolism-related genes in E. coli MG1655 showed a significantly slower degradation rate of cytidine. Further modifications were carried out to amplify the metabolic flux from UMP to cytidine. The resulted strain CR023(pTrc03) began to accumulate 352.59 mg/L of cytidine in shake flask culture for 36 hr. After optimizing the supply of three precursors, the final engineered strain CR023(pTrc03/pBAD021) produced 704.19 mg/L of cytidine with a yield of 0.15 g/g glucose, upon the supplementation with 2 mM glutamate. A fed-batch fermentation was then performed in a 5-L reactor to increase cytidine titer by 11.13-fold to 7.84 g/L in 48 hr. The multistep metabolic engineering strategies presented here enabled a stepwise increase in the production of cytidine.Graphical abstract
Source: Biochemical Engineering Journal - Category: Biochemistry Source Type: research