Metabolic engineering of Bacillus subtilis for high-level production of uridine from glucose

As an intermediate in drug synthesis, uridine has practical applications in the pharmaceutical field. Bacillus subtilis is used as a host to boost uridine yield by manipulating its uridine biosynthesis pathway. In this study, we engineered a high-uridine-producing strain of B. subtilis by modifying its metabolic pathways in vivo. Overexpression of the aspartate ammonia-lyase (ansB) gene increased the relative transcriptional level of ansB in B. subtilis TD320 by 13·18 times and improved uridine production to 15·13 g l^-1 after 72-h fermentation. Overexpression of the putative 6-phosphogluconolactonase (ykgB) gene increased uridine production by the derivative strain TD325 to 15·43 g l^-1 . Reducing the translation of the amido phosphoribosyl transferase (purF) gene and inducing expression of the subtilisin E (aprE) gene resulted in a 1·99-fold increase in uridine production after 24 h shaking. Finally, uridine production in the optimal strain B. subtilis TD335, which exhibited reduced urease expression, reached 17·9 g l^-1 with a yield of 314 mg of uridine g^-1 glucose. To our knowledge, this is the first study to obtain high-yield uridine-producing B. subtilis in a medium containing only three components (80 g l^-1 glucose, 20 g l^-1 yeast powder, and 20 g l^-1 urea).