Thymidine production by overexpressing NAD⁺ kinase in an Escherichia coli recombinant strain

Intracellular NADPH/NADP⁺ ratio in cells grown on various production media with different carbon and nitrogen sources had a positive correlation with the thymidine production. To improve thymidine production in a previously engineered E. coli strain, NAD⁺ kinase was overexpressed in it resulting in the NADPH/NADP⁺ ratio shifting from 0.184 to 0.267. The [NADH + NADP⁺]/[NAD⁺ + NADPH] ratio was, however, not significantly altered. In jar fermentation, 740 mg thymidine l^-1 was produced in parental strain, while 940 mg l^-1 of thymidine was produced in NAD⁺ kinase-expressing strain.