Improving gentamicin B and gentamicin C1a production by engineering the glycosyltransferases that transfer primary metabolites into secondary metabolites biosynthesis

Gentamicin B and gentamicin C1a are the direct precursor for Isepamicin and Etimicin synthesis, respectively. Although producing strains have been improved for many years, both gentamicin B titer and gentamicin C1a titer in the fermentation are still low. Because all gentamicin components are biosynthesized using UDP-N-acetyl-d-glucosamine (UDP-GlcNAc) and UDP-xylose as precursors, we tried to explore strategies for development of strains capable of directing greater fluxes of these precursors into production of gentamicins. The glycosyltransferases KanM1 and GenM2, which are responsible for UDP-GlcNAc and UDP-xylose transfer, respectively, were overexpressed in gentamicin B producing strain Micromonospora echinospora JK4. It was found that gentamicin B could be improved by up to 54% with improvement of KanM1 and GenM2 expression during appropriately glucose feeding. To prove this strategy is widely usable, the KanM1 and GenM2 were also overexpressed in gentamicin C1a producing strain, titers of gentamicin C1a improved by 45% when compared with titers of the starting strain. These results demonstrated overexpression the glycosyltransferases that transfer primary metabolites into secondary metabolites is workable for improvement of gentamicins production.