Metabolic Engineering for the Heterologous Biosynthesis of Erythromycin A and Associated Polyketide Products in Escherichia coli.
Abstract: The natural
product erythromycin is a potent and widely used antibiotic for bacterial infections. In
structure, erythromycin consists of one 14-membered polyketide ring,
6-deoxy-erythronolide B (6dEB), and two sugar residues, cladinose and desosamine.
Erythromycin is natively produced by a soil-dwelling bacterium Saccharopolyspora
erythraea that is fastidious in its growth requireme... read morents and hard to manipulate through
genetic and metabolic engineering approaches. In this thesis study, the production of
the erythromycin polyketide precursor 6dEB was optimized by engineering the Escherichia
coli native metabolic pathways to support biosynthesis of the required substrates.
Furthermore, heterologous biosynthesis of the erythromycin sugar groups cladinose and
desosamine was achieved to produce the final product erythromycin A in E. coli. The
reported titer for erythromycin A was ~10 mg/L. The entire 55kb erythromycin producing
gene cluster was then systematically transferred to E. coli to enable the complete
heterologous biosynthesis of erythromycin from propionate. Lastly, novel erythromycin
associated polyketide analogs were produced by modification of the polyketide and sugar
moiety biosynthetic pathways in E. coli. The resulting products contained altered
polyketide or sugar groups, as directed by the rationally designed new biosynthetic
pathway. Success establishes E. coli as a viable option for the heterologous production
of erythromycin A and, more broadly, as a platform for the directed production of
erythromycin associated polyketide analogs.
Thesis (Ph.D.)--Tufts University, 2011.
Submitted to the Dept. of Chemical and Biological Engineering.
Advisor: Blaine Pfeifer.
Committee: Andrew Wright, Marcia Osburne, and Kyongbum Lee.
Keyword: Chemical Engineering.read less