Exploring the metabolic fate of propanol in industrial
erythromycin-producing strain via 13C labeling experiments and
enhancement of erythromycin production by rational metabolic engineering
of Saccharopolyspora erythraea
Abstract
Propanol have been widely used as a precursor for erythromycin synthesis
in industrial production. However, the knowledge on the exact metabolic
fate of propanol was still unclear. In the present study, the metabolic
fate of propanol in industrial erythromycin-producing strain S.
erythraea E3 was explored via 13C labeling experiments. An unexpected
pathway in which propanol was channeled into tricarboxylic acid cycle
was uncovered, resulting in uneconomic catabolism of propanol. By
deleting the sucC gene, which encodes succinyl-CoA synthetase that
catalyse a reaction in the unexpected propanol utilization pathway, a
novel strain E3-ΔsucC was constructed. The strain E3-ΔsucC showed a
significant enhancement in erythromycin production in the chemically
defined medium compared to E3 (786.61 vs 392.94 mg/L). Isotopic dilution
mass spectrometry metabolomics and isotopically nonstationary 13C
metabolic flux analysis were employed to characterize the metabolic
differences between S. erythraea E3 and E3-ΔsucC. The results showed
that compared with the starting strain E3, the fluxes of pentose
phosphate pathway in E3-△sucC increased by almost 200%. The most
significant difference located in the tricarboxylic acid cycle was also
found. The flux of the metabolic reaction catalyzed by succinyl-CoA
synthetase in E3-ΔsucC was almost zero, while the glyoxylate bypass flux
significantly increased. These new insights into the precursor
utilization of antibiotic biosynthesis by rational metabolic engineering
in S. erythraea provide the new vision in increasing industrial
production of secondary metabolites.