Oxygen limitation can induce microbial secondary metabolite formation: investigations with miniature electrodes in shaker and bioreactor culture

Article Abstract:

A study of the activation of secondary metabolism due to time-dependent oxygen limitation in Amycolatopsis orientalis and Saccharopolyspora erythraea culturing by measuring dissolved oxygen levels using a miniature electrode reveals that the synthesis of erythromycin occurs under both well-aerated and oxygen-restricted conditions in inclined tube and shaken flask cultures of S. erythraea, while a novel secondary metabolite is synthesized under oxygen-restricted conditions alone. Oxygen-rich cultures of A. orientalis synthesize vancomycin and in batch bioreactor cultures. Oxygen restriction resembles substrate restriction due to dissolved nutrients in activating secondary metabolite synthesis in some cultures and suppressing it in others.

Physiological aspects, Oxygen, Bacteria

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The physiology of erythromycin biosynthesis in cyclic fed batch culture

Article Abstract:

The production of erythromycin by Saccharopolyspora (S.) erythraea in cyclic fed batch cultures depends on the specific growth rate at the beginning and during the cycle. A steady state occurs when a medium flow begins after the first increase in biomass of the culture. Antibiotic and gravimetric productivity increase with an increase in the growth-limiting substrates and dilution of the medium. Erythromycin is a secondary metabolite which evolves when the specific growth rate of S. erythraea begins decreasing. Erythromycin prepared by this method is more productive compared to batch cultures. Chemostat culture is less productive than batch culture.

Production management, Microbiological synthesis

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Effect of hyphal micromorphology on bioreactor performance of antibiotic-producing Saccharopolyspora erythraea cultures

Article Abstract:

A fragment of Saccharopolyspora erythraea hypha must exceed the critical hyphal fragment diameter of 88 micrometer to be able to produce antibiotic. This is because the antibiotic producing site occurs at a fixed distance from the growing hyphal tip. During batch culture production potential is dependent on culture development. Bioreactor stirrer speed affects antibiotic productivity as hyphal fragmentation rate is linearly associated with the energy supplied to the bioreactor (0.867 mg/mg biomass at 1500 r.p.m. and 0.913 mg/mg biomass at 750 r.p.m.).

Fungi, Morphology (Biology), Pharmaceutical microbiology

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