Enhancement and Cultural Characteristics of Leucomycin Production by Streptomyces kitasatoensis in the Presence of Magnesium Phosphate

Stimulation of leucomycin production with Streptomyces kitasatoensis by magnesium phosphate (MgP), and a concomitant decrease of ammonium ion concentration in the culture supernatant have been reported from this laboratory. Cultural characteristics of the MgP-supplemented culture were further examined in relation to the stimulation of leucomycin production. When the leucomycin titer increased 4- to 5-fold in the presence of MgP, mycelial growth level and assimilation rate of a major carbon source (glycerol) increased about 2-fold. MgP-grown mycelia were not appreciably different in shape or in carbon and nitrogen contents from the control mycelia. Magnesium and phosphate ions were released from MgP into the medium, while the addition of magnesium or phosphate salts to the control medium was rather inhibitory for leucomycin production. The pH values of MgP-supplemented cultures were lower than those of the control culture. When modifications of the basal media and culture conditions were done so as to permit the pH-change almost identical with that of the control media, the leucomycin titer was still higher in the presence of MgP than in its absence. When uric acid, an insoluble compound, was used as the sole nitrogen source, the leucomycin production increased to a high level even in the absence of MgP, which was comparable to that seen when MgP was added to the ammonium lactate-containing medium. The ammonium ion concentration in the culture supernatant of the uric acid-containing medium was maintained at a considerably low level. While in the ammonium lactate-containing medium, leucomycin production was low and ammonium ion concentration remained at a high level. Thus, it was demonstrated that the stimulation of leucomycin production by MgP is related to the lowering of ammonium ion level, but not to the other factors examined such as growth level, carbon or phosphate regulation and pH-effect.