In the previous reports^1,2), the author described his studies on the improvement of the strain for the capacity of pyridomycin production. The lactose-utilizing mutants of Streptomyces pyridomyceticus had the high capacity, and the mutant having the highest capacity for pyridomycin production utilized tryptophan as the carbon source. In this paper, media suitable for pyridomycin production and a method of detecting precursors of pyridomycin are presented. This method is considered to be applicable to precursor studies of antibiotics in general.

Among natural products soybean meal was one of the nitrogen sources suitable for pyridomycin production, and among carbohydrates glucose was a suitable carbon source. The addition of phosphate promoted the production. Thus, a complex medium suitable for the practical production of pyridomycin was established. In synthetic media containing glucose and inorganic salts, pyridomycin was produced, when aspartic acid, glutamic acid, asparagine or ammonium phosphate was used as the nitrogen source in the presence of pyridoxine. In the medium containing aspartic acid or glutamic acid with pyridoxine and inorganic salts, pyridomycin was produced, when glucose, gluconic acid, or arabinose was used as the carbon source. The cotton pin method of detecting precursors indicated that there were four kinds of substances promoting pyridomycin production in 40 hours’ shaken-cultured liquid of the pyridomycin-producing strain. Three of them were confirmed to be serine, tryptophan and kynurenine by paper chromatography. The other one was not identified yet, but it has a similar ultraviolet absorption spectrum to that of pyridomycin.

The present studies suggested that, when glucose was metabolized through gluconate and pentose, pyridomycin would be produced, and tryptophan metabolism would have relations to pyridomycin production. Maeda³⁾ confirmed the existence of pyridine nucleus in pyridomycin, and this part is considered to be built through tryptophan.