A new cyclic dipeptide from peptone.

WHILE investigating the antifungal principle derived from cultures of a Bacillus subtilis strain, a crystalline substance was obtained as one of the byproducts. It was necessary to decide whether the crystals were a metabolite of the organism or originally contained in peptone used as a dietary essential. The same procedure succeeded in isolating the same crystals from peptone. The peptone was commercially available as ‘Mikuni peptone’ in Japan.