Influence of divalent ions on the solubility of iturin and bacillomycin L, antifungal peptidolipids of Bacillus subtilis.

When calcium chloride was added to the culture medium of strains producing iturin or bacillomycin L, the antibiotic, normally excreted in the supernatant of the culture medium, was found in the cell pellet. This apparent inhibition of the antibiotic excretion was studied and it was demonstrated that CaCl2 precipitated the antibiotic after its excretion in the medium. The ability of various chloride salts to precipitate iturin and bacillomycin L was tested and the most effective salts were CaCl2 and MnCl2. Comparison of the compounds obtained by CaCl2 precipitation and by acid precipitation showed that, in the latter case, major antibiotics were accompanied by minor congeners resulting from modifications of genuine antibiotics.