[Metabolic products of microorganisms. 166. Optimization of the desferri-ferricrocin production by Aspergillus viridi-nutans Ducker & Thrower (author's transl)].

At low iron(III)-concentrations (less than 10(-5) M) the fungus Aspergillus viridi-nutans Ducker & Thrower excretes desferri-ferricrocin as the main sideramine into the culture medium. While this compound accounts for 95% of the sideramines produced, small amounts of additional sideramines may also be detected. In a search for an inexpensive nutrient medium for optimum production of desferri-ferricrocin, experiments using shake flasks with good aeration were undertaken initially. The best medium conditions were then employed in a fermentor system. In a 20-1 fermentor with "intensor" system, it was shown that at certain growth rates there was an inverse correlation between rate of growth and rate of sideramine production. A defined nutrient medium of glucose plus acetate as carbon sources, and urea or ammonium acetate as nitrogen sources was used. Two different feeding regimens were used in response to changes of pH or to changes of partial pressure of oxygen in the submerged culture: acetic acid/urea or acetic acid/ammonium acetate additions regulated these conditions. The rate of sideramine production under such feeding achieved a maximum of 20 mg 1(-1) h-1 over a period of several days.