[Effect of aromatic amino acids on levorin biosynthesis].

Aromatic amino acids, such as tryptophan and phenylalanine inhibit biosynthesis of levorin, while tyrosine stimulates it. The studies with resting cells showed that the changes in the level of the antibiotic production in the presence of the above amino acids were connected with their effect on the process of levorin biosynthesis and not on the growth of the antibiotic-producing organism. The changes in the content of the bound p-aminoacetophenone in the mycelium of Str.

[Role of p-aminobenzoic acid in levorin biosynthesis].

The effect of p-aminobenzoic acid on the biosynthesis of levorin was studied. It was shown that in the presence of exogenic p-aminobenzoic acid the antibiotic activity increased by 11 per cent. The acid added was transformed into p-aminoacetophenone which was partially used for levorin synthesis and partially accumulated in the mycelium in a free state.

[Determination of p-aminoacetophenone and changes in its levels in a levorin producer depending on culture conditions].

A method for spectrophotometric determination of p-aminoacetophenone (p-AAP) in the mycelium and fermentation broth filtrates of organisms producing polyenic macrolide antibiotics is described. The level of p-AAP accumulation was studied as applicable to the biosynthesis of levorin, a polyenic antibiotic of the heptaen series. The levels of p-AAP under usual conditions of the levorin-producing organism cultivation and under conditions of its stimulation with the products of the vital activity of yeast-like fungi were compared.