[Effect of nitrogen-containing compounds on the biosynthesis of avermectins].

: The influence of complex nitrogen-containing substrates (Difko yeast extract, EKD nutrient yeast extract, soy bean flour and cotton seed meal), ammonium salts and some amino acids (alanine, methionine, valine, isoleucine and threonine) on the biosynthesis of avermectins in the cultures of two mutants of Streptomyces avermitilis was studied. It was shown that an excess of the nitrogen compounds in the fermentation medium induced a decrease in the antibiotic biosynthesis and the relative content of the group B avermectins.