[Effect of antibiotics on 5'-inosinic acid biosynthesis by a Brevibacterium ammoniagenes mutant].

The effect of streptomycin, erythromycin, kanamycin and penicillin on the biosynthesis of 5'-inosinic acid (IMP) by the mutant strain Brevibacterium ammoniagenes was studied. It has been found that the efficiency of antibiotic action depends not only in its concentration but on the age of the culture. When the antibiotics were introduced into the culture broth at the beginning of fermentation, they inhibited the culture growth and accumulation of IMP in the cultural medium. Only after 36-72 hours of cultivation the addition of the antibiotics stimulated the biosynthesis. All the antibiotics tested when adding at the definite for each of them period of fermentation and at the definite concentration stimulated the accumulation of IMP. The stimulating effect appears to be connected with an increase in permeability. A considerable increase in the number of anormalous elongated and swollen cells and, as a rule, in the protein content of the cultural supernatant indicates the fact. Streptomycin and kanamycin were the most efficient antibiotics, as they increased the IMP yield from 10.4 to 17.5 g/l.