Abstract
Streptomyces hygroscopicus No. B-5050-HA, which produces a mixture of six marido-mycins, yielded a mutant which produced 75% of the mixture as maridomycin III (MDM III). Growth of S. hygroscopicus No. B-5050-HA, an improved MDM producer, was almost completely inhibited by 20μg/ml of valine. This inhibition was counteracted by the addition of isoleucine, threonine, homoserine, methionine, α-amino-n-butyrate and α-ketobutyrate.
A valine resistant mutant, strain AV was isolated and found to produce increased level of MDM III at the expense of other maridomycins. Production of MDM III by the parent strain depended on the addition of isoleucine to the medium, but that by this mutant did not.
The properties of strain AV were discussed.
