Enhancement of tylosin production in Streptomyces fradiae by Mutation

In order to increase tylosin production by Streptomyces fradiae، two mutagens، i. e. uv and EMS (Ethylmethanesulfonate) were used. Death curves were plotted for these mutagens. Optimum condition for obtaining mutants by uv radiation was determined by using a uv source lamp at a distance of 20 cm for 40-60 seconds. When EMS was used at 4% (w/v) concentration، the best mutants were isolated after 30 minutes of exposure to the mutagen. In the first mutation step، which was done by uv radiation، high tylosin producing strains were isolated by Plaque Agar method as the first screening step. For the second step of screening، a mutant strain (U24) with a production of 0. 892 mg tylosin per ml was isolated، which was 1. 27 times more productive than the wild type. The secondary mutation step on this mutant strain was performed by EMS. Finally، a mutant strain (UE1) with a production of 2. 18 mg tylosin per ml was obtained، which was 3. 12 times more productive than the wild type.