Change in colony morphology and kinetics of tylosin production after UV and gamma irradiation mutagenesis of Streptomyces fradiae NRRL-2702

Tylosin is a macrolide antibiotic used as veterinary drug and growth promoter. Attempts were made for hyper production of tylosin by a strain of Streptomyces fradiae NRRL-2702 through irradiation mutagenesis. Ultraviolet (UV) irradiation of wild-type strain caused development of six morphologically altered colony types on agar plates. After screening using Bacillus subtilis bioassay only morphological mutants indicated the production of tylosin. An increase of 2.7 +/- 0.22-fold in tylosin 7 production (1500 mg/l) in case of mutant UV-2 in complex medium was achieved as compared to wild-type strain (550 mg/l). Gamma irradiation of mutant UV-2 using Co-60 gave one morphologically altered colony type gamma-1, which gave 2500 mg/l tylosin yield in complex medium. Chemically defined media promoted tylosin production upto 3800 mg/L. Maximum value of q(p) (3.34 mg/gh) was observed by mutant gamma-1 as compared to wild strain (0.81 mg/gh). Moreover, UV irradiation associated changes were unstable with toss of tylosin activity whereas mutant gamma-1 displayed high stability on subsequent culturing. (c) 2007 Elsevier GmbH. All rights reserved.