Strain improvement of Streptomyces fradiae for the production of tylosin
1992
Sutisa Nittayu
Improvement of tylosin producing strain of S. fradiae, was carried out by using mutagen NTG with the optimal dose of 3,000 mg/ml for mutation of mycelium. The mutants were selected on AS-1 agar plus spectinomycin. The total of 27 mutants were selected and 9 mutants were found to be superior tylosin producers. The productivities vary between 0.94-1.26 mg/ml, comparision of 0.9 mg/ml of that of parent strain. When strain improvement was carried out from protoplasts only 100 mg/ml NTG was required. Twenty five of protoplast mutants were selected on AS-1 agar plus spectinomycin. From the mutants selected only 14 were found to be superior in tylosin producers with the productivities vary between 0.92-1.37 mg/ml. This study has also demonstrated that hybrids able of producing both antibiotics tylosin and tetracycline from protoplast fusion of S. fradiae and S. aureofaciens. Protoplasts were prepared using the cells treated with 5-10 mg/ml lysozyme for 2 hours, using 48 hours old culture. Using this method 6.7*10** (6) protoplasts/ml were obtained and were subsequently fused with the presense of 50 % PEG 6000. The hybrids regenerated and selected based on the morphological properties and only 23 hybrids were selected from the selective medium. Only 3 hybrids were found to produce significant amount of tylosin and tetracycline, the productivities varies between 0.55-0.65 mg/ml for tylosin and 1.17-1.24 mg/ml for tetracycline. The productivities from hybrids are higher than those from mixed culture. All the mutants and hybrids were able to produce tylosin and tetracycline in fermenter than in shake flask about 10 percent.
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