ABSTRACT
After testing the resistance of streptomycin to NS-41-80 Streptomyces Nanchangensis NS-41-80, the spores treated with 4 different dosage of super-mutagent EMS were regenerated on the lethal media, thus 3,000 streptomycin-resistant ( str ) str mutants were obtained. Then 202 spore mutants were screened through the pre-screening experiments and their yields are beyond 20% higher than the original strains respectively. In the re-screening experiments 48, 7 and 1 mutants were obtained whose yields are 100%, 200% and 300% higher than the original strains respectively and take the precentage of 23.76% and 1.60%, 3.46% and 0.23% and 0.5% and 0.03% of the number of the pre-screened strains and the rescreened strains respectively. Then 5 mutants were fermented whose yields are above 240% higher and the original strain through the continuous 3 batches fermentation, the yields are 57%～96.4% more than the original strains. Among them the yield of 80-5.3-165 is upwards of 6,000?g/mL and its norm is 5,855?g/mL. And a model of the streptomycin-resistance mutational screening of the strain producing Nanchangmycin was established.