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以硫霉素产生菌卡特利链霉菌３５８（Ｓｔｒｅｐｔｏｍｙｃｅｓｃａｔｌｅｙａ３５８）为原始菌株，用原生质体形成与再生结合物理、化学诱变的方法进行菌种选育。在最适条件下原生质体释放浓度和再生率分别为１．６×１０９／ｍｌ和２９．５％。原生质体再生处理后，硫霉素产量变异向正方向移动，筛选到１株ＰＲ－１１７，相对效价提高６０％。分别以菌株ＰＲ－１１７的孢子和原生质体进行紫外线及亚硫酸氢钠诱变，原生质体对诱变剂的敏感性强于孢子，致死率增加，效价分布更分散。原生质体与孢子紫外线诱变正变率分别为１６．５％和９％，亚硫酸氢钠诱变的正变率都为４％。从原生质体紫外线诱变株中筛选到１株ＰＲｕ－３３６，相对效价比原始菌株提高９０％。
Streptomyces catleya 358 was used as the original strain, and strain selection was carried out by protoplast formation and regeneration combined with physical and chemical mutagenesis. Protoplast release concentration and regeneration rate under the optimal conditions were 1.6 × 109 / ml and 29.5%, respectively. After protoplast regeneration, the variation of the yield of thiophanin was shifted in the positive direction. One PR-117 strain was screened, and the relative potency increased by 60%. The spores and protoplasts of strain PR-117 were respectively mutagenized by UV and sodium bisulfite. Protoplasts were more sensitive to mutagens than spores, resulting in more lethality and more dispersed titers. The positive rate of UV mutagenesis of protoplasts and spores was 16.5% and 9% respectively, and the positive rate of sodium bisulfite mutagenesis was 4%. A PRu-336 strain was screened from the protoplast UV mutagens. The relative potency of PRu-336 was 90% higher than that of the original strain.