利福霉素B产生菌─—地中海诺卡氏菌的推理选育

利福霉素Ｂ的生物合成受芳香族氨基酸（Ｔｒｐ、Ｔｙｒ、Ｐｈｅ）的反馈抑制。用紫外线处理Ｎ．ｍｅｄｉｔｅｒｒａｎｅｉＸＣ－１０２菌丝悬浮液后，并在含０．１％芳香族氨基酸的琼脂平板上分离芳香族氨基酸抗性变种。结果表明，芳香族氨基酸抗性变种的发酵效价高于自然分离株和紫外线诱变株；色氨酸抗性变种（Ｔｒｐｒ）的发酵效价又高于酪氨酸抗性变种（Ｔｙｒｒ）和苯丙氨酸抗性变种（Ｐｈｅｒ）；０．５％Ｔｒｐｒ变种比０．１％Ｔｒｐｒ变种更高产。其中０．５％Ｔｒｐｒ变种ＸＣ－５４０的生产能力较出发菌株ＸＣ－１０２增加４２．１６％。传代试验表明ＸＣ－５４０的遗传特性稳定，在７ｍ３罐做发酵放大，与出发菌株相比，发酵效价和发酵指数分别提高５１．１１％和５１．０２％。

Rational selection of rifamycin B producing strain Nocardia mediterranei

Biosvnthesis of rifamvcin B was inhibited by the aromatic amino acids:phenylalanine(Phe),tyrosine(Tyr),and tryptophan(Trp). When the mycelium suspensionof N.mediterranei XC-102 was treated with U.V., we isolated the aromatic amino acidresistant mutant strains which could grow on the agar plates containing 0. 1% aromatic amino acids.The aromatic amino acid resistant mutantstrains produced niore rifaniycin B than the parent strain and U. V. mutants. Moreover,theTrpr mutants produced more rifamycin B than the Pher and Tyrr mutants,respectively. The0. 5% Trpr mutants had higher yield than the 0. 1% Trpr mutants. Among them, theproductivity of the 0.5%Trpr mutant strain XC-540 was increaed 42.16% more than that ofthe parent strain XC-102.Subculture test indicated that the heredity character of XC-540 was stable. Thefermentation of XC-540 was performed in 7m3 fermenter,and it made the potency and indexof fermentation increased by 51.11% and 51.02%,respectively.