【摘要】 以亚硝基胍（MNNG）诱变处理大肠杆菌AS1.358,获得蛋氨酸缺陷型（Met^-）突变株,从中得到一株B_23（?）1菌,能在培养基中积累少量苏氨酸。通过连续诱变,得K₁-73菌株（Met^-）,在5%葡萄糖与DL-蛋氨酸添加量为75mg/l的条件下,能够积累3.5mg/ml L-苏氨酸。同样以MNNG诱变处理钝齿棒状杆菌C.crenatum AS1.542,获得抗α-氨基-β-羟基戊酸(AHV^?)突变株1770株,其中6%菌株能够积累少量苏氨酸。选得LR-1（?）58菌产L-苏氨酸<1mg/ml。对该菌逐步诱变,得一株抗8mg/ml AHV及蛋氨酸缺陷型双重突变株(AHV^?,Met^-)LRA-96,其L-苏氨酸产率与亲株比较有明显提高,达3.5mg/ml。连续再诱变并结合单菌落分离选育,得一突变株m-85(AHV^?,Met^-),能在培养基中积累13mg/ml L-苏氨酸。试验表明,连续诱变处理是选育L-苏氨酸高产菌株有效手段之一。更多还原

【Abstract】 One hundred and fourteen strains of methionine auxotrophic mutants were derived from E. coli AS 1.385 by N-methylN’-nitrosoguanidine （MNNG） treatment, among them a mutant B₂₈₅₁ can accumulate small amount of L-threonine. By using B₂₈₅₁ as a starting strain for treatment, a threonine producing mutant K₁-73（Met^-） was obtained with stepwise induction, 3.5g/l of L-threonine was accumulated ina medium containing 5% glucose and 75 mg/l methionine.By the same way, 1770 strains of α-amino-β-hydroxy valerie acid （AHV） resistant mutant derived from C. crenatum AS 1.542 were obtained, L-threonine was produced by about 6% of those organisms, strain LR-1458 accumulated less than 1g/1 of L-threonine.Using LR-1458 as a starting strain for stepwise induction, an AHV resistant and methionine auxotrophic mutant （AHV^r, Met^-） LRA-96 was obtained, which can accumulate 3.5 g/l of L-threonine in the cultural broth. This yield is a four-fold increase compared with the starting strain LR-1458 （AHV^r）.A potent L-threonine producing mutant m-85 （AHV^r, Met^-） was obtained from LRA-96 by stepwise induction and single colony isolation. This strain produced 13 g/l of L-threonine. It has been proved that stepwise induction is effective artifice for breeding potent L-thrconine producer.更多还原