Mutation Breeding Of Carbamoyl-tobramycin High-yielding Strain And Studies On It's Fermentation And Metabolism

A tobramycin producing strain S.tenebrarius 9916 was mutated by NTG combined with tobramycin tolerance. A stable high-yielding mutant NTN201 was screened out. The total titer was increased from 439u/ml to 1143u/ml and the percentage of Carbamoyltobramycin(CTB) was increased from 74% to 88.5%. The total titer and the percentage of CTB were further increased to 1275u/ml and 92.6% respectively through optimum of the medium and the conditions for fermentation.The effects of sixteen anmino acids, quick-acting carbon and nitrogen sourses, phosphate and Fosfomycin on biosynthesis of CTB was observed. The total titer and the percentage of CTB were both increased when l0mmol/L Glu, Gly and a -keto-glutaramate were added to broth at 36h. Biosynthesis of CTB was repressed when instant carbon and nitrogen sources were up to high concentration as well as when 11.5mmol/L phosphate was added to broth at 36h. The total titer was promoted when Fosfomycin was added to broth at 36h.The regulative mechanism of NH4+ on biosynthesis of CTB were studied. It was indicated that NH4+ was transformed to incellular Glu which was the -NH2 donor for biosynthesis of CTB. The regulative mechanism of phosphate lies in two aspects, on one hand, L-glutamine: keto-scyllo-inositol aminotransferase was repressed by phosphate itself, on the other hand, phosphate was transformed to incellular ATP which regulate biosynthesis of Carbamoyltobramycin as an incellular effector.