Abstract:
Aim :To obtain a mutant which could increase the yield of cytidine by decreasing the feedback-inhibition of CTP synthetase.
Methods :A cytidine deaminase deficient strain was induced mutation by nitrosoguanidine(NTG) and screened with pyrimidine analogs,to obtain 6-azauracil,5-fluorocytidine and 3-deazauracil resistant strains.
Results :A mutant of
Bacillus subtilis K-215 was obtained,with the critical resistance concentration to 6-azauracil,5-fluorocytidine and 3-deazauracil being 0.9,3.5 and 4.5 mg/mL,respectively.The CTP synthetase activity of the mutant was increased by 5.2 fold and cytidine was accumulated to 6.2 mg/mL after 72 h fermentation at 37 ℃.
Conclusion :The mutant K-215 has higher cytidine productivity and is partially free from the feedback-inhibition on CTP synthetase.