Breeding and fermentation condition optimization of L-histidine producing strain

The Serratia marcescens ATCC 31026 was used as the starting strain.By stepwise mutagenic treatments with Nmethyl-N-nitro-N-nitrosoguanidine(NTG),diethylsulfate(DES) and ultraviolet(UV),the objective mutant ZJZ 625(AMT~r6-MP~rHE~r2-TU~r6-MEP~rDH~r) was obtained.The mutants was selected on the agar plates containing 3-amino-1,2,4triazole,6-mercaptopurine arabinoside,L-histidine methyl ester dihydrochloride,2-thiouracil and D-histidine.The L-histidine producing mutant ZJZ 625 could accumulate 7.6 g/L.Based on the effects of single factors and then the response surface analysis was used to optimize the concentrations of the substrate.The amount of L-histidine accumulation reached to a level of 9.7 g/L.