Screening of Dual Defects Strain and Effects on l-Isoleucine Production in Escherichia coli NML

Original strain Escherichia coli N12 with lifting the repression of l-isoleucine was mutated mutagenesis by diethylsulfate (DES), then l-isoleucine producing strain named E. coli NML were obtained. The effects of E. coli K12, N12, and NML in fermentation process on biomass, yield of l-isoleucine and glucose consumption rate were studied by carrying out fed-batch fermentation by analyzing the metabolic sysnthesis process. At 48 h, l-isoleucine production in the fermentation medium of N12 and NML was 2.25 and 4.64 g/L, respectively, and it was not detected in E. coli K12. Results show that mutant strains with dual genetic markers (Met− + Leu−) can help with the synthesis of l-isoleucine, which also provide some frame of reference for the production of other amino acids.