Abstract:In this study, the improvement of L-threonine synthesis in E. coli was achieved by optimizing transport of glucose. The CRISPR gene-editing method was used to delete the key genes ptsH and ptsG in the PTS system. The flask fermentation was carried out under 30 g/L glucose.Compared with the control strain TWF001, the productivity of L-threonine synthesis was significantly improved in either TWF001ΔptsH or TWF001ΔptsG, and the L-threonine yield of TWF001ΔptsH increased 38.02%. The strains TWF001ΔptsH, Ptrc::PgalP were successfully constructed via the enhancement of galP expression though adding the trc promoter in TWF001ΔptsH genome.Three mutant strains were grown by flask fermentation under 40, 50 or 60 g/L glucose, respectively. The fermentation yield of L-threonine in TWF001ΔptsH, Ptrc::PgalP after 36 h increased by 42.12%, which was 26.16 g/L with a sugar acid conversion rate of 0.65 g/g. The modification of glucose transport was confirmed to effectively improve L-threonine synthesis in E. coli.
