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Metabolic engineering of E. coli for efficient production of glycolic acid from glucose

Deng, Yu, Mao, Yin, Zhang, Xiaojuan
Biochemical engineering journal 2015 v.103 pp. 256-262
DNA, Escherichia coli, aeration, batch fermentation, bioreactors, chromosomes, culture flasks, gene overexpression, genes, glucose, glycolic acid, glyoxylate cycle, homologous recombination, isocitrate dehydrogenase, isocitrate lyase, malate synthase, metabolic engineering, mixing, mutants
Glycolic acid is the smallest member of the α-hydroxy acid family. In order to produce glycolate from glucose via the glyoxylate shunt stably, one malate synthase gene aceB in Escherichia coli BW25113 was deleted by homologous recombination; another malate synthase gene glcB was then replaced by a DNA cassette WAK harboring isocitrate lyase gene (aceA), glyoxylate reductase gene (ycdW) and isocitrate dehydrogenase kinase/phosphatase gene (aceK). The above three genes were over-expressed in the chromosome of E. coli EYX-1WAK. This strain was then transferred 20 times on M9 medium to have a mutant strain: EYX-2 with a significantly improved growth rate. The glycolate yields of EYX-2 in the shaken flasks and the 5-L bioreactor using batch fermentation strategy under 2vvm aeration and 800rpm stirring speed were 0.33g/g-glucose and 0.48g/g-glucose, respectively. The fed-batch fermentation of EYX-2 on 120g/L glucose had the highest titer of 56.44g/L with 0.52g/g-glucose yield in 120h, and this is the highest reported glycolate yield ever.