Deletion of regulator-encoding genes fadR, fabR and iclR to increase L-threonine production in Escherichia coli

Recombination, Genetic Threonine 0301 basic medicine Escherichia coli Proteins 3. Good health Repressor Proteins Mutagenesis, Insertional 03 medical and health sciences Glucose Bacterial Proteins Metabolic Engineering Fermentation Escherichia coli Gene Deletion Transcription Factors
DOI: 10.1007/s00253-019-09818-8 Publication Date: 2019-04-18T09:27:51Z
ABSTRACT
Previously, we have developed an L-threonine-producing Escherichia coli strain TWF006 in which the regulator-encoding gene iclR was deleted. In this study, further modifications were performed on TWF006 to increase L-threonine yield. Firstly, the regulator-encoding gene fadR was deleted in TWF006, and the resulting strain TWF031 produced 18.86 g L-threonine from 30 g glucose after 24-h cultivation. Secondly, the regulator-encoding genes fabR and lacI in TWF031 were deleted, and the resulting strain TWF033 produced 19.21 g L-threonine from 30 g glucose after 24-h cultivation. Thirdly, additional copies of aceBA and fadBA were inserted into the lacZ locus of TWF033 and the native promoter of acs was replaced by the Ptac-trc; the resulting strain TWF038 produced 20.3 g L-threonine from 30 g glucose after 24-h cultivation. Finally, the genes ppnK, thrA*BC-rhtC, aspC, and ppc were inserted into the chromosome of TWF038; the resulting strain TWF044 produced 21.64 g L-threonine from 30 g glucose, or 28.49 g L-threonine from 40 g glucose after 24-h cultivation. After 48-h fed-batch fermentation, TWF044 produced 103.89 g/l L-threonine. The results suggest that coupling the fatty acid degradation and L-threonine biosynthesis pathway via the glyoxylate shunt could efficiently increase L-threonine production in E. coli.
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