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Optimization of hexanoic acid production in recombinant Escherichia coli by precise flux rebalancing

Kim, Seong Gyeong, Jang, Sungho, Lim, Jae Hyung, Jeon, Byoung Seung, Kim, Jungyeon, Kim, Kyoung Heon, Sang, Byoung-In, Jung, Gyoo Yeol
Bioresource technology 2018 v.247 pp. 1253-1257
Cupriavidus necator, Escherichia coli, Megasphaera, acetyl coenzyme A, acetyl-CoA acetyltransferase, butyric acid, fermentation, genes, hexanoic acid, inoculum
The aim of this study is to demonstrate that rebalancing of metabolic fluxes at acetyl-CoA branch node can substantially improve the titer and productivity of hexanoic acid in recombinant Escherichia coli strains. First, a hexanoic acid-producing E. coli strain was constructed by expressing genes encoding β-ketothiolase (BktB) from Cupriavidus necator and acetyl-CoA transferase (ACT) from Megasphaera sp. MH in a butyric acid producer strain. Next, metabolic flux was optimized at the acetyl-CoA branch node by fine-tuning the expression level of the gene for acetyl-CoA acetyltransferase (AtoB). Four synthetic 5′-untranslated regions were designed for atoB using UTR Designer to modulate the expression level of the gene. Notably, the productivity of the optimized strain (14.7 mg/L/h) was the highest among recombinant E. coli strains in literature when using a similar inoculum size for fermentation. These results show that fine-tuning the expression level of atoB is critical for production of hexanoic acid.