Muconic Acid Production Using Gene-Level Fusion Proteins in Escherichia coli

This study reports on the improving of muconic acid (MA) production by using metabolically engineered Escherichia coli. Three MA synthesis pathways separately were introduced into E. coli. After 72 h of cultivation, two of the three strains, i.e., one carrying the Pathway 1 (1.00 g/L) and the other carrying the Pathway 3 (1.34 g/L) produced MA. To increase MA production, the enzymes of the shikimate pathway (AroC and AroD) were overexpressed in these strains. Although the overexpression of AroC increased the MA production (1.59 g/L) by the Pathway 1, AroD overexpression decreased it by the Pathway 3. The metabolic channeling using gene-level fusion proteins additionally increased the MA production. In the pathway 1 and pH-controlled cultures, the overexpression of a fusion protein (AroC and MenF) increased the MA production from 20 g/L glucose to >3 and 4.45 g/L, respectively. These results suggest that the metabolic channeling approach is a promising strategy to increase the yield of the target compound.