Redirecting Metabolic Pathway By UTR Engineering to Improve L-Tyrosine Production in Escherichia coli

L-tyrosine is a commercially important compound in the food, pharmaceutical, chemical, and cosmetic industries. Microbial production of L-tyrosine have led to higher production yield of L-tyrosine, but it still remain to be achieve for optimizing the pathway such as translation-level expression control and carbon flux rebalancing around phosphoenolpyruvate (PEP) node. Here, we redirected metabolic pathway by altering gene expression levels to improve L-tyrosine production in Escherichia coli. To optimize the L-tyrosine biosynthetic pathway, a synthetic constitutive promoter and a synthetic 5′-untranslated region (5′-UTR) were introduced for each gene of interest to allow for control at both transcription and translation levels. Carbon flux rebalancing was achieved by controlling the expression level of PEP synthetase using UTR Designer. The L-tyrosine productivity of the engineered E. coli strain was increased through pathway optimization resulting in 3.0 g/L of L-tyrosine titer, 0.0354 g L-tyrosine/h/g DCW of productivity, and 0.102 g L-tyrosine/g glucose yield. Thus, this work demonstrates that metabolic pathway redirecting by UTR engineering is an effective strategy for improvement of L-tyrosine production.