L-Tyrosine is a commercially important compound because it is used as the precursors of the pharmaceutical drugs and the other valuable chemicals such as flavonoids and alkaloids. Microbial production has great potential due to better understanding on genetic information, the various engineering tools, and simple scale-up process. For several decades, many attempts for L-tyrosine production by microorganisms were made to increase L-tyrosine production such as overexpression of pathway enzymes, modulation and deregulation of repressors, and global transcriptional machinery engineering. However, these efforts were not sufficient to maximize enzyme expression level due to lack of understanding expression level control at translational level and the fact that flux more than necessary toward L-tyrosine biosynthesis pathway could hamper cell growth with reduced TCA cycle activity. To optimize metabolic pathway, precise control of expression level for pathway enzymes was conducted by UTR engineering which is re-design of nascent UTR to obtain desired expression level. With this manner, expression level of linear pathway enzymes can be maximized and expression level of the key enzyme determining carbon flux for cell growth and production can be fine-tuned for the maximum production.In this study, nascent genetic elements of L-tyrosine biosynthesis enzymes were replaced by synthetic promoters and 5'UTR designed for maximum expression. Additionally, carbon flux around cell growth and production at PEP node was optimized by testing various expression levels of ppsA. Finally, we could obtain the strain with 0.4g/L titer and 8.9mg�L-1�h-1�OD600-1 productivity while production of wild type is not negligible. This work demonstrated that pathway optimization by UTR redesign can be effective strategy for developing L-tyrosine high producer.

Pathway optimization by re-design of untranslated regions for L-tyrosine production in <i>Escherichia coli</i>

247th National Meeting (2014)

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Pathway optimization by re-design of untranslated regions for L-tyrosine production in Escherichia coli