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Metabolic Engineering of Escherichia coli for Production of Tyrosine and Cadaverine through Microbial Gene Repression System Using the Synthetic Small RNAs

Small regulatory RNAs (sRNAs) are gene expression regulators which act on post-transcriptional phase of bacterial gene expression. Here, we developed a synthetic small regulatory RNA system to down-regulate gene expression. The target mRNA binding region of MicC, one of the well-studied sRNAs in Escherichia coli, was replaced to translation initiation sequence of our target genes. We found that MicC scaffold based synthetic sRNA properly repressed expression of DsRed2, a fluorescence protein. Synthetic sRNAs were applied to metabolic engineering to enhance the production of tyrosine and cadaverine. Through screening of 14 different strains, harboring one or combination of the synthetic sRNAs targeting ppc, tyrR, csrA, and pgi, we isolated a tyrosine producer producing 2 g per liter of tyrosine. Using a library of 130 synthetic sRNAs, we screened knockdown targets that increase cadaverine productivity substantially. Repression of murE led to 55% increase in cadaverine production compared to the base strain. [This work was supported by the Technology Development Program to Solve Climate Changes on Systems Metabolic Engineering for Biorefineries from the Ministry of Science, ICT and Future Planning (MSIP) through the National Research Foundation (NRF) of Korea (NRF-2012M1A2A2026556 and NRF-2012M1A2A2026557); the Intelligent Synthetic Biology Center through the Global Frontier Project (2011-0031963) of the Ministry of Education, Science and Technology (MEST) through the National Research Foundation of Korea]