Integrated synthetic approach of metabolic engineering to produce L-tryptophan from Escherichia coli

View all posters

SungHo Jang, Sang Woo Seo, Gyoo Yeol Jung*

Pohang University of Science and Technology, South Korea

Metabolic engineering of microorganisms has been traditionally relied on rational approach based on detailed knowledge of the producing host and the target pathway. However, combinatorial approach also has been proving its ability in metabolic engineering by utilizing nature’s genuine mechanism, diversification and selection. Current limitations of rational and combinatorial approach are fine and predictive expression of pathway enzymes and screening of superior and optimized variant out of vast library, respectively. Here, we present an integrated synthetic biology approach which settled the problems of rational and combinatorial approach to produce L-tryptophan from Escherichia coli. First, we removed known bottlenecks on L-tryptophan synthesis pathway by using a predictive model of protein expression level, UTR Designer, which can precisely predict expression level of enzyme based on folding energy of specific features in mRNA secondary structure. UTR sequences of bottleneck enzymes were re-designed to maximize the metabolic flux through the pathway. Then we optimized the producing strain by utilizing a riboswitch-based screening tool, riboselector, which modulates expression level of selective marker gene in response to the target molecule. Riboselector for L-tryptophan was able to enrich superior variants out of vast library which were constructed from rationally engineered strain. We claim here that remarkable producing strains could be obtained through integrated synthetic biology approach by resolving pre-existing problems of metabolic engineering.