earticle

영어

Although great progress has been made in rational approach, strain improvement still requires the optimization of the biological system itself. Combinatorial approach is, however, limited by the method isolating high producer from the library. Among the various methods available currently, selection by the physiology associated with the growth is known to be the most efficient since high producer can be easily enriched simply by a serial culture. However, most physiological features to be improved such as biochemical productions are not easily associated with the growth and consequently, tedious screening process should be only technique to select high producer out of the library. In this study, we developed a RNA device to express as a selective phenotype with response to the intracellular biochemical level which is not associated with the growth against the selective pressure. As a model, lysine synthetic pathway was optimized in E. coli. For the optimization of lysine synthesis, downstream lysine synthesis pathway from oxaloacetate to lysine was upregulated by re- designing the promoters and 5’-untranslated regions of the gene in the downstream lysine synthesis pathway. In addition, anaplerotic pathway catalyzed by PEP carboxylase encoded by ppc was re-optimized by selection of its optimal expression level among the promoter library. By combining RNA device which responds to the intracellular lysine level, optimal ppc expression level for lysine synthesis was easily selected. A physiological study demonstrated that the performance of optimized ppc variant on lysine production compared to its parental strain.