Putrescine, 1,4-diaminobutane, is a valuable chemical compound which has highpotential to be applied in chemical industry. Especially, putrescine can be polymerizedwith adipic acid synthesizing nylon-4,6. Like this, biosynthesis of putrescine fromrenewable sources can substitute chemical compound synthesized from petroleum.Previously, Escherichia coli was developed to produce putrescine by knockout andoverexpression of genes in constructed pathway. We supposed that this strain can befurther improved by using small regulatory RNA system, which is recently developedgene knockdown tool. With this gene regulatory system, we blocked competitivepathway and increased the flux toward target chemical, putrescine. The culturecondition was also optimized following the enhanced production rate of putrescine. As aresult, the productivity, production yield and titer were all increased significantly. [Thiswork was supported by the Technology Development Program to Solve ClimateChanges on Systems Metabolic Engineering for Biorefineries of the Ministry of Education, Science and Technology (MEST)through the National Research Foundation of Korea.]