Proficient production of the antitumor agent triostin A was developed using engineered Escherichia coli (E. coli). The bacterium played host to 15 genes that encode integral biosynthetic proteins which were identified and cloned from Streptomyces lasaliensis. In this study, triostin A production was dramatically increased by more than 20-fold, 13 mg/L; with the introduction of exogenous quinoxaline-2-carboxylic acid (QXC), the speculative starting unit for biosynthesis of triostin A. Conversely, de novo production of triostin A by means of high cell density fed-batch fermentation that is exclusive of exogenous QXC bore a modest amount of the antitumor agent. Noteworthy production of the biologically active molecule was achieved with small-scale cultivation and quantitative analysis of the product was accomplished with a liquid chromatography-mass spectrometer. This simple and speedy system could easily provide us with valuable information for maximizing the production titer. Our entirely heterologous production system also establishes a basis for the future use of E. coli for generation of novel bioactive compounds through tolerable precursor-directed biosynthesis.