Systems metabolic engineering of Escherichia coli for production of violacein and deoxyviolacein

Violacein and deoxyviolacein are promising therapeutics against pathogenic bacteria and viruses as well as tumor cells. In the present work, systems-wide metabolic engineering was applied to Escherichia coli for heterologous production of these high-value products. First, a high performance liquid chromatography method for accurate separation and quantification of violacein and deoxyviolacein was developed. Afterwards, a basic producer, E. coli dVio-1, that expressed the vioABCE cluster from Chromobacterium violaceum under control of the araBAD promoter and induction by L-arabinose, was constructed. Targeted intracellular metabolite analysis then identified bottlenecks in pathways that supply tryptophan, the major product building block of the natural products of interest. This was used for systems-wide engineering of serine, chorismate and tryptophan biosynthesis and the non-oxidative pentose-phosphate pathway, followed by elimination of L-arabinose catabolism. Transferred to a glycerol-based fed-batch process, E. coli dVio-8 surpassed the gram scale and produced 1.6 g L-1 deoxyviolacein (> 99.5% purity). The created chassis of a high-flux tryptophan pathway was complemented by genomic integration of the vioD gene of Janthinobacterium lividum, which enabled exclusive production of violacein (710 mg L-1 with 99.8% purity). This demonstrates the potential of E. coli as a platform for production of tryptophan based therapeutics.