Pathway redesign for deoxyviolacein biosynthesis in Citrobacter freundii and characterization of this pigment

Abstract

Violacein (Vio) is an important purple pigment with many potential bioactivities. Deoxyviolacein, a structural analog of Vio, is always synthesized in low concentrations with Vio in wild-type bacteria. Due to deoxyviolacein's low production and difficulties in isolation and purification, little has been learned regarding its function and potential applications. This study was the first effort in developing a stable and efficient biosynthetic system for producing pure deoxyviolacein. A recombinant plasmid with vioabce genes was constructed by splicing using an overlapping extension-polymerase chain reaction, based on the Vio-synthesizing gene cluster of vioabcde, originating from Duganella sp. B2, and was introduced into Citrobacter freundii. With the viod gene disrupted in the Vio synthetic pathway, Vio production was completely abolished and the recombinant C. freundii synthesized only deoxyviolacein. Interestingly, vioe gene expression was strongly stimulated in the viod-deleted recombinant strain, indicating that viod disruptions could potentially induce polar effects upon the downstream vioe gene within this small operon. Deoxyviolacein production by this strain reached 1.9 g/L in shaker flasks. The product exhibited significant acid/alkali and UV resistance as well as significant inhibition of hepatocellular carcinoma cell proliferation at low concentrations of 0.1-1 μM. These physical characteristics and antitumor activities of deoxyviolacein contribute to illuminating its potential applications.

Optoregulated Drug Release from an Engineered Living Hydrogel

“…10 Among these, the L-tryptophan-derived bisindoles, i.e. deoxyviolacein and the structurally analogous violacein, are attractive due to their antibacterial, 36,37 antifungal, 38 and anti-tumoral properties 37,39 and the possibility to produce them at gram scales with E. coli. 34,35 Numerous available genetic modules allow it to respond E coli.…”

Systems metabolic engineering of Escherichia coli for gram scale production of the antitumor drug deoxyviolacein from glycerol

“…Deoxyviolacein is a microbial metabolite that receives high interest due to its biological activity against tumors (Jiang et al, ), gram‐positive bacteria, and plant pathogenic fungi (Wang et al, ). Biosynthesis of this compound occurs naturally in different bacteria and involves a series of biochemical reactions that start from the precursor L ‐tryptophan and proceed through a cascade of enzymes encoded by the vioABCE operon (Hoshino, ).…”

Optoregulated Drug Release from an Engineered Living Material: Self‐Replenishing Drug Depots for Long‐Term, Light‐Regulated Delivery

“…E. coli has been engineered for metabolic production of drugs such as artemisinin, cinnamaldehyde, carbapenem, violacein, deoxyviolacein (dVio), etc., at industrial scales . Among these, the l ‐tryptophan‐derived bisindoles dVio and violacein are attractive due to their antibacterial, antifungal, and antitumoral properties and the possibility to produce them at gram scales . dVio is synthesized from endogenously produced l ‐tryptophan by expressing four enzymes, vioA, vioB, vioC, and vioE, in E. coli , genetically encoded as a vioABCE operon .…”

“…During our initial experiments of dVio synthesis in liquid cultures, we observed that the drug remained within the bacteria and barely diffused to the surrounding medium (Figure S3, Supporting Information). This was attributed to dVio's poor water solubility, causing its aggregation in the bacterial cytosol. Solubilization and release of dVio from the bacteria was achieved by adding the nonionic surfactant Genapol C200 (Gen) to the medium.…”