Metabolic Engineering of Microorganisms to Increase Production of Violacein

Violacein, an indole derivative, is a violent pigment which is extracted from the bacteria. It is considered to be an important aromatic compound as it exhibits essential antiparasitic, antimicrobial and antitumoral characteristics. One of the most eminent derivatives that is being induced by the biosynthetic pathway of violacein is deoxyviolacein. However, it is produced in an insignificant amount. By expunging the VioD protein from the violacein pathway, deoxyviolacein can be generated which is devoid of a hydroxyl group. Another derivative that was produced in addition to deoxyviolacein is oxyviolacein, generated by the derivative of tryptophan i.e. 5-hydroxytryptophan. In this review, our main focus is on different engineered microorganisms in increasing the production of the violacein. On undergoing genetic analysis and determining the basic mechanism of violacein production showed that, violacein is formed by the condensation of 2 tryptophan molecules in presence of vioABCD gene cluster. However, later on, the presence of another gene vioE was revealed to be involved in violacein biosynthesis and a new pathway was suggested. McClean reported the involvement of quorum sensing mechanism via AHL's in violacein biosynthesis. Then using the above information and using violacein gene cluster vioABCDE, the violacein was produced in C. violaceum, Pseudoalteromonas sp. 520P1, V. natriegens, C. glutamicum, E. coli, Y. lipolytica and D. violaceinigra. Then the amount of violacein was increased by subjecting it to either batch or fed-batch fermentation. Then after its production, its anti-microbial activity was determined against Staphylococcus species. Also, its anti-cancerous activity was also determined on resistant leukemia cells.