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

• Published in: Applied microbiology and biotechnology 2012-06, Vol.94 (6), p.1521-1532
• Main Authors: Jiang, Pei-xia, Wang, Hai-sheng, Xiao, Su, Fang, Ming-yue, Zhang, Rui-ping, He, Shu-ying, Lou, Kai, Xing, Xin-Hui
• Format: Article
• Language: English
• Subjects: Acids; Agronomy; Alkalis; Bacteria; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biological activity; Biomedical and Life Sciences; Biosynthesis; Biosynthetic Pathways; Biotechnological Products and Process Engineering; Biotechnology; Cell Line; Cell Proliferation - drug effects; Chemical properties; Chromosomes; Citrobacter freundii; Citrobacter freundii - genetics; Citrobacter freundii - metabolism; Gene expression; Genes; Humans; Indoles - chemistry; Indoles - metabolism; Indoles - pharmacology; Life Sciences; Metabolism; Metabolites; Microbial Genetics and Genomics; Microbiology; Molecular Structure; Multigene Family; Pigments, Biological - biosynthesis; Pigments, Biological - chemistry; Pigments, Biological - pharmacology; Polymerase chain reaction; Process engineering; Studies
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-012-3960-0

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.