Functional characterization of a novel violacein biosynthesis operon from Janthinobacterium sp. B9-8

• Published in: Applied microbiology and biotechnology 2022-04, Vol.106 (8), p.2903-2916
• Main Authors: Xu, Xian, Chu, Xiaoting, Du, Bangmian, Huang, Chunyan, Xie, Chengjia, Zhang, Zhidong, Jiang, Ling
• Format: Article
• Language: English
• Subjects: Anticancer properties; Bacteria; Biomedical and Life Sciences; Biosynthesis; Biotechnological Products and Process Engineering; Biotechnology; E coli; Escherichia coli; Escherichia coli - genetics; Escherichia coli - metabolism; Fermentation; Genomes; Gram-negative bacteria; Indoles - metabolism; Inoculum; Life Sciences; Metabolites; Microbial Genetics and Genomics; Microbiology; Microorganisms; Natural products; Operon; Oxalobacteraceae - genetics; Physiological aspects; Plasmids; Proteobacteria; Tryptophan; Tumors; Violacein
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-022-11929-8

Violacein is a secondary metabolite mainly produced by Gram-negative bacteria that is formed from tryptophan by five enzymes encoded by a single operon. It is a broad-spectrum antibacterial pigment with various important biological activities such as anti-tumor, antiviral, and antioxidative effects. The newly discovered violacein operon vioABCDE was identified in the genome of the extremophile Janthinobacterium sp. B9-8. The key enzyme-encoding genes were cloned to construct the multigene coexpression plasmids pET-vioAB and pRSF-vioCDE. The violacein biosynthesis pathway was heterologously introduced into engineered Escherichia coli VioABCDE and VioABCDE-SD. The factors affecting violacein production, including temperature, pH, inoculum size, carbon and nitrogen source, precursor, and inducers were investigated. The violacein titer of VioABCDE-SD reached 107 mg/L in a two-stage fermentation process, representing a 454.4% increase over the original strain. The violacein operon from B9-8 provides a new microbial gene source for the analysis of the violacein synthesis mechanism, and the constructed engineering E. coli strains lay a foundation for the efficient and rapid synthesis of other natural products. Key points • The newly discovered violacein operon vioABCDE was identified in the genome of the extremophile Janthinobacterium sp. B9-8. • The violacein synthesis pathway was reconstructed in E. coli using two compatible plasmids. • A two-stage fermentation process was optimized for improved violacein accumulation.