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

Xian Xu, Xiaoting Chu, Bangmian Du, Chunyan Huang, Chengjia Xie, Zhidong Zhang, Ling Jiang

Applied microbiology and biotechnology 2022 Apr

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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. © 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

Citation

Xian Xu, Xiaoting Chu, Bangmian Du, Chunyan Huang, Chengjia Xie, Zhidong Zhang, Ling Jiang. Functional characterization of a novel violacein biosynthesis operon from Janthinobacterium sp. B9-8. Applied microbiology and biotechnology. 2022 Apr;106(8):2903-2916