Study of the properties of carotenoids and key carotenoid biosynthesis genes from Deinococcus xibeiensis R13

Recent Advances on Key Enzymes of Microbial Origin in the Lycopene Biosynthesis Pathway

Lycopene is a common carotenoid found mainly in ripe red fruits and vegetables that is widely used in the food industry due to its characteristic color and health benefits. Microbial synthesis of lycopene is gradually replacing the traditional methods of plant extraction and chemical synthesis as a more economical and productive manufacturing strategy. The biosynthesis of lycopene is a typical multienzyme cascade reaction, and it is important to understand the characteristics of each key enzyme involved and how they are regulated. In this paper, the catalytic characteristics of the key enzymes involved in the lycopene biosynthesis pathway and related studies are first discussed in detail. Then, the strategies applied to the key enzymes of lycopene synthesis, including fusion proteins, enzyme screening, combinatorial engineering, CRISPR/Cas9-based gene editing, DNA assembly, and scaffolding technologies are purposefully illustrated and compared in terms of both traditional and emerging multienzyme regulatory strategies. Finally, future developments and regulatory options for multienzyme synthesis of lycopene and similar secondary metabolites are also discussed.

Research progress of engineering microbial cell factories for pigment production

Pigments are widely used in people's daily life, such as food additives, cosmetics, pharmaceuticals, textiles, etc. In recent years, the natural pigments produced by microorganisms have attracted increased attention because these processes cannot be affected by seasons like the plant extraction methods, and can also avoid the environmental pollution problems caused by chemical synthesis. Synthetic biology and metabolic engineering have been used to construct and optimize metabolic pathways for production of natural pigments in cellular factories. Building microbial cell factories for synthesis of natural pigments has many advantages, including well-defined genetic background of the strains, high-density and rapid culture of cells, etc. Until now, the technical means about engineering microbial cell factories for pigment production and metabolic regulation processes have not been systematically analyzed and summarized. Therefore, the studies about construction, modification and regulation of synthetic pathways for microbial synthesis of pigments in recent years have been reviewed, aiming to provide an up-to-date summary of engineering strategies for microbial synthesis of natural pigments including carotenoids, melanins, riboflavins, azomycetes and quinones. This review should provide new ideas for further improving microbial production of natural pigments in the future.

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

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.