Characterization and application of melanin produced by the fast-growing marine bacterium through heterologous biosynthesis.

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TitleCharacterization and application of melanin produced by the fast-growing marine bacterium through heterologous biosynthesis.
Publication TypeJournal Article
Year of Publication2019
AuthorsWang, Z, Tschirhart, T, Schultzhaus, Z, Kelly, EE, Chen, A, Oh, E, Nag, O, Glaser, ER, Kim, E, Lloyd, PF, Charles, PT, Li, W, Leary, D, Compton, J, Phillips, DA, Dhinojwala, A, Payne, GF, Vora, GJ
JournalAppl Environ Microbiol
Date Published2019 Dec 13

Melanin is a pigment produced by organisms throughout all domains of life. Due to its unique physicochemical properties, biocompatibility and biostability, there has been an increasing interest in the use of melanin for broad applications. In the vast majority of studies, melanin has been either chemically synthesized or isolated from animals, which has restricted its use to small-scale applications. Using bacteria as biocatalysts is a promising and economical alternative for the large-scale production of biomaterials. In this study, we engineered the marine bacterium one of the fastest growing organisms, to synthesize melanin by expressing a heterologous tyrosinase gene and demonstrated that melanin production was much faster than in previously reported heterologous systems. melanin was characterized as a polymer derived from dihydroxyindole-2-carboxylic acid (DHICA) and, similarly to synthetic melanin, exhibited several characteristic and useful features.Electron microscopy analysis demonstrated that melanin produced from nanoparticles that were assembled as 'melanin ghost' structures, and the photoprotective properties of these particles were validated by their protection of cells from UV irradiation. Using a novel electrochemical reverse engineering method, we observed that melanization conferred redox activities to Moreover, melanized bacteria were able to quickly adsorb organic compound trinitrotoluene (TNT). Overall, the genetic tractability, rapid division time, and ease of culture provide a set of attractive properties that compare favorably to current production strains and warrant the further development of this chassis as a microbial factory for natural product biosynthesis. Melanins are macromolecules that are ubiquitous in nature and impart a large variety of biological functions including structure, coloration, radiation resistance, free radical scavenging, and thermoregulation. Currently, in the majority of investigations, melanins are either chemically synthesized or extracted from animals, which presents significant challenges for large scale production. Bacteria have been used as biocatalysts to synthesize a variety of biomaterials due to their fast growth and amenability to genetic engineering using synthetic biology tools. In this study, we engineered the extremely fast-growing bacterium to synthesize melanin nanoparticles by expressing a heterologous tyrosinase gene with inducible promoters. Characterization of the melanin produced from -produced tyrosinase revealed that it exhibited similar physical and chemical properties to natural and chemically synthesized melanins, including nanoparticle structure, protection against UV damage, and adsorption of toxic compounds. We anticipate that producing and controlling melanin structures at the nanoscale in this bacterial system with synthetic biology tools will enable the design and rapid production of novel biomaterials for multiple applications.

Alternate JournalAppl. Environ. Microbiol.
PubMed ID31836580