Work

Genetic, structural, and functional characterization of allomelanin from black yeast Exophiala viscosa, a chassis for fungal melanin production

Year: 2025

Type: article

Abstract: Melanized fungi are known for their remarkable resilience to environmental stress, largely attributed to the protective properties of melanin. In this study, we establish the black yeast Exophiala viscosa as a non-pathogenic, genetically tractable model for the scalable production and functional analysis of DHN-melanin (allomelanin). Cultivation in flasks and bioreactors yielded up to 8.6 g/L of melanin, with the majority tightly incorporated into the cell wall as "melanin ghosts". Chemical analyses including FTIR, XPS, ssNMR, and EPR confirmed the identity of the pigment as allomelanin and revealed a structural association with chitin. Gene deletions of Pks1, Arp2, and Abr2 validated the DHN-melanin biosynthetic pathway and enabled the generation of pigment-deficient mutants. Functional assays demonstrated that melanin contributes significantly to UV and cold tolerance, while offering limited protection against γ-radiation, suggesting that other pigments,such as carotenoids, may also play a protective role. The unique redox properties, structural integrity, and scalability of melanin production in E. viscosa highlight its potential for bio-derived materials used in radiation shielding, environmental remediation, and thermal regulation. This work establishes E. viscosa as a promising chassis for melanin biomanufacturing and a valuable model for studying fungal melanins in the context of materials science and environmental resilience. KEY POINTS: • Cultivation of E. viscosa in rich medium yielded up to 8.6 g/L of melanin. • Chemical and genetic analyses identified the pigment as allomelanin. • Melanin enhanced the tolerance of fungal cells to UV radiation and low temperatures.

Source: Applied Microbiology and Biotechnology

DOI: 10.1007/s00253-025-13597-w