Isolation and characterisation of melanin pigment from mycelial cultures of Xylaria polymorpha (Ascomycota)

Melanin is a heterogenic polymer of phenolic or indolic nature, possessing a broad spectrum of biological activities including radio- and photoprotective, antioxidant, chemoprotective, antiviral, antimicrobial, cytotoxic and immunostimulating activity. Based on these characteristics, natural melanin holds significant potential for applications in the fields of biomedicine, nanotechnology and materials science. Along with that, the exploration of organisms producing natural melanin remains relevant and filamentous fungi with their exceptional metabolic versatility are promising sources of these pigments. Wood-inhabiting fungi in particular are known to produce specific types of melanin as secondary metabolites. This study aimed to quantify and characterise melanin in the mycelium of various strains of Xylaria polymorpha, a common representative of wood-inhabiting fungi. As a result, among the ten studied strains of X. polymorpha, the highest melanin synthesis productivity was observed in the strain IBK 2737, reaching 180.32 ± 4.16 mg/l, while the lowest was recorded in the strain IBK 2723 at 5.17 ± 0.36 mg/l. This investigation highlights that X. polymorpha strains from the IBK Culture Collection show promise as a valuable source of natural melanin.