Isolation, Characterization, and Antimicrobial Potential of Melanin from Fungi Associated with Marine Macroalgae

Background: The marine ecosystem provides an abundant array of distinctive enzymes and pigments. Macroalgae and their accompanying microorganisms are essential to the ecological and biochemical dynamics of coastal water. Method: The study entailed the collection of diverse macroalgae from three coastal sites in Egypt, from autumn 2022 to summer 2023. This study investigated the diversity of epiphytic fungi on marine macroalgae and their potential for melanin pigment production. Then melanin investigation was conducted using UV-visible and Fourier Transform Infrared (FTIR) spectroscopy. We subsequently explored the antimicrobial efficacy of melanin against various pathogenic microorganisms.". Results: - Seventeen fungal species from five genera were discovered. Aspergillus niger was the predominant species throughout all seasons, comprising 32.5% in winter, 39.4% in spring, and 37% in summer. In contrast, Cladosporium oxysporum , Trichoderma viride, and Curvularia chlamydospora were the least common. Ten identified epiphytic fungal species were observed to synthesize melanin pigment, including Aspergillus niger, A. flavus, A. terreus, A. fumigatus, Trichoderma viride, Cladosporium oxysporum , Curvularia chlamydospora, Alternaria alternata, Penicillium chrysogenum , and Rhizopus stolonifer. Subsequent investigations employing UV-visible spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy validated the identity of the pigments produced as melanin. The isolated melanin exhibited differing degrees of antimicrobial efficacy against various pathogenic bacteria and fungi, such as Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Salmonella typhi, and Candida albicans. Nevertheless, it demonstrated no efficacy against Aspergillus fumigatus. Conclusion: -The findings highlighted the potential of marine epiphytic fungi as a source of significant bioactive chemicals, especially melanin.