Iranian Journal of Medical Microbiology

Background and Aim: Melanin is a ubiquitous, dark, polymeric pigment found naturally in plants, animals and microbes. It has several industrial, biotechnological, and pharmaceutical applications. The study aimed to verify the presence, type, and quantity of melanin produced by eight species belonging to the Aspergillus (A.) section Nigri: A. awamori, A. brasiliensis, A. costaricaensis, A. luchuensis, A. piperis, A. niger, A. tubingensis and A. welwitschiae We also determined the biosynthetic pathway (either 3, 4-dihydroxyphenylalanine (DHN) or 1,8-dihydroxynaphthalene (DOPA)) responsible for melanin synthesis in these species.
Materials and Methods: Soil samples were collected from seven locations within Basrah Province. Species identification was performed through sequencing of ITS region and β-tubulin gene. The isolates were cultured on CDA and L-tyrosine PDA, and incubated for 7, 14 and 21 days for melanin extraction. Qualitative and quantitative characterizations of melanin were done using UV–Vis spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). The biosynthetic pathway of melanin was investigated by applying the pathway inhibitors; kojic acid and difenoconazole.
Results: The results indicated that A. niger produced 1.9 gr of melanin after 3 weeks on L-tyrosine PDA. DHN pathway was identified in A. niger and A. brasiliensis, whereas the DOPA pathway was active across all tested species.
Conclusion: The study revealed interspecies differences in the type and quantity of melanin produced among A. section Nigri isolates.