Melanin production and biosynthetic pathways in Aspergillus section Nigri species cultured in liquid media

Abstract

As a result of being cost-friendly, consuming fewer chemicals and enabling simple purification, means for preparing the natural pigment melanin have become a dominant avenue. This study aimed to characterise and determine the amount and type of biosynthesis of fungal melanin from 8 species of Aspergillus section Nigri cultured in two liquid culture media, including potato dextrose broth (PDB) and L-tyrosine PDB, for 21 days. Aspergillus section Nigri species were identified by using Internal Transcribed Spacer (ITS), β-tubulin (BenA) and calmodulin (CaM). Qualitative and quantitative analyses of melanin using ultraviolet-visible analysis, Fourier transformed infrared (FTIR) analysis, scanning electron microscopy and atomic force microscopy. The results showed that the extracted melanin amount in powder form them were ranged from (0.3-2 g) at the end of incubation in culture media. The concentration of melanin extracted from species cultured in PDB was ranged from (37.40-134.28 ppm) while in L-tyrosine PDB liquid media, the findings indicate that the concentration range was (53.03-140.53ppm). Two inhibitors were used to determine the biosynthetic pathway, difenoconazole used for the first time, and kojic acid. l-3,4-dihydroxyphenylalanine was the pathway for melanin synthesis in A. niger and A. brasiliensis, and all the investigated species commonly produced melanin through the DHN pathway.