Characterization of melanin pigment from Aspergillus terreus LCM8 and its role in cadmium remediation

Considering the persistent nature and impending health threats of potentially toxic metals, it is essential to reduce its environmental burden via novel techniques with respect to eco-friendliness, efficiency, and low operational cost. In this study, filamentous fungus designated as strain LCM8, producing dark brown pigment under the cadmium stress, was isolated from the metal-polluted riverbank soil. The fungus was identified as Aspergillus terreus based on ITS sequencing and evaluated for optimized growth conditions and cadmium tolerance. The strain was then subjected to pigment production under optimized growth conditions followed by its extraction and characterization through chemical tests, UV–visible analysis, glutathione inhibitor, and FTIR spectroscopy in parallel to synthetic melanin as control. Further, the pigment was assessed for its metal chelation ability and cadmium removal via atomic absorption spectrometry, FTIR, and SEM–EDX analyses. Aspergillus terreus LCM8 can tolerate cadmium up to 2000 mg/L and yielded 300 mg/L pigment in 15 days. Preliminary analyses suggested the obtained pigment as melanin. The biosynthetic melanin reduced cadmium up to 40 ± 1% in an aqueous solution with initial concentration of 100 mg/L in 7 days. The demonstration of cadmium removal by fungal melanin advocates its potential applicability in cadmium remediation strategies that are essential for environmental safety and public health.