Aspergillus niger as a cell factory for the production of pyomelanin, a molecule with UV-C radiation shielding activity

Abstract

Melanins are complex pigments with various biological functions and potential applications in space exploration and biomedicine due to their radioprotective properties. Aspergillus niger, a fungus known for its high radiation resistance, is widely used in biotechnology and a candidate for melanin production. In this study, we investigated the production of fungal pyomelanin (Pyo_Fun) in <i>A. niger</i> by inducing overproduction of the pigment using L-tyrosine in a recombinant Δ<i>hmgA</i> mutant strain (OS4.3). The Pyo_Fun pigment was characterized using three spectroscopic methods, and its antioxidant properties were assessed using a DPPH-assay. Additionally, we evaluated the protective effect of Pyo_Fun against non-ionizing radiation (monochromatic UV-C) and compared its efficacy to a synthetically produced control pyomelanin (Pyo_Syn). The results confirmed successful production of Pyo_Fun in <i>A. niger</i> through inducible overproduction. Characterization using spectroscopic methods confirmed the presence of Pyo_Fun, and the DPPH-assay demonstrated its strong antioxidant properties. Moreover, Pyo_Fun exhibited a highly protective effect against radiation-induced stress, surpassing the protection provided by Pyo_Syn. The findings of this study suggest that Pyo_Fun has significant potential as a biological shield against harmful radiation. Notably, Pyo_Fun is synthesized extracellularly, differing it from other fungal melanins (such as L-DOPA- or DHN-melanin) that require cell lysis for pigment purification. This characteristic makes Pyo_Fun a valuable resource for biotechnology, biomedicine, and the space industry. However, further research is needed to evaluate its protective effect in a dried form and against ionizing radiation.