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 A. niger by inducing overproduction of the pigment using L-tyrosine in a recombinant Δ hmgA 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 A. niger 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.