AUTHOR=Koch Stella Marie , Freidank-Pohl Carsten , Siontas Oliver , Cortesao Marta , Mota Afonso , Runzheimer Katharina , Jung Sascha , Rebrosova Katarina , Siler Martin , Moeller Ralf , Meyer Vera 

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

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1233740

DOI=10.3389/fmicb.2023.1233740

ISSN=1664-302X

ABSTRACT=<p>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<sub>Fun</sub>) in <italic>A. niger</italic> by inducing overproduction of the pigment using L-tyrosine in a recombinant Δ<italic>hmgA</italic> mutant strain (OS4.3). The Pyo<sub>Fun</sub> 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<sub>Fun</sub> against non-ionizing radiation (monochromatic UV-C) and compared its efficacy to a synthetically produced control pyomelanin (Pyo<sub>Syn</sub>). The results confirmed successful production of Pyo<sub>Fun</sub> in <italic>A. niger</italic> through inducible overproduction. Characterization using spectroscopic methods confirmed the presence of Pyo<sub>Fun</sub>, and the DPPH-assay demonstrated its strong antioxidant properties. Moreover, Pyo<sub>Fun</sub> exhibited a highly protective effect against radiation-induced stress, surpassing the protection provided by Pyo<sub>Syn</sub>. The findings of this study suggest that Pyo<sub>Fun</sub> has significant potential as a biological shield against harmful radiation. Notably, Pyo<sub>Fun</sub> 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<sub>Fun</sub> 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.</p>