Analyzing the Effects of Monochromatic Lights on the Fungal Growth to Control the Progression of Microbial Deterioration on Animal Collections Preserved in the Zoological Museum of Naples, Italy

Exposing artworks and artifacts in museums is fundamental to disseminate culture and knowledge but is also risky since the exposure to environmental conditions can deteriorate exhibited objects. Light is crucial, being able to trigger photochemical effects, and jointly responsible (with temperature and humidity) for biological risk generation. In this context, fungal growth in museum artifacts is a damaging factor that should not be underestimated. Consequently, the study of lighting effects on fungi development is essential. In this work, five different fungal strains (Aspergillus fumigatus, Bjerkandera adusta, Fusarium oxysporum, Penicillium chrysogenum, and Penicillium granulatum) isolated from samplings on animal exhibits hosted in the Zoological Museum of Naples, Italy, are cultivated inside four experimental boxes, equipped with monochromatic LEDs with different peak wavelengths (460 nm, 518 nm, 594 nm, and 638 nm). The growth rate, the protein and carbohydrate contents are analyzed and compared to results obtained in darkness (typical growth conditions for studies about fungi). Results demonstrate that, even if fungi are heterotrophic organisms and do not need light to grow and develop, their growth rate, and their protein and carbohydrate contents are affected by the exposure to monochromatic radiation, but the spectral sensitivity strictly depends on the analyzed species. For this reason, it is not possible to infer general practical guidelines for lighting applications, and it becomes urgent to establish accurate and shared analysis protocols to be applied case by case, to study the effects of the environmental conditions on microorganisms and drive-specific design choices.