Synthetic Consolidants Attacked by Melanin-Producing Fungi: Case Study of the Biodeterioration of Milan (Italy) Cathedral Marble Treated with Acrylics

Abstract

Monuments and artistic stone surfaces are often consolidated and protected with synthetic polymers, in particular, acrylics. Although it is generally thought that acrylic polymers are resistant to biodeterioration, we report for the first time the systematic occurrence of dematiaceous meristematic fungi on many marble samples of the cathedral in Milan (Italy) previously treated with this material. Fourier transform infrared spectroscopy applied to the Milan cathedral stone samples revealed characteristic features of biodeteriorated synthetic resins that differentiated them from the aged but nonbiodeteriorated samples. Samples showing biological colonization were analyzed for the presence of fungi. Cultivation and morphological characterization and methods independent from cultivation, such as denaturing gradient gel electrophoresis coupled with partial 18S rRNA gene sequencing and immunofluorescence staining with melanin-binding antibodies, showed that melanin-producing species are heavily present on stone surfaces protected with acrylic resins. This observation raises the question of the effectiveness of acrylics in protecting stone artworks.

The assessment of fungal bioaerosols in the crypt of St. Peter in Perugia (Italy)

“…Fungal organisms, for the large capacity of metabolic adaptation, can colonize and use as a nutritional substrate also synthetic polymers (Lugauskas et al, 2003). In presence of some polymers in which the organic fraction is absent the fungi development is linked to the organic additives present in the silicone resin used to protect and consolidate stone materials (Cappitelli et al, 2007). Therefore, the aim of this study was to investigate, through different methodologies, the presence of airborne microrganisms, potentially biodeteriogens for the stone artefacts in a semiunderground environment.…”

Microorganisms Attack Synthetic Polymers in Items Representing Our Cultural Heritage

“…In addition, the fungal presence and spatial distribution were evaluated using immunofluorescence staining with melanin-binding antibodies. In contrast, freshly dried polyisobutylmethacrylate subjected to biodeterioration treatment showed only light fungal growth (9). The chemical and physical degradation of the polymer was in turn likely to have facilitated biological degradation (10).…”

“…A technique such as infrared spectroscopy offers the opportunity to monitor real-time chemical changes (55). Importantly, biodeteriorated synthetic resins used in conservation have recently been distinguished from the same nonbiodeteriorated polymers by the presence of a peptidic bond in the infrared spectrum (8,9,14).…”

Weathering patinas on the medieval (S. XIV) stained glass windows of the Pedralbes Monastery (Barcelona, Spain)

“…However, this calcite presents There is probably some overlapping between calcite and Ca-oxalate bands, for example on the double peak at 874 and 780 cm −1 . The peak at 1,730 cm −1 can be related to carbonyl stretching (Cappitelli et al 2007). The quartz bands (1,200, 1,150, 1,030, 799, 512, and 469 cm −1 ) are all in good agreement with quartz absorbances displayed by other authors (e.g., Etchepare et al 1974;Williams 1995. The XRD and FTIR spectra evidenced certain specific characteristics and associations between the neoformed mineral phases.…”