Degradation Potential of Xerophilic and Xerotolerant Fungi Contaminating Historic Canvas Paintings

Abstract

Fungi are important contaminants of historic canvas paintings worldwide. They can grow on both sides of the canvas and decompose various components of the paintings. They excrete pigments and acids that change the visual appearance of the paintings and weaken their structure, leading to flaking and cracking. With the aim of recognizing the most dangerous fungal species to the integrity and stability of paintings, we studied 55 recently isolated and identified strains from historic paintings or depositories, including 46 species from 16 genera. The fungi were categorized as xero/halotolerant or xero/halophilic based on their preference for solutes (glycerol or NaCl) that lower the water activity (aw) of the medium. Accordingly, the aw value of all further test media had to be adjusted to allow the growth of xero/halophilic species. The isolates were tested for growth at 15, 24 °C and 37 °C. The biodeterioration potential of the fungi was evaluated by screening their acidification properties, their ability to excrete pigments and their enzymatic activities, which were selected based on the available nutrients in paintings on canvas. A DNase test was performed to determine whether the selected fungi could utilize DNA of dead microbial cells that may be covering surfaces of the painting. The sequestration of Fe, which is made available through the production of siderophores, was also tested. The ability to degrade aromatic and aliphatic substrates was investigated to consider the potential degradation of synthetic restoration materials. Xerotolerant and moderately xerophilic species showed a broader spectrum of enzymatic activities than obligate xerophilic species: urease, β-glucosidase, and esterase predominated, while obligate xerophiles mostly exhibited β-glucosidase, DNase, and urease activity. Xerotolerant and moderately xerophilic species with the highest degradation potential belong to the genus Penicillium, while Aspergillus penicillioides and A. salinicola represent obligately xerophilic species with the most diverse degradation potential in low aw environments.

Once upon a Time, There Was a Piece of Wood: Present Knowledge and Future Perspectives in Fungal Deterioration of Wooden Cultural Heritage in Terrestrial Ecosystems and Diagnostic Tools

“…In light of the occurring climatic changes, more preventive shared protocols and warning limits are needed. [84,195,206] Cellulase NaNO 3 2 g KH 2 PO 4 1 g MgSO 4 •7H 2 O 0.5 g KCl 0.5 g FeSO 4 0.01 g agar, 20 g crystalline cellulose 10 g pH 5.5 - [203] Cellulase Yeast Nitrogen Base 6.7 g glucose 1 g cellulose 5 g 0.3 g/L Congo Red solution [192] Endoglucanase Peptone Yeast extract agar supplemented of azurine cross-linked hydroxyethyl-cellulose (AZCL-HE-Cellulose) 0.5 g [197] Table A1 (15 min) destain [193] b-glucosidase Cz agar with aesculin 3 g - [211] b-glucosidase YNB 6.7 g agar 20 g; arbutin (hydroquinone b-D-glucopyranoside) 4 g pH 5.0 [197] Laccase Cz Dox Agar with guaiacol 0.05% (w/v) [199] Laccase PDA with guaiacol (0.02% v/v) [201] Laccase NA with 0.01% guaiacol [198] Laccase PDA with guaiacol 0.04% (v/v) [200] Laccase Glucose 2 g peptone 1 g yeast extract 0.1 g agar 16 g Remazol Brilliant Blue R 0.4 g [75,102] Lignin peroxidase Cz agar with azure B 0.0025% (w/v) [199] Lignin peroxidase Glucose 2 g peptone 1 g yeast extract 0. Mn peroxidase Cz agar with 0.0025% Phenol Red (w/v) [199] Mn peroxidase Glucose 2 g peptone 1 g yeast extract 0.1 g agar 16 g Phenol Red 0.1 g [75,102] Table A1.…”

Deterioration-associated microbiome of a modern photographic artwork: the case of Skull and Crossbones by Robert Mapplethorpe

“…To date, only a few studies have considered the features and mechanisms of biological degradation of photographic artworks, as further discussed below in this work. Additionally, it is worth noting that until now, the few published works on photographic artworks have focused either solely on microbial characterization or solely on their chemical degradation, without simultaneously considering both aspects [17][18][19][20][21][22]. The combined approach used in this study paves the way for a far-sighted non-invasive methodology to study modern non-conventional artworks, such as photographs.…”