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owth of xerophilic fungi on model paint samples on glass and wooden
supports under low humidity conditions
Janez Kosel 1, Jakub Sandak 2,3, Anna Sandak 2,4, Lea Legan 1, Klara Retko 1, Maša Kavčič 1,
Črtomir Tavzes 1, Miklos Krész 2,3, Polonca Ropret 1
1. Institute for the Protection of Cultural Heritage of Slovenia, Conservation Centre, Research Institute, SI-1000 Ljubljana, Slovenia,
janez.kosel@zvkds.si
2. InnoRenew CoE, Livade 6, 6310 Izola
3. Andrej Marušič Institute, Muzejski trg 2, University of Primorska, 6000 Koper, Slovenia
4. Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska, Glagoljaška 8, 6000 Koper,
Slovenia
In museums, xerophilic fungi can grow and thrive on a wide range of art objects. Their dispersion is affected
by the regular movement of museum staff and visitors, and by the ventilation system. Many works of art,
such as panel paintings and polychromed wooden sculptures, are composed of an array of different
organic substances, including traditional cellulose-based support materials, protein-, lipid-based and
other types of adhesives, binders, coatings, and colouring agents, which all represent nutrient-rich media
prone to colonization by xerophilic fungi (Grabek-Lejko et al., 2017). In contrast, the presence of metal ions
(e.g., lead, zinc, chromium, etc.) in some pigments’ chemical composition can increase the resistance of
a paint layer to biodeterioration. Surprisingly, the xerophilic potential of fungi isolated from museums’
indoor environments has never been addressed properly. To assess this fungal trait, most studies only
use simple selective solid media with high concentrations of sodium chloride or glucose, which lower
the water activity of a medium (Koutsoumanis and Sofos, 2005). Therefore, our aim was to carefully
investigate 11 fungal strains isolated from cultural heritage institutions’ interiors for their potential to grow
on painted heritage items at low relative humidity (xerophilic potential). The isolates were inoculated
onto model samples made of wooden and glass supports coated with a layer of egg tempera paint.
Different paints, prepared with egg binder and assorted traditional artists’ pigments (lead white, Prussian
blue, carmine lake and verdigris) were investigated. Model samples were subjected to 50, 60 and 70 %
relative humidity. Fungal development was carefully monitored by fluorescent microscopy. Our results
show that relative humidity of 50 or 60 % can still support mould growth and biodeterioration (incubation
of 3 months), especially in the case of paints on wooden supports containing Prussian blue pigment.
Indeed, wood, by absorbing moisture (hygroscopic material), enables the development of favourable
microclimatic conditions for mould growth.
Keywords: Aspergillus, Penicillium, xerophilic fungi, pigments
Acknowledgement
The authors gratefully acknowledge receiving funding from the InnoRenew project under the Horizon2020
Widespread-2-Teaming program (grant agreement ID: 739574; start-up project 6.1. Advanced materials
for cultural heritage storage). Authors from the Institute for the Protection of Cultural Heritage of Slovenia
also acknowledge funding from the Slovenian Research Agency (grants J7-1815 and BI-RS/20-21-013).
References
Grabek-Lejko, D., Tekiela, A., Kasprzyk, I., 2017. Risk of biodeterioration of cultural heritage objects, stored in the
historical and modern repositories in the Regional Museum in Rzeszow (Poland). A case study. Int. Biodeterior.
Biodegrad. 123, 46–55. https://doi.org/10.1016/j.ibiod.2017.05.028
Koutsoumanis, K.P., Sofos,J.N., 2005. Effect of inoculum size on the combined temperature, pH and awlimits forgrowth
of Listeria monocytogenes. Int. J. Food Microbiol. 104, 83–91. https://doi.org/10.1016/j.ijfoodmicro.2005.01.010
Poyatos, F., Morales, F., Nicholson, A.W., Giordano, A., 2018. Physiology of biodeterioration on canvas paintings. J.
Cell. Physiol. https://doi.org/10.1002/jcp.26088
INNORENEW COE INTERNATIONAL CONFERENCE 2021
16
supports under low humidity conditions
Janez Kosel 1, Jakub Sandak 2,3, Anna Sandak 2,4, Lea Legan 1, Klara Retko 1, Maša Kavčič 1,
Črtomir Tavzes 1, Miklos Krész 2,3, Polonca Ropret 1
1. Institute for the Protection of Cultural Heritage of Slovenia, Conservation Centre, Research Institute, SI-1000 Ljubljana, Slovenia,
janez.kosel@zvkds.si
2. InnoRenew CoE, Livade 6, 6310 Izola
3. Andrej Marušič Institute, Muzejski trg 2, University of Primorska, 6000 Koper, Slovenia
4. Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska, Glagoljaška 8, 6000 Koper,
Slovenia
In museums, xerophilic fungi can grow and thrive on a wide range of art objects. Their dispersion is affected
by the regular movement of museum staff and visitors, and by the ventilation system. Many works of art,
such as panel paintings and polychromed wooden sculptures, are composed of an array of different
organic substances, including traditional cellulose-based support materials, protein-, lipid-based and
other types of adhesives, binders, coatings, and colouring agents, which all represent nutrient-rich media
prone to colonization by xerophilic fungi (Grabek-Lejko et al., 2017). In contrast, the presence of metal ions
(e.g., lead, zinc, chromium, etc.) in some pigments’ chemical composition can increase the resistance of
a paint layer to biodeterioration. Surprisingly, the xerophilic potential of fungi isolated from museums’
indoor environments has never been addressed properly. To assess this fungal trait, most studies only
use simple selective solid media with high concentrations of sodium chloride or glucose, which lower
the water activity of a medium (Koutsoumanis and Sofos, 2005). Therefore, our aim was to carefully
investigate 11 fungal strains isolated from cultural heritage institutions’ interiors for their potential to grow
on painted heritage items at low relative humidity (xerophilic potential). The isolates were inoculated
onto model samples made of wooden and glass supports coated with a layer of egg tempera paint.
Different paints, prepared with egg binder and assorted traditional artists’ pigments (lead white, Prussian
blue, carmine lake and verdigris) were investigated. Model samples were subjected to 50, 60 and 70 %
relative humidity. Fungal development was carefully monitored by fluorescent microscopy. Our results
show that relative humidity of 50 or 60 % can still support mould growth and biodeterioration (incubation
of 3 months), especially in the case of paints on wooden supports containing Prussian blue pigment.
Indeed, wood, by absorbing moisture (hygroscopic material), enables the development of favourable
microclimatic conditions for mould growth.
Keywords: Aspergillus, Penicillium, xerophilic fungi, pigments
Acknowledgement
The authors gratefully acknowledge receiving funding from the InnoRenew project under the Horizon2020
Widespread-2-Teaming program (grant agreement ID: 739574; start-up project 6.1. Advanced materials
for cultural heritage storage). Authors from the Institute for the Protection of Cultural Heritage of Slovenia
also acknowledge funding from the Slovenian Research Agency (grants J7-1815 and BI-RS/20-21-013).
References
Grabek-Lejko, D., Tekiela, A., Kasprzyk, I., 2017. Risk of biodeterioration of cultural heritage objects, stored in the
historical and modern repositories in the Regional Museum in Rzeszow (Poland). A case study. Int. Biodeterior.
Biodegrad. 123, 46–55. https://doi.org/10.1016/j.ibiod.2017.05.028
Koutsoumanis, K.P., Sofos,J.N., 2005. Effect of inoculum size on the combined temperature, pH and awlimits forgrowth
of Listeria monocytogenes. Int. J. Food Microbiol. 104, 83–91. https://doi.org/10.1016/j.ijfoodmicro.2005.01.010
Poyatos, F., Morales, F., Nicholson, A.W., Giordano, A., 2018. Physiology of biodeterioration on canvas paintings. J.
Cell. Physiol. https://doi.org/10.1002/jcp.26088
INNORENEW COE INTERNATIONAL CONFERENCE 2021
16
