A comparative study of the fungal flora present in medieval wall paintings in the chapel of the castle Herberstein and in the parish church of St Georgen in Styria, Austria

Fungi were isolated from selected areas of two medieval wall paintings in the chapel of the castle of Herberstein and the parish church of St Georgen (Styria, Austria), in different states of conservation. The aim of this study is a contribution to the knowledge of mycoflora that occurs on frescoes. The fungal colonies were characterized using a chemotaxonomical approach based on the analysis of ubiquinone systems, comparison of protein patterns and classical morphological methods following identification keys. The results show that the mycoflora can vary from each sampling site even when the environmental conditions are similar. The majority of fungal colonies were isolated from the paintings in Herberstein. Since the last restoration of the paintings in 1950, the chapel of Herberstein has been neglected and the walls have been significantly affected by the accumulation of moisture. In St Georgen, prolonged dampness and salts were responsible for the main damage to the paintings. Fungi were mainly found to grow on the remaining fibers of the cellulose pulp used during restoration. Twenty different fungal forms were isolated, the most common belonging to the genera Acremonium, Engyodontium, Cladosporium, Blastobotrys, Verticillium Mortierella, Aspergillus and Penicillium. Some of them are known to occur on frescoes, but a few species have not been isolated before on this substrate. An inventory of fungi isolated in Herberstein and St Georgen was undertaken to give measures for restoration in order to prevent further damage.