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- Enzymatic degradation of fungal pigmentation from Wall painting’s isolatesPublication . Marco, A.; Moreira, P. R.; Pintado, M. E.; Vieira, EduardaEnzymatic discolouration of extracellular pigments produced in liquid media by a selected fungal isolate from Portuguese mural paintings was attempted both in solution and on solid support. A promising versatile peroxidase from Bjerkandera adusta was tested and presented interesting discolouration ability, although smaller than the values obtained with the use of hydrogen peroxide alone.
- Basil essential oil as an alternative to commercial biocides against fungi associated with black stains in mural paintingPublication . Marco, Alexandra; Santos, Sandra; Caetano, Joaquim; Pintado, Manuela; Vieira, Eduarda; Moreira, Patrícia R.In northern Portugal it was identified that some mural paintings from the 15th and 16th centuries disclose a chromatic alteration in the form of black stains possibly of microbiological origin. In the search for its cause, samples were collected and microorganisms were isolated from selected areas of the pictorial sets of three case studies that displayed dark pigmentation. Four representative fungal isolates were selected due to their pigmentation and growth characteristics – Alternaria alternata, Alternaria tenuissima, TZ10.2.2 (possibly Pestaloptia sp.) and TZ8.2.2 (possibly Penicillium sp.). An attempt was made to encounter an innovative environmentally innocuous and green safe alternative biocide to replace the chemical-based toxic compounds currently in use. Essential oils with confirmed antifungal potential and seldom employed in the conservation of cultural heritage and even less in mural painting (Rosmarinus officinalis, Foeniculum vulgare, Citrus lemmon, Ocimum basilicum and Salvia officinalis), were tested against commercial biocides (Benzalkonium chloride, Preventol R80, CaSoPaL® and Durolith®), to evaluate their in vitro efficacy and the determination of the minimum inhibitory concentration. Basil was able to inhibit growth on all tested strains at 1.25 μl ml−1. From the commercial biocides, Benzalkonium chloride and Preventol R80 were the ones with the best performance but needed higher concentrations than basil to achieve the same result enabling this essential oil a useful alternative to commercial biocides. The literature regarding the use of essential oils in mural paintings is, apart from two known authors, practically non-existent making it a novel approach.
- Rare biogeochemical phenomenon associated to manganese patinas on mural painting and granite ashlarsPublication . Campos, Bruno; Marco, Alexandra; Freire-Lista, David M.; Durães, Nuno; Silvestre-Albero, Joaquin; Silva, Eduardo Ferreira da; Vieira, Eduarda; Pintado, Manuela; Moreira, Patrícia R.This article discloses a rare and outstanding type of Mn-rich black-blue patina found on mural painting and granite ashlars located in the church of Sta. Marinha, north of Portugal, and conjectures the phenomenon associated to the appearance of such patinas in different surface materials. This Mn-patina reported on mural painting and their origin is probably assigned to manganese leaching from building materials (i.e., granite and phyllites). Stained mural painting and granite examined by XPS and SEM have showed patinas enriched with manganese (IV) oxide, potentially catalysed by a microbiota, like fungi, observed in SEM micrographs. The pigments used to depict mural painting and groundwater were also analysed by micro-Raman and ICP-MS, respectively, indicating that they are unlikely manganese sources. Unstained building materials, such as granite ashlars, historic joints, mortars and phyllite rocks, were also analysed by ICP-MS showing that historic joints and mortars present significant concentrations of manganese, possibly associated to their absorbing feature. The main materials with potential to impart manganese to Mn-rich patinas are granite ashlars and phyllites. The aim of this investigation is to reveal and ascertain the hypothetical sources and the phenomenon responsible for the Mn-rich black-blue patina appearance, both on mural painting and granite ashlars.