O efeito da radiação gama na descontaminação microbiológicas de pinturas: um estudo de caso em uma obra de Portinari

Abstract

The cultural heritage consists in one set of works of arts that represent the identity of a given society and the historical legacy left to future generations. These assets are subject to several deterioration mechanisms, among which biodeterioration by microorganisms stands out. The knowledge of the fungal community associated the cultural heritage and of the physicochemi characteristics of the substrate are important subsidies for the understanding of the deteriogenic processes and their causes, it contributes to the determination of a disinfection treatment that is effective and does not cause damage to the work. In this, the present study entitled “the effect of gamma radiation on microbiological decontamination of paintings: a case study of Portinari's work” was developed from the mural painting “Frevo” dated 1961, by the painter italian brazilian. This painting is part of the Pampulha landscape complex, which constitutes a cultural heritage of humanity, a title granted by UNESCO. Thus, this work consisted of physicochemical (non-destructive) analyzes of six pictorial fragments collected from the painting, using techniques such as stratigraphic study, infrared and Raman spectroscopy, and scanning electron microscopy to identify the materials and techniques used. by the artist in the execution of the work. Pigments such as lead oxide (PbO 2 ), titanium oxide (TiO 2 ), zinc oxide (ZnO 2 ) and calcium carbonate (CaCO 3 ) filler were found in the preparation base, and, in the pictorial layers, the yellow and red of cadmium (CdSBaSO 4 and CdS. CdSe), cobalt blue (CoO.Al 2 O 3 ), phthalocyanine blue and green (CuC 32 H 16 N 8 and CuC 32 Cl 16 - n H n N 8 ), iron oxide (Fe 2 O 3 /FeO 2 ), lapis lazuli (Na 6-8 A l6 Si 6 O 24 S 2-4 ) and the binder found was linseed oil (C 18 H 32 O 2 ). Additionally, microbiological samples were collected on the pictorial surface and microbiological analyses were performed consisted of fungal isolation, cultivation, morphological and molecular identification using universal oligonucleotides for the ITS4 and ITS5 ribosomal regions. Thus, fourteen fungal species belonging to eight different families, six were identified: (Apiosporaceae belonging to families) with the corresponding four families Aspergillus and Penicillium, two (Didymellaceae) two identified genera are Epicoccum and Didymella, (Apiosporaceae Arthrinium) (Hypocreaceae, Trichoderma) (Caphaeriaceae Pleurostoma), (Chaetomiaceae Chaetomium), (Mytilinidiacea Mytilinidion) and (Sporidiobolaceae Rhodotorula).Enzymatic screening assays of the isolated fungi were also carried out to evaluate the production of enzymes, and few fungi were considered producers of xylanase and cellulase. Based on the physical-chemical tests, a minimum inhibitory concentration test was carried out to verify the growth of the isolates in pure components of the substrate, the result found was that most fungi grow in the pure compounds tested. The fungal isolates were also submitted to cobalt 60 gamma irradiation in three dosages 1kGy, 3kGy and 5 kGy, these were tested in spore solution and mycelium on plates, and the control groups were also made for the experiment. Regarding to the treatment by irradiation of the spore solutions, practically all the dosages tested were effective, as for the mycelia, all the fungi showed low sensitivity to the irradiation dosages. Based on the above-

mentioned integrated analyses, the present work has contributed to the conservation and preservation of cultural heritage, specifically paintings.