The effect of nano-TiO2 and plant extracts on microbial strains isolated from Theban ancient Egyptian royal tomb painting

Mural paintings in ancient Egyptian tombs in West Thebes have been suffering from several deterioration factors and symptoms such as variations of temperatures and relative humidity, salts efflorescence and crypto-florescence, crackling and bio-deterioration effects, which assimilate in insects, algae, actinomycetes, etc. Other causing factors are bacteria and fungi, which accelerate mechanical weathering, chemical changes and aesthetic deterioration, like the penetration of mycelium below plaster layers, decomposition, disintegration, alterations and discoloration. These micro-organisms can excrete organic and inorganic acids, alkaline compounds, chelating, enzymes substances and pigments. Three fungi strains (Fusarium oxysporum, Rhizopus stolonifer and Aspergillus flavus) and two bacteria strains (Staphylococcus warnei and Micrococcus luteus) were isolated from the royal Theban tombs paintings (west Thebes, Luxor, Egypt). This work aimed to access the presence of microorganisms and their effect on mural paintings deterioration; it also studies their treatment methods, such as nanoparticles (TiO2 NPs) and Sesbania sesban and Ricinus communis plant extract (PE). The applied doses of NPs and PE did not cause any observable alterations or color changes to pigments and binding media (arabic gum) used in the paintings. TiO2 NPs 160 ppm and 100 mg of plant extracts were the efficient concentration level in eliminating microbial growth. The causes of the different efficacy of the treatments are observed, as well as the potential risks of recolonization by viable cells left behind after treatment.