A multiproxy approach to evaluate biocidal treatm entson biodeteri orated majolica glazed tiles

23 páginas.-- 10 figuras.-- 6 tablas.-- 88 referencias.-- Supporting information Additional Supporting Information may be found in the online version of this article at the publisher’s web-site: http://dx.doi.org/10.1111/1462-2920.13380The Fishing House located on the grounds of the Marquis of Pombal Palace, Oeiras, Portugal, was built in the 18th century. During this epoch, Portuguese gardens, such as the one surrounding the Fishing House, were commonly ornamented with glazed wall tile claddings. Currently, some of these outdoor tile panels are covered with dark colored biofilms, contributing to undesirable aesthetic changes and eventually inducing chemical and physical damage to the tile surfaces. Phylogenetic analyses revealed that the investigated biofilms are mainly composed of green algae, cyanobacteria and dematiaceous fungi. With the aim of mitigating biodeterioration, four different biocides (TiO2 nanoparticles, Biotin® T, Preventol® RI 80 and Albilex Biostat®) were applied in situ to the glazed wall tiles. Their efficacy was monitored by visual examination, epifluorescence microscopy and DNA-based analysis. Significant changes in the microbial community composition were observed 4 months after treatment with Preventol® RI 80 and Biotin® T. Although the original community was inactivated after these treatments, an early stage of re-colonization was detected 6 months after the biocide application. TiO2 nanoparticles showed promising results due to their self-cleaning effect, causing the detachment of the biofilm from the tile surface, which remained clean 6 and even 24 months after biocide application.This work was supported by the Portuguese Foundation for Science and Technology (FCT-MCTES) under grant no. SFRH/BD/46038/2008 and project no. UID/EAT/00729/2013. A. Z. Miller acknowledges the support from a Marie Curie Intra-European Fellowship of the European Commission’s 7th Framework Programme (PIEF-GA-2012-328689). Authors acknowledge the Spanish Ministry of Science and Innovation Research Programme in Technologies for the Assessment and Conservation of Cultural Heritage (TCP CSD2007-00058),Peer reviewe