Escola Superior de Biotecnologia
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Browsing Escola Superior de Biotecnologia by Sustainable Development Goals (SDG) "11:Cidades e Comunidades Sustentáveis"
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- Exploring new sustainable solutions based on chitosan and cellulose crystals towards the preventive conservation of cultural heritagePublication . Silva, Nádia Suati Caetano da; Costa, Patrícia Raquel Fernandes de Melo Moreira da; Pintado, Maria Manuela Estevez; Madureira, Ana Raquel Mendes Ferreira MonteiroOutdoor sculptures made of stone and mortar are a significant part of the worldʼs cultural heritage. Consequently, their conservation is of great importance, mainly due to their vulnerability to deterioration. Deterioration occurs as a combination of factors that cause alterations and devalue the artworks over time, including those resulting from biodeterioration mechanisms triggered by the growth and activity of microorganisms. Developing sustainable strategies to slow down the proliferation of microorganisms is necessary to reduce the negative environmental and human health impacts of currently used toxic biocides. Hence, this thesis aims to contribute to developing low-toxicity and more sustainable antimicrobial coatings for the preventive conservation of stone heritage, particularly outdoor sculptures. Firstly, an evaluation of the biocontamination and microbiological composition of five outdoor sculptures, made of different materials and located in the district of Porto (Portugal), was performed. Two methodologies were tested to collect samples from the sculptures in a non-invasive and non-destructive way: cotton swabs (classical approach) and poly(2-hydroxyethyl methacrylate) cryogels (alternative method). The quantification and determination of the cell viability of the microorganisms collected were performed by flow cytometry, which proved to be an analytical technique of interest for microbiological studies of cultural heritage. Both methods were effective, although higher concentrations of microorganisms were collected with swabs, while data visualisation of viable and non-viable cells was clearer with cryogels. Consequently, swab samples were taken to characterise the epilithic bacterial and fungal communities of the sculptures. High-throughput sequencing revealed great taxonomic diversity and species richness, including in well-preserved sculptures. Fungal diversity was lower than that of the bacterial communities. Proteobacteria was the core taxa common to all the sculptures. Ascomycota were also detected in all the sculptures and Basidiomycota were a significant part of the microbiomes in granite, where an abundance of pigment-producing microorganisms was also found. Additionally, colourimetry and adenosine triphosphate quantification assays quickly identified contaminated areas of the sculptures. The next stage of the work dealt with the preparation and characterisation of chitosan formulations, to be used as antimicrobial coatings to inhibit the growth of microorganisms in sculptures. The first set of formulations consisted of chitosan solutions containing citric acid and different concentrations of sodium tripolyphosphate (CHGCA-TPP), which were polymerised into films for their characterisation. Fourier transform infrared (FTIR) spectroscopy confirmed the establishment of cross-linking interactions, and the films exhibited partial wettability (40.81-31.44°), solubility (43.64-55.14%) and swelling (123.36-75.17%) in water, but allowed water vapour exchanges due to their high permeability (140.055-372.575 g m-2 d). The films reduced the growth of microorganisms that commonly colonise stone heritage: Staphylococcus aureus (0.87-1.58-log reduction), Bacillus cereus (ca. 1-3-log reduction), Rhodotorula spp. (between 0.73-1.27-log reduction and complete inhibition) and Penicillium chrysogenum (11.92-21.48% inhibition). Another set of formulations was prepared to enhance the properties of the CHGCA-TPP formulations. A screening was conducted with chitosan solutions containing microcrystalline cellulose (MCC) or cellulose nanocrystals, and the chosen formulation was supplemented with oregano essential oil (OEO) at 1% and 2%. Cross-linking interactions and incorporation of OEO were confirmed by FTIR analysis of the films, which remained poorly soluble (15.74-16.85%), with low percentages of swelling (16.10-28.22%) and relatively low wettability (> 70°). These formulations are an improvement on the CHGCA-TPP ones, including their antimicrobial action, since the films containing 2% OEO completely inhibited the growth of S. aureus, Rhodotorula spp. and P. aeruginosa, induced ca. 60% inhibition of P. chrysogenum and reduced the growth of B. cereus. Lastly, the two most promising formulations (CHGCA-TPP-a and 2-MCC-OEO-2) were tested in granite, limestone and marble samples. Both formulations polymerised on the stones’ surfaces, as confirmed by scanning electron microscopy and FTIR spectroscopy, but formed irregular coatings. The CHGCA-TPP-a coating reduced the wettability of granite and limestone, while 2-MCC-OEO-2 did the same in a more pronounced way and in all stone types. Neither coating caused visible colour changes when the formulations were applied with a brush. In vitro antimicrobial assays with stone samples inoculated with selected strains showed that CHGCA-TPP-a inhibited the growth of B. cereus, Rhodotorula spp. and P. aeruginosa in granite after 7 days to ca. 4 to 5 log10 (CFU mL -1 ). In contrast, 2-MCC-OEO-2 reduced the concentrations of viable cells in all stone types to ca. 3 to 5 log10 (CFU mL -1 ) depending on the strain. In situ antimicrobial assays, where samples were placed in an outdoor setting, showed that CHGCA-TPP-a did not have an inhibitory effect under the conditions tested, with concentrations of viable cells equal to or higher than those of uncoated slabs, regardless of the mode of application of the formulation (deposition with a micropipette or spreading by brush) or the number of treatments over the assay period. However, multiple applications of 2-MCC-OEO-2 with a micropipette over time reduced the concentrations of viable cells in granite and marble, but the same occurred only in limestone when the coating was applied with a brush. In conclusion, this work added to the knowledge of the biocontamination and diversity of the microbiomes of outdoor sculptures, in particular of the Porto district in Portugal, which can help outline future conservation strategies. The chitosan formulations tested, especially those with MCC and OEO, are a potential base for further development and optimisation of novel low-toxicity antimicrobial coatings towards more sustainable preventive conservation strategies of stone heritage.
- Mass tourism, cultural heritage, and traditional values within citizen lifestyle in Porto (Portugal): an overview through the HAC4CG projectPublication . Vieira, Eduarda; Pelaez, Ana; Rosa, Inês; Lemos, Teresa; Bordalo, Rui; Vasconcelos, Marta; Moreira, PatríciaPorto has a rich urban mesh and unique cultural identity, whose preservation has been the basis of its historic centre classification as a World Heritage Site by UNESCO (1996). The increase in demand of Porto as a tourism destination since 2015 was simultaneously favoured by the opening of Porto’s airport new terminal that greatly powered low-cost companies and the licensing for the rehabilitation of houses for hostels and restaurants. These were factors of opportunity that allowed an exponential growth of tourism and a for-profit rehabilitation process in the entire city without proper control. Beyond the impact on housing and gentrification, mass tourism has had a great impact on the city’s lifestyle. The local community is currently confronted with these rapid metamorphoses, becoming the agent of a process of acculturation that is complex and unsustainable in the long run and with implications in the construction of Identity and future Collective Memory. Furthermore, to attract the newly arrived costumers and their diverse culinary preferences, the traditional local gastronomy has been changed, remodelled, and repackaged. Deep changes were observed either in traditional food consumption value chains as well in the grocery’s stores, markets, and restaurants. This communication aims to highlight the preliminary results of the research conducted under the HAC4GC project.