Towards a better comprehension of biodeterioration in earthen architecture: Study of fungi colonisation on historic wall surfaces in Brazil

This study was aimed to describe fungal communities found in biofilms growing on earthen walls (rammed earth, wattle-and-daub and adobe) of rural and semi-urban historical buildings representative of the first phase of the Brazilian coffee cycle (1820–1880), in the upper basin of the Paraiba do Sul river, São Paulo State. The relationship between substrates and such surface-associated microbial communities was also investigated. Fungal biodiversity was significantly higher in rammed earth with respect to the other two techniques. Granulometric analysis showed that rammed earth also contained a higher percentage of coarse soil fraction which is likely to favour the accumulation of water and organic matter. Cellulolytic activity tested positive for the majority of fungi and acidification test showed that fungi exhibit elevated acidifying capacity suggesting that biodeterioration may occur through acid metabolites.