The ability of filamentous fungi to produce acids on indoor building materials

Sixty two filamentous fungi isolated from paint coatings, wallpaper, carton-gypsum board, and indoor air in buildings were screened for acid activity. It was found that 64.5% of strains produce acids on medium with bromo-cresol purple, where 18% of the strains were distinguished by very high acid activity (acid activity coefficient Q = 1.32-2.83), including the species: Aspergillus niger, Aspergillus versicolor, Penicillium expansum, Penicillium brevicompactum, Penicillium chrysogenum, Cladosporium cladosporioides, Stachybotrys chartarum, Mucor globosus, Ulocladium chartarum and Alternaria alternata. Research indicated that filamentous fungi considerably decrease the pH of the medium when that medium containing building material. The greatest acid production and pH decrease of the medium was observed during the growth of filamentous fungi in a medium with mortar, while the production of acids was less in a medium with carton-gypsum board, gypsum, and wallpaper. Filamentous fungi produced succinic, oxalic, malic and fumaric acids in the medium with indoor building materials. It was stated that the type of building material affects the spectrum and quantity of organic acids produced by filamentous fungi.