Mould growth on building materials: Secondary metabolites, mycotoxins and biomarkers
Nielsen, K.F
2002 Dissertation, The Mycology Group, Technical University of Denmark
Nielsen, K.F, (2002), "Mould growth on building materials: Secondary metabolites, mycotoxins and biomarkers", Dissertation, The Mycology Group, Technical University of Denmark.
Abstract:
The aim of this study was to document if the moulds produce mycotoxins and other biologically active metabolites when growing in buildings, as well as investigate the influence of environmental conditions on the production of these metabolites. The growth of moulds under various humidities should also be investigated along with the use of chemical biomarkers fo r quantitation of mould growth.
It was shown that Stachybotrys chartarum produced a number of mycotoxins when growing in buildings. These components were produced in significantly higher quantities than by other moulds investigated in this study. Only 35% of the isolates from buildings produced the extremely cytotoxic satratoxins. Actually these metabolites are probably not responsible for idiopathic pulmonary hemosiderosis in infants, which is probably caused by other S. chartarum me tabolites.
For the first time ever Stachybotrys metabolites were found in air-samples, where several classes of spiriocyclic drimanes and satratoxins were detected. Aspergillus versicolor produced high quantities of the carcinogenic mycotoxin, sterigmatocystin at water activities (aw) > 0.95. At lower aw more than 10 unknown metabolites were produced, including at least 5 metabolites also produced by A. ochraceus. A. versicolor was often growing in mixed cultures with others moulds where it sporulated poorly, meaning that it may evade detection based on cultivating methods. The A. ustus isolates from buildings were macro-morphologically and chemically very different from the cereal isolates, and should be described as a new species. Penicillium chrysogenum produced few detectable metabolites and often none when growing on materials. Combined with the no observed effects on persons experimentally exposed to high quantities of the spores, these observations implies that this species may not be important and is actually obscuring the detection of more toxic genera and species. P. brevicompactum produced mycophenolic acid and P. polonicum the tremorgenic verrucosidin when they were inoculated on water-dama ged materials.
Chaetomium globosum produced high quantities of chaetoglobosins whereas Trichoderma species did not produce detectable quantities of trichothecenes when growing on materials. Even on laboratory media <1% of the isolates produced trichodermol or esters of it. Ergosterol content of building materials was quickly and precisely quantified by isotope dilution GC-MS/MS. Determination of ergosterol is only needed as a supplement for assessing mould growth on test materials, as visual assessment, especially supported by dissection microscopy generally was just as sensitive. The minimal RH for growth on wood based materials and material containing starch was just below 80% at room temperature, and increased to about 90% at 5ˇăC. On paper-mineral composites such as gypsumboard the minimal RH was approx. 90% RH from room temperature to 5ˇăC. Pure mineral based materials with few organic additives seem to be able to support growth at RH = 0.90, although =95% RH was needed to generate chemical dete ctable quantities of biomass. The phylloplane Cladosporium was able to outgrow P. chrysogenum on materials under transient humidities. This is presumably why phylloplanes like Cladosporium, Ulocladium, Phoma and Aureobasidium are very common in bathrooms and other places with instationary humidity con ditions.
Mould growth in buildings is causing various health effects among the occupants, however the causal components is still partly unknown making scientifically based guidelines for "how much is too much" and cost efficient re mediation of mouldy buildings almost impossible.
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Mycology at Technical University of Denmark, DTU "a multi-disciplinary approach our fundamental research today covers all aspects of fungal evolution, secondary metabolism, mycotoxin production, physiology and ecology."
