Old dry mold growth seems to emit less bioactive metabolites and surfactants than actively growing microbes

We characterized the toxicity and surfactant properties of old and fresh biomasses of indoor isolates of Trichoderma atroviride,Aspergillus versicolor, Chaetomium sp., Stachybotrys sp. and Rhizopus sp. Toxicity of cell dispersals fromold dry biomasses (> 12 months old) and actively growing molds(< 3 weeks old) was tested as inhibition of proliferation with somatic mammalian cell lines(PK-15 and MNA).Fresh biomasses were up to 100 times more toxic than old dry biomasses. When calculated per conidial particle,100 times more toxicity was associated with the fresh conidia than the old ones.Surfactant activity was detected both in biomass dispersals and exudates. We hypotized that the metabolic state of the fungal growth may influence fungal metabolite emission into indoor air. This information may be important when mouldy buildings are renovated.