Research on fungal growth and production of volatile fungal metabolites in relation with the 'sick building syndrome'

Ondertitel:Onderzoek naar schimmelgroei en productie van vluchtige fungale metabolieten in relatie met het 'sick building syndrome'

In the last decades, the increasing reporting of non-specific symptoms experienced by the occupants of a building with poor indoor air quality, such as headache, nausea and irritation of skin, eyes and airways, has brought about the neologism Sick Building Syndrome (SBS). The causative agents of SBS are not identified but indoor dampness is consistently associated with a wide range of respiratory health effects, for which microorganisms are recognized as the main causal factors. In the first part of this research, 11 damp and moldy buildings were simultaneously sampled for the presence of mycotoxins and fungi to reveal their occurrence in indoor environments and for (microbial) volatile compounds ((M)VOCs) to evaluate their use as indicators of mold growth. Several techniques for (M)VOC sampling and air, surface and dust fungal samplings were applied. The presence of one or more mycotoxins was shown in 56 % of the analyzed samples, and some of these mycotoxins, relevant from a human health prospective, were significantly associated with respirable particles. In general, the presence of mycotoxins matched well with the isolated fungal species or strains in the same samples, showing that fungal isolations were well-performed. Concerning (M)VOC samplings, the finding of eight VOCs (out of 133) typically derived by fungal metabolism was achieved in two of the building samplings effectuated, including geranyl acetone, α-copaene and trans-calamenene. These three volatile compounds were successively shown to be characteristic for Aspergillus ustus strains, which were recovered from the same house. Another aim of this study was to highlight species- or genus-specific MVOCs or MVOC patterns suitable to be used in chemotaxonomy (attempt to classify and identify organisms according to their biochemical composition). Therefore, 255 fungal strains isolated from the 11 sampled buildings were analyzed for MVOC production after growth on a common artificial substrate (Malt Extract Agar, MEA) by means of SPME-GC-MS. In several cases, the value of MVOCs in chemotaxonomy could be demonstrated and the conclusions were supported by statistical analysis of the data. As a last task of this extensive study, five of the isolated fungi were selected for a detailed further study in which the MVOC production was investigated under several growth conditions, namely four temperatures, four relative humidity values, three substrates (MEA, wallpaper and plasterboard) and four inoculum concentrations. In parallel, the influence of these same conditions on the radial growth on MEA was tested to relate the metabolite production to the biomass present. In general, fungal growth and MVOC production were more pronounced on MEA (as expected) while growth on the two building materials tested entailed the production of some characteristic compounds. The influence of temperature and relative humidity on growth and metabolism is different for different fungal species. Two main patterns of behavior were observed. Moreover, 6-pentyl-2-pyrone, the main MVOC produced by a Trichoderma atroviride strain, was tested for irritation of mucus membranes. The amounts of 6-pentyl-2-pyrone classified in the Slug Mucosal Irritation assay as irritating and damaging the mucosal membrane corresponded to a possible indoor contamination. Also, a collected extract of volatiles of Penicillium decumbens was tested for antifungal activity by means of three antifungal tests. The volatile metabolites (containing mainly (+)-thujopsene) inhibited the growth of five out of 16 fungi.

ISBN:9789059894358

Jaar van publicatie:2011

Toegankelijkheid:Closed