Volatile metabolites from microorganisms in indoor environments sampling, analysis and identification
Sammanfattning: Microorganisms are able to produce a wide variety of volatile organic compounds. This thesis deals with sampling, analysis and identification of such compounds, produced by microorganisms commonly found in buildings.The volatiles were sampled on adsorbents and analysed by thermal desorption cold trap-injection gas chromatography, with flame ionization and mass-spectrometric detection. The injection was optimized, with respect to the recovery of adsorbed components and the efficiency of the chromatographic separation, using multivariate methods. Eight adsorbents were evaluated with the object of finding the most suitable for sampling microbial volatiles. Among the adsorbents tested, Tenax TA proved to have the best properties for the purpose. Some carbon-containing adsorbents, e.g., Tenax GR and Carbopack B, showed a catalytic effect on thermal decomposition of some compounds, mainly terpene derivatives.Five fungal species, Aspergillus versicolor, Pénicillium commune, Cladosporium cladosporioides, Paecilomyces variotii and Phialophora fastigiata, and anactinomycete, Streptomyces albidoflavus, were cultivated on various artificial media and/or building materials. Cultivation was performed in culture flasks, provided with air inlet and outlet tubes. Humidified air was constantly led through the flasks, and samples were taken by attaching adsorbent tubes to the outlet tubes of the flasks. The cultivation medium proved to be of vital importance for metabolite production, quantitatively as well as qualitatively. For Streptomyces albidoflavus the effect of medium, cultivation temperature, and oxygen and carbon dioxide levels in the supplied air on the production of volatiles, was studied using multivariate techniques. The medium and the temperature exerted the largest influence, but the oxygen and carbon dioxide levels also affected the amounts of some metabolites produced.The produced volatile metabolites were identified by mass spectrometry and reference compounds. Alcohols, ketones, sulphur compounds and terpenes were most frequently found, but hydrocarbons, ethers and esters were also produced by some species. Among the most commonly produced metabolites, which are also suggested as potential indicator substances for excessive growth of microorganisms in buildings, were 3-methyl-1-butanol, 2-methyl-1-butanol, 3-methyl-2-butanone, 3-methyl-2-pentanone, dimethyl disulphide, -methylfuran, 2,5-dimethylfuran and geosmin.
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