| Summary: | Two mould fungi, Gliocladium roseum and Verticillium bulbillosum, that had
demonstrated an inherent ability to degrade didecyldimethylammonium chloride (DDAC), were
used in the biodegradation experiments. DDAC was a) added to liquid media or b) used to treat
wood pieces that were then subjected to fungal biodegradation.
A metabolite from the degradation of DDAC in the treated wood was discovered from the
HPLC chromatogram, where the peak due to DDAC decreased and was replaced by a new peak
at a longer retention time. It was isolated by preparative HPLC and further purified. Proton
nuclear magnetic resonance (NMR) and Fourier transformed infrared spectroscopy (FTIR) were
used to identify the metabolite. From the spectra the compound was determined to be a
quaternary ammonium compound (QAC) that differed only slightly from DDAC. The
metabolite had two methyl groups and two decyl groups attached to the central nitrogen, with a
hydroxyl group attached to one of the decyl chains. The hydroxyl group was not at the terminal
carbon of the chain, suggesting that it was not the initiation of P-oxidation of the alkyl chain.
The structure of this metabolite suggested that it was not an intermediate in the
breakdown and possible mineralization of DDAC, but rather it appeared to be a
biotransformation. It was hypothesised that this biotransformation reduced the toxicity of the
DDAC to fungi. This is supported in the literature, which cites many cases of moulds employing
hydroxylating enzymes to detoxify compounds. The two mould fungi and the basidiomycetes,
Postia placenta and Trametes versicolor were used to screen various QACs with oxidized alkyl
chains to determine their toxicity. It was found that a QAC that was heavily oxidized along its
long alkyl chains (QAC-OXID) was significantly less toxic to both the mould fungi and the
basidiomycetes than DDAC. === Forestry, Faculty of === Graduate
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