Biotransformation of Tebuconazole by Microorganisms: Evidence of a Common Mechanism

Diana N. Obanda, Todd F. Shupe


A major problem with organic wood preservatives is biotransformation by both wood decaying and wood-inhabiting but nondecaying microorganisms in long-term service. Detoxification of organic biocides may contribute significantly to treated wood failure. In this study, a bacterium (Pseudomonas fluorescens), mold (Trichoderma harzianum), soft rot (Chaetomium globosum), white rot (Phanerochaete chrysosporium), and brown rot (Meruliporia. incrassata) were used to access the extent of biotransformation and the initial metabolite products of tebuconazole in liquid cultures. This study proposed metabolic pathway(s) and explored the possibility of a common biotransformation mechanism for all species. P. chrysosporium showed little ability to metabolize tebuconazole. Within 21 da, 40.4, 59.9, 68.2, and 70.2% tebuconazole was metabolized by M. incrassata, C. globosum, T. harzianum, and P. fluorescens, respectively, into a form that may be less toxic. Mass spectroscopy and infrared analysis of isolated metabolites indicated that the major pathway was cleavage of the triazole ring on tebuconazole and that most species mainly performed oxidation reactions to form the alcohol monolog, which was further oxidized to form the carboxylic acid analog of tebuconazole. Only T. harzianum metabolized the hydroxyl group on the tert-butyl moiety by acetylation to form an ester.


Biotransformation;preservative tolerance;oxidation;tebuconazole;wood decay

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