Cooxidation of chloro- and methylphenols by Alcaligenes xylosoxidans JH1 |
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Authors: | Hollender Juliane Hopp Johannna Dott Wolfgang |
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Affiliation: | (1) Institut für Hygiene und Umweltmedizin, RWTH Aachen, Pauwelsstr. 30, 52074 Aachen, Federal Republic of Germany;(2) Fachbereich Medizintechnik, Fachhochschule Jena, Tatzendpromenade 1b, 07749 Jena, Federal Republic of Germany |
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Abstract: | Alcaligenes xylosoxidans subspecies denitrificans JH1 was enriched with 2-chlorophenol from a mixed culture degrading different chloro- and methylphenols. The strain used all monochloro- and monomethylphenols apart from 2-methylphenol as sole source of energy and carbon with stoichiometric release of chloride. 4-Chlorophenol was mineralized up to a concentration of 1.3 mM. Degradation of mixtures of monochloro- and monomethylphenols occurred at least partially except for the mixture of 2-chlorophenol and 3-methylphenol. Depending upon the growth substrates used, enzymes of the ortho and/or meta cleavage pathway catalysed the degradation of the phenols. The transformation of chlorophenols was concluded to occur exclusively via the ortho cleavage pathway because no chlorocatechol 2,3-dioxygenase activity was found in chlorophenol-grown cells. Degradation of 4-methylphenol in strain JH1 occurred both by the ortho and meta cleavage pathway as indicated by the finding that the ortho- and meta-cleaving dioxygenases were expressed in 4-methylphenol-grown cells. Transformation of methylphenols by the ortho cleavage pathway led to the accumulation of methyllactones as dead-end products. Mixtures of methyl- and chlorophenols were metabolized mainly by the ortho cleavage pathway because chlorocatechols formed inactivated the constitutive catechol 2,3-dioxygenase which caused channelling of methylphenols into the ortho cleavage pathway. |
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Keywords: | Alcaligenes chlorophenol methylphenol meta cleavage pathway ortho cleavage pathway |
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