[Monochlorophenols as enzyme substrates for the preparatory metabolism of phenol in Candida tropicalis yeasts].

The object of this work was to find out whether Candida tropicalis can be used for monochlorophenol degradation. Phenol monooxygenase and pyrocatechase, enzymes involved in preparatory phenol metabolism were shown to catalyse transformation of 3- and 4-chlorophenols. Phenol monooxygenase catalyses hydroxylation of 3- and 4-chlorophenols to 4-chloropyrocatechol which yields beta-chloromuconic acid under the action of pyrocatechase. Synthesis of phenol monooxygenase is induced by 3- and 4-chlorophenols. beta-Chloromuconic acid is a terminal product of 3- and 4-chlorophenol transformation under neutral conditions. In a weakly acid medium (the Rieder medium, phosphate buffer, pH 5.5), transformation of these chlorophenols terminates with spontaneous lactonization of beta-chloromuconic acid and its dehalogenation. C. tropicalis hardly transforms 2-chlorophenol although certain oxygen uptake occurs in its presence. 3- and 4-chlorophenols are not nutrient sources for C. tropicalis. The yeast has not been adapted to 3- and 4-chlorophenols as sole nutrient sources.