METABOLISM OF CRESOLS BY THE PHENOL-ADAPTED CELLS OF Candida tropicalis ISOLATED FROM ACTIVATED SLUDGE

Abstract

An yeast strain that utilizes phenol as sole carbon source was isolated from activated sludge, and identified as Candida tropicalis. The cells utilized catechol and methylcatechol for growth as a sole carbon source, but not cresols, hydroxybenzoates and protocatechuate. The yeast cells could rapidly oxidize cresols after the cells were adapted to phenol. The cells oxidized m-cresol and accumulated metabolite in the reaction mixture. Chemical structure of the m-cresol metabolite was identified as 5-formyl-2-hydroxy-4-methyl-2, 4-pentadienoic acid by the UV and IR absorptions, and by the Rf value of paperchromatography. The cells hydroxylate m-cresol to form 4-methylcatechol, and the benzene ring is oxidized by the meta-type fission. The metabolite of o-cresol oxidation suggests that the oxidation may occur through catechol and the benzene ring is cleaved. These results suggest that the yeast strain has catechol oxygenase, but not protocatechuate oxygenase. The pathway of cresol oxidation in the cells is probably initiated by the formation of phenol hydroxylase and catechol oxygenase induced by phenol.