Co-metabolism of 2,4-dichlorophenol and 4-Cl-m-cresol in the presence of glucose as an easily assimilated carbon source by Staphylococcus xylosus

Comparison of the ability of Staphylococcus xylosus to degrade 2,4-dichlorophenol and 4-Cl-m-cresol in separate cultures is reported. Bacterial adaptation and the continuous presence of glucose, as a conventional carbon source, were found to stimulate the degrading efficiency of S. xylosus. 4-Cl-m-cresol exhibited higher substrate-induced toxicity with Kig value at 0.25 mM, comparing to 2,4-dichlorophenol (Kig value at 0.90 mM) at initial concentration ranging from 0.1 to 0.5 mM. Degradation rate of 4-Cl-m-cresol was found to decrease only, revealing lower value of inhibition degradation constant (Ki at 0.019 mM) comparing to that of 2,4-dichlorophenol (Ki at 0.41 mM). Both glucose and each one of the chloro-aromatic compounds tested were simultaneously consumed and an increase of chloride ions in the medium appeared, during the exponential phase of growth. The chloride ions increase was nearly stoichiometric in the presence of 2,4-dichlorophenol and one of its several intermediate products identified was 2-Cl-maleylacetic acid. In the case of 4-Cl-m-cresol, only one metabolic product was found and identified as 3-methyl-4-oxo-pentanoic acid.