Kinetics of 2,4-dichlorophenol and 4-Cl-m-cresol degradation by Pseudomonas sp. cultures in the presence of glucose

Abstract

Comparison of the ability of Pseudomonas sp. to degrade 2,4-dichlorophenol and 4-Cl-m-cresol in separate cultures in the presence of glucose, as a conventional carbon source, is reported. The specific growth rates at 0.1 mM 2,4-dichlorophenol and 4-Cl-m-cresol were estimated to be 0.181 and 0.154 h(-1), respectively, showing that Pseudomonas sp. is mainly inhibited by 4-Cl-m-cresol. The percentage of consumption ranges between 65% and 11% for 2,4-dichlorophenol and between 37% and 8% for 4-Cl-m-cresol, respectively, depending on its initial concentration. The dechlorination of the two compounds was investigated in the growth media and it was found that chloride liberation in the case of 2,4-dichlorophenol took place during the exponential phase of growth, followed by pH decrease from 6.1 to 5.8 at 0.1 mM. In contrast, in the case of 4-Cl-m-cresol chloride ion release was observed to a lesser extent, indicating the different metabolic pathway of 4-Cl-m-cresol. 2,4-Dichlorophenol and 4-Cl-m-cresol degradation followed a first-order kinetics model, whereas glucose consumption fitted well a zero-order kinetics model.