[Isolation and Identification of a Chlorobenzene-degrading Bacterium and Its Degradation Characteristics]

A bacterium strain LW26 which could utilize chlorobenzene (CB) as sole carbon and energy source was isolated from a biotrickling filter reactor treating CB-contaminated off-gas. Based on its morphological and physiological characteristics, as well as the analysis of 16S rRNA gene sequence and Biolog test, the strain LW26 was identified as Delftia tsuruhatensis. To our best knowledge, it is the first time that the strain Delftia tsuruhatensis was applied for CB purification. In this study, the effects of temperature, pH, initial CB concentration and Cl^- concentration on the biodegradation were investigated. The results showed that the optimal temperature and pH for CB biodegradation were 25℃ and 7.0,respectively; the maximum CB tolerated concentration for LW26 was as high as 500 mg·L^-1; when the concentration of Cl^- was above 0.14 mol·L^-1, the CB degradation was significantly restrained. The degrading process of the strain LW26 followed the Haldane kinetic model and the maximum specific growth rate and the maximum specific degradation rate were 0.42 h^-1 and 2.53 h^-1, respectively.GC-MS analysis of the metabolites revealed that CB was firstly converted to o-chlorophenol by strain LW26. Combined with the activity of catechol dioxygenase, it can be speculated that CB was finally mineralized to CO₂, or converted to cell biomass after processes of ortho cleavage,dechlorination and oxidation.