Aerobic degradation of 3,3′,4,4′-tetrachlorobiphenyl by a resuscitated strain Castellaniella sp. SPC4: Kinetics model and pathway for biodegradation

Resuscitated strains which were obtained by addition of resuscitation promoting factor (Rpf) could provide a vast majority of microbial source for obtaining highly efficient polychlorinated biphenyl (PCB)-degrading bacteria. In this study, the Castellaniella sp. strain SPC4 which was resuscitated by Rpf addition showed the highest efficiency in degradation of 3,3',4,4'-tetrachlorobiphenyl (PCB 77) among the resuscitated and non-resuscitated isolates. Further investigations on the PCB 77 degradation capability of the resuscitated strain SPC4 showed that SPC4 could efficiently degrade PCB 77 with maximum degradation rate (qmax) of 0.066/h at about 20 mg/L of PCB 77. The maximum growth rate on PCB 77 was 2.663 × 107 CFU/(mL·h) (0.024/h). The most suitable model of Edward demonstrated that the SPC4 could achieve qmax of 0.9315/h, with substrate-affinity of 11.33 mg/L and substrate-inhibition constants of 11.41 mg/L. Meanwhile, the presence of bphA gene expression and chlorine ions release, together with the identification of metabolites, confirmed that the bph-encoded biphenyl pathway was involved in PCB 77 mineralization by SPC4. This report is the first to demonstrate aerobic degradation of PCB 77 by the resuscitated strain Castellaniella sp. SPC4, indicating excellent potential for PCB bioremediation.