Formation of PCB degrading biofilm on sorptive surfaces by Burkholderia xenovorans strain

Student: Freshta Akbari (Dept. of Biological Sciences)

Faculty Adviser: Birthe V. Kjellerup (Dept. of Biological Sciences)


Polychlorinated biphenyls (PCBs) are persistent organic pollutants that can be found in soil and sediment. PCBs are known to cause cancer and other adverse health effects thus their presence in the environment is unwanted and biodegradation is sought after. Specific bacteria can degrade PCBs. Biodegradation of PCBs can be enhanced by utilizing biofilms formed on the surface of granular activated carbon (GAC) as they adsorb PCBs thus keeping them out of the food chain, while they simultaneously biodegrade PCBs. The objective of this project was to evaluate the biofilm formation of the aerobic PCB degrader Burkholderia xenovorans strain LB400 on GAC and bentonite and to survey the presence of PCB degraders in wastewater.

Cultures of LB400 were grown in M9 media spiked with biphenyl (5 mM), Aroclor 1221 (50 ppm), shaking at 30°C with GAC (3%) and bentonite (3%). Q-PCR with specific primers for aerobic PCB degradation was performed together with direct cell count using DAPI. Q-PCR results at Day 0 showed 1.7x107 (GAC) and 3.8x107 (bentonite) cells/ml, while direct cell count showed biofilm formation on GAC and bentonite with 3.0x108 and 1.5x108 cells/ml, respectively, after 3 weeks (Day 0: 106 cells/ml). The data suggests that the GAC and bentonite surfaces enhanced the growth of LB400 via biofilm formation. Samples from a wastewater treatment plant showed that aerobic PCB degraders were present in numbers ranging from 4.3x102 (Incoming waste water), 2.0x107 (mixed liquor), 3.0x108 (waste activated sludge), 2.5x105 (gravity sludge) and 1.7x105 cells/ml (dried pellets) cells/g dry matter. 

Click here for the research poster presented at the Fifth Annual Landmark Conference Summer Research Symposium