Biodegradation of UV-irradiated polychlorinated biphenyls in surfactant micelles

Potential enhancement of biodegradability of commercial polychlorinated biphenyls (PCBs) mediated by photodechlorination was investigated. Used in tandem, photolysis and biodegradation of Aroclor 1242 (MW≈260), a commercial PCB mixture, dissolved in micellar solution of a nonionic surfactant, polyoxyethylene 10 lauryl ether (POL(10)), was studied. A mixed population of two genetically engineered microorganisms (GEMs), Pseudomonas putida IPL5∷TnPCB and Ralstonia eutropha B30P4∷TnPCB, was used for the aerobic biodegradation of POL (10) while cometabolizing Aroclor 1242. UV-irradiation at 254 nm for 40 minutes caused 63% degradation of Aroclor 1242 in a solution containing 210 mg/L of PCB congeners in 4 g/L POL(10). In the same period, 42% of the PCB chlorine appeared as chloride in solution. Gas chromatograms of UV-irradiated Aroclor 1242 solutions indicated that almost all biorecalcitrant PCB congeners, especially the highly chlorinated ones, were photolyzed. PCB GEMs removed an additional 30 mg/L (14.3%) of the PCBs in 96 hr from the UV-irradiated micellar PCB solution. Seemingly, the products of photolysis did not inhibit biodegradation of the remaining congeners or the surfactant.