Soya lecithin effects on the aerobic biodegradation of polychlorinated biphenyls in an artificially contaminated soil

The effects of the phytogenic surfactant soya lecithin (SL) on the aerobic biodegradation of polychlorinated biphenyls (PCBs) spiked into a synthetic soil were studied. Soil was spiked with both biphenyl (4 g/kg) and Fenclor 42 (1,000 mg/kg) and treated in aerobic batch slurry-phase microcosms (17.5 % w/v). Microcosms were prepared either with or without the exogenous aerob ic PCB-dechlorinating bacterial co-culture ECO3 (inoculum: 10(8) CFU/mL). I n some inoculated microcosms, SL was added at 15 or 30 g/kg. Indigenous bac teria having the capability of metabolizing biphenyl and 2-chlorobenzoic ac id were found to develop in the microcosms during the experiment, and were responsible for the significant PCB biodegradation and dechlorination obser ved in the uninoculated controls. The addition of ECO3 bacteria resulted in only a slight PCB biodegradation increase. In the presence of SL, a higher availability of biphenyl- and chlorobenzoic acid-degrading bacteria and hi gher PCB biodegradation and dechlorination yields were observed; the effect s increased proportionally with the concentration of the applied SL. A sign ificant decrease of soil ecotoxicity was also revealed in SL-supplemented m icrocosms. At both concentrations, SL was found to be a good carbon source for both the indigenous and ECO3 bacteria, as well as a product capable of enhancing the PCB bioavailability in the microcosms. (C) 2000 John Wiley & Sons, Inc.