engleski

Enrichment of polychlorinated biphenyl-degrading bacteria

The main objective of our study was to prepare seed cultures for enhancing transformation of polychlorinated biphenyls (PCBs) in contaminated soil of the power substation TS 110/35 kV Zadar, Croatia, damaged during warfare operations in 1991. A microcosm enrichment approach was employed with the aim to enrich long-term biphenyl-adapted bacteria from polluted soil as potential active cultures for PCB transformation. Seven soil samples, taken from top layer, were collected in polluted area of the Zadar power substation and two soil samples at airport areas in Omišalj and Trogir, Croatia. Bacterial growth was stimulated by incubating soil in mineral medium with biphenyl as the only carbon source. Enrichment experiments resulted in the selection of two most active mixed cultures originating from the power substation soil (TSZ7) and Trogir airport soil (AIR-TR). Both selected cultures showed substantial PCB-degradation capability (56, 5% to 60% of PCB50 commercial mixture, containing congeners from di- to octachlorobiphenyles, was reduced after a two week culturing in the presence of biphenyl as supplemental carbon source). They displayed similar and broad substrate specificity and reduced less chlorinated congeners more effectively than highly chlorinated ones. Chloroacetophenone and chlorobenzoic acids were found as degradation products indicating that both cultures expressed 2, 3- and 3, 4-dioxygenase activity. Future PCB biotransformation studies will focus on the assessment of growth kinetics of the selected cultures as well as the factors that affect kinetics of PCB degradation with the aim of providing basic parameters for planning small-scale-field biodegradation experiments in contaminated soil. It is expected that in site biological treatment of these chemicals will be a more practical, more efficient and less costly remediation strategy than conventional remediation methods.

polychlorinated biphenyl; biodegradation; enrichment cultivation

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