Degradation of Polychlorinated Biphenyls (PCBs) Facilitated by Plant Terpenoids as Growth Substances or Inducers

초록

The eventual goal of this study is to elucidate roles of plant terpenoids (e.g., cymene, limonene and others) as natural substrates in the cometabolic biodegradation of PCBs and to develop an effective PCB bioremediation technology. The aim of this study was to examine how plant terpenoid, as natural substrates or inducers would affect the biodegradation of PCB congeners. Various PCB degraders that could grow on biphenyl and several terpenoids were tested for their PCB degradation capabilities. The PCB congener degradation activities were initially monitored through resting cell assay technique that could detect degradation products of the substrate. The congener removal was also confirmed by concomitant GC analysis. The PCB degraders, Pseudomonas sp. P166 and Rhodococcus sp. T104 were found to grow on both biphenyl and terpenoids ((S)-(-) limonene, p-cymene and _-terpinene) whereas Arthrobacter B1B could not grow on the terpenoids as a sole carbon source. The strain B1B grown on biphenyl showed a good degradation activity for 4,4-dichlorobiphenyl (DCBp) while strains P166 and T104 gave about 25% was of B1B activity. The enzyme activity induced by cymene, limonene and terpinene was hardly detected by the resting cell assay technique. This appeared to be due to relatively lower induction effect of these terpenoids compared with biphenyl. A subsequent GC analysis, however, showed that the congener could be removed up to 30% by the resting cells of T104 grown on the terpenoids. This indicates that terpenoids, widely distributed in nature, could be utilized as both growth and/or induction substrates for PCB biodegradation.