五氯酚被大量使用在木材防腐上，隨著藥劑的生產及使用所排出大量含五氯酚的廢水，若滲入土壤將是一大污染。氯酚化合物的處理，一般多為物化處理，如活性碳吸附、離子交換、焚化等。這些方法均有其處理效果，但基於費用及二次污染的問題而美制其應用。故本研究將採用生物處理方式，從受五氯酚污染之場址土壤篩選出五氯酚分解菌，並研究菌株的生理特性，進而對污染場址中五氯酚之去有所助益。本研究分離出一株五氯酚分解菌，經16S rDNA序列鑑定菌名為Sphingomonas chlorophenolica；其最佳生長溫度在以濃度400mg/l之葡萄糖為基質時是28℃，以濃度400mg/l之醋酸鈉作基質時，最佳生長溫度則是30℃；在pH值為6.9~7.6時有最佳降解五氯酚能力，濃度75 mg/l之五氯酚分可在37小時內降解完全；菌株對不同五氯酚濃度之降解情形如下：在添加濃度100mg/l五氯酚時，可在25小時達100%降解；添加濃度200mg/l之五氯酚則可在90小時內達到完全降解；當添加濃度400mg/l之五氯酚時，五氯酚在110小時達去除率89%，之後便不再降解；添加較高濃度600及800mg/l之五氯酚時，菌株Sphingomonas chlorophenolica則無法降解五氯酚。本研究所分離出菌株Sphingomonas chlorophenolica其降解五氯酚能力較文獻所提菌株之能力佳。 Pentachlorophenol (PCP) has been widely used as a wood preservative for more than 100 years. This widespread use has rustled in the uncontrolled release of PCP into the soil and aquatic environments. This environmental contamination is significant because PCP has been shown to have a relatively high potential for aqueous phase migration in soils and is considered to be very toxic. Several physical, chemical and biological methods including activated carbon adsorption, ion exchange, incineration and biological degradation have been proposed for treating or recovering chlorophenolic compounds the biological treatment is superior to physicochemical methods such as activated carbon adsorption and incineration because the latter ones have high treatment costs and possibilities of causing a secondary pollution. This study attempts to isolate and identify the PCP degrading bacteria, which utilize PCP as the substrate, from PCP contaminated soils. The performance of the PCP degrading bacteria for treating different initial PCP concentrations was also investigated under aerobic conditions. The results indicated that one strain was isolated from the PCP contaminated soils. This strain was identified as Sphingomonas chlorophenolica were 28℃ and 30℃ by utilizing glucose and sodium acetate as substrates, respectively. When the pH values were 6.9 and 7.6, the PCP removal rate of Sphingomonas chlorophenolica was best and 75 mg/l of PCP was completely removed at 37 hours. When the initial PCP concentrations were 100 mg/l and 250 mg/l, Sphingomonas chlorophenolica could remove PCP completely within 25 hours and 90 hours, respectively. When the initial PCP concentration was 400 mg/l, the removal efficiencies were 89% for 100 hours. When the initial PCP concentration was above 600 mg/l, Sphingomonas chlorophenolica could not degrade PCP. Data from this investigation and previous studies of the degradation of PCP illustrate the potential use of this bacterium to biodegradation of PCP in the contaminated soils.