|摘要: ||多環芳香族碳氫化合物是由二個或以上的苯環經鍵結反應而形成，通常經由化石燃料的不完全燃燒、廢棄物燃燒與碳氫化合物之意外洩漏而污染環境，因其多為高親脂性結構，容易吸附於土壤顆粒中，故於環境中有高度持久性，且其於環境中的持久性則隨多環芳香族碳氫化合物(Polycyclic Aromatic Hydrocarbons，縮寫為PAHs)的分子量提高而提高。近年來，高分子量PAHs因具生物毒性、致突變性與致癌性，且在土壤環境中分布甚廣，故廣泛受到學者之重視。處理PAHs污染的技術，包括：溶劑萃取、生物降解、植物復育、化學氧化與熱處理等。芘(pyrene)為四環芳香族碳氫化合物，與其他具致癌性PAHs之化學結構相似，在土壤分布甚廣，為環境中主要的PAH污染物。生物復育(bioremediation)因具有低化學品添加與低耗能條件下，將芘轉化為低/無毒性的物質，深入探討微生物降解芘將有助於未來實際應用於PAH污染之復育。
本研究是以生物復育之方式應用於受芘污染之土壤，由南台灣地區不同加油站及化工廠周邊之排水溝污泥做為菌種分離源，以100 mgL-1的芘為唯一碳源與能源之基礎培養基，進行增殖培養以馴養可降解芘的菌株，並篩選、純化各分離菌株，再測試各降解菌株對芘的最高耐受濃度，藉挑選降解能力較佳之試驗菌株。經16S rDNA序列鑑定後，菌株H1、L1及N1與Bacillus cereus及Bacillus thuringiensis相似(99%)；R1之相似菌種為Escherichia coli (96%)；菌株W1與Bacillus megaterium相似(98%)；FA之相似菌株為Klebsiella pneumonia (99%)。
針對芘降解菌的生物降解、共代謝及界面活性劑(Tween80、Triton X-100)對於菌株之影響分別探討。各試驗菌株於Tween80界面活性劑中生長狀況較於Triton X-100中良好。在芘之降解及共代謝測試中，W1與N1菌株之降解效果較佳，且外加葡萄糖促進各試驗菌種共代謝芘的測試中，所有菌株均有提高降解效率之功效。最後模擬受芘污染之土壤以生物復育法進行處理，結果顯示菌株W1及N1於100 mg kg-1芘之砂頁岩沖積土壤中的降解效果較為顯著。此外，當添加1g kg-1 soil葡萄糖進行共代謝試驗，結果得知菌株W1及N1降解芘的效果更為明顯。
PAHs are aromatic hydrocarbons with two or more fused benzene rings. These compounds enter into the environment via many ways including incomplete combustion of fossil fuels, waste incineration, as well as accidental spilling of hydracarbons. PAHs are hydraphobic pollutants highly persistent in soil environment. Their persistence increase with increase in the molecular weight. The environmental fate of PAHs is of concern cause of their mutagenicity, ecotoxicity, and carcinogenic potential of high molecular weight PAHs. The remediation technologies for PAH-contaminated soils include solvent extraction, bioremediation, phytoremediation, chemical oxidation, thermal treatment. Pyrene, a four-ring PAH with structural similarity to several carcinogenic PAHs, is a widespread pollutant in the soil environment, and, it is one of the most predominant PAH in the environment. Bioremediation is the tool to transform pyrene to less/non harzardous forms with less input of chemicals and energy. Thus, a deeper understanding of the pyrene biodegradation will facilitate better ways to remediate pyrene pollution.
In this study, the pyrene degraders are isolated from the sludge samples from various disposing sties of petroleum stations and factories in southern Taiwan and enrichment was carried out with 100 mgL-1 pyrene as a sole carbon and energy source in a mineral medium. The tolerance of pyrene by the isolates was investigated to select the effective pyrene degraders. The 16S rDNA sequence of H1, L1 and N1 had 99% indentity to Bacillus cereus and Bacillus thuringiensis strains. R1 stain best matched to Escherichia coli (96% indentity). W1 might be closely related to Bacillus megaterium (98% indentity), and FA was similar with Klebsiella pneumoniae (99% indentity).
The biodegradation assay of pyrene, effect of cometabolism and surfactants (Tween80 and TritonX-100) were also discussed in aqueous media inoculation with isolted strains, respectively. The higher growth rate of test strains was obtained when Tween80 was used as surfactant instead of TritonX-100. W1 and N1 could carry out efficient degradation of pyrene as a carbon and energy source in mineral medium. All strains degrade pyrene more efficient when it co-metabolized with low concentration of glucose. N1 and W1 strains showed the higher degradation activity to mineralize 100 mg kg-1 pyrene in sandy alluvial soil. In addition, the degradtion of pyrene in soil suggested the potential application of two islates (W1 and N1) with adding co-metabolism substrates (1g kg-1 soil) in bioremediation.