| 摘要: | PAHs在環境中是無所不在的，通常源自於石油中，經加熱、燃燒不完全或油品洩漏所造成。一般而言，石油中含有萘、菲、蒽等多種多環芳香族化合物，而苯環結構穩定不易分解，去除方式除了可利用氧化方式之外，亦可利用生物分解方式來處理，而生物降解適合用於大範圍之現地土壤，且具有經濟上之優勢，因此可選擇使用為石油汙染整治之最佳方式。本研究比較不同加油站排水溝汙泥所馴化篩選出之菲降解菌株E12、E4、N2、M1、L2、L3，進行革蘭氏染色皆為革蘭氏陽性菌，並利用PAHs 16S rDNA 引子進行PCR反應，進行菌種之親源關係。經16S rDNA定序結果比對六菌株兩兩之遺傳距離為0.000-0.597，L2 / L3與 N2 / E4皆為0.000，顯示應為同種菌株，而NJ樹狀圖中可以顯示出菌株可以分為三大群。Rhodococcus sp.菌種為單系群（monophyly）是石油中常見的降解菌之一，且N2、E4菌株與菲降解菌株Rhodococcus sp. 之親緣關係最為接近，其中經遺傳距離之分析，N2、E4菌株可能為Rhodococcus sp. 屬；而E12可能為Bacillus megaterium菌種，L2、L3菌株應為同種菌株；而在親緣樹狀圖中M1菌株與其他菌株之親緣關係極為遙遠，可能為其他菌種。
針對菲降解菌的降解、共代謝及界面活性劑（Tween80、Triton X-100）對於菌株之影響分別探討。結果顯示菲降解及共代謝測試中，E12、M1、L3菌株之降解效果較為顯著，其中L3菌株於共代謝測試中降解效果較好；而試驗菌株於Tween80界面活性劑測試中比Triton X-100生長較好。此外，選出三株降解效率較好之試驗菌株進行土壤模擬試驗，實驗中發現L3試驗菌株於粘板岩沖積土(粘壤土)中有較好的降解效果。
Polyaromatic hydrocarbons (PAHs) are ubiquitous in the environment, they are generally formed by imcomplete combustion of fossil fuels. The common compounds of PAHs are such as naphthalene, phenanthrene and antracene, they are known to be toxic, mutagenic, and carcinogenic to humans and other organisms. However, the efficiency of PAHs biodegradation is limited due to these compounds have two or more fused benzene rings, very low aqueous solubility and vapour pressure. The remediation technologies from a variety of chemical oxidation and biological nmethods that can be used to remove these compounds from polluted sites. Bioremediation is regarded as an alternative method with low cost to degrade PAHs from the large contaminated sites. In this study, the phenanthrene degraders are isolated from the exposed sludge samples from various petroleum stations in southern Taiwan. The isolated strains in this study are E12, E4, N2, M1, L2 and L3. They are all Gram positive based by Gram stain. Phylogenetic relationship of the isolated strains was identified by 16S rDNA gene fragment. The genetic distance of six strains was from 0.000 to 0.597, between E4 and N2, L2 and L3 all were 0.000 shows that the each two strains should be the same. NJ tree indicated that all strains can be divided into three groups. One of the common oil-degrading bacteria, Rhodococcus sp., was a monophyletic group, and closest with N2 and E4 should belong to same genus. E12 may be Bacillus megaterium, and L2 was similar with L3. The relationship was far away with M1 and other strains.
The biodegradation assay of phenanthrene, effect of cometabolism and surfactants (Tween80 and Triton X-100) were also discussed in aqueous media inoculation with test strains, respectively. E12, M1 and L3 could carry out efficient degradation of phenanthrene as carbon and energy source. L3 is the most efficient degrader of phenanthrene when it co-metabolized with low concentration of glucose. The higher growth rate of test strains was obtained when Tween80 was used as surfactant instead of TritonX-100. L3 strain was able to mineralize phenanthrene in slate alluvial soil (clayey loam) suspension. |
