臺灣北部沿海中2-甲基萘降解細菌的分離及特性研究

Abstract

多環芳香烴 (Polycyclic aromatic hydrocarbons, PAHs) 為近年來備受關注的汙染物，經由水、空氣或食物進入人體。許多多環芳香烴已經被認定為致癌物，臨床實驗報告指出若長期接觸高濃度多環芳香烴混合物，會導致皮膚癌、胃癌或肝癌的產生。研究發現很多細菌可以利用低分子量的PAHs作為單一碳源，將它們轉換為代謝路徑中較簡單受質。 微生物對PAHs的生物分解作用可分為礦化作用 (mineralization)、共代謝作用 (cometabolism) 及非專一性自由基氧化作用 (unspecific radical oxidation)。為了解台灣沿岸海域中具有分解二甲基萘 (2-methylnaphthalene) 能力的細菌種類、不同培養條件對菌株降解二甲基萘的影響、菌株降解二甲基萘的可能機制，本研究以多環芳香烴為單一碳源進行增菌培養，分離出四株可利用二甲基萘為單一碳源的細菌，經16S rRNA基因定序，三株為假單胞菌屬 (Pseudomonas) 及一株為 Cobetia菌屬，而假單胞菌屬中編號ME2具有良好降解活性。利用高效能液相層析儀 (High Performance Liquid Chromatography, HPLC) 探討ME2在不同培養條件下降解二甲基萘的差異，發現在單一碳源的情況下，ME2在pH8、30℃下，培養30天後可將1000 ppm二甲基萘降解 40~50%，而供給有機營養物可促使菌株降解達 70%。

Polycyclic aromatic hydrocarbons (PAHs) pollution has attracted much of attention in recent years. The pollutants can enter the human body through water, air or food. Many of the PAHs are carcinogens. They could cause skin cancer, stomach cancer or liver cancer when human expose to PAHs in high concentrations for a long period of time. It was found that many bacteria can use low molecular weight PAHs as single carbon source and convert them into simple substrates in the metabolic pathway. Microbial biodegradation of PAHs can be classified into mineralization, cometabolism and unspecific radical oxidation. To investigate the bacterial species that have the ability to decompose 2-methylnaphthalene in the coastal waters of Taiwan, the influences of different culture conditions on the degradation of PAHs, and possible mechanisms of 2-methylnaphthalene degradation, the present study used 2-methylnaphthalene as sole carbon source in the enrichment culture. Four bacteria strains were isolated. Strains ME2, ME3 and ME4 are Pseudomonas spp. and strain ME1 is Cobetia sp. Strain ME2 has the best degradation activity. It was chosen for the later study. High performance liquid chromatography (HPLC) was used to investigate the bacterial PAHs degradation ability in different culture conditions. Strain ME2 could degrade 400~500 ppm 2-methylnaphthalene after 30 days at pH 8 and 30 ℃. When supplied with organic nutrients, the degradation ability of ME2 was enhanced up to 700 ppm.