Abstract
Biodegradation of phenanthrene by activated sludge was studied. Intermediates of phenanthrene by biodegradation were analyzed by gas chromatography-mass spectrometry, and the metabolic pathways were discussed.Two grams (1, 0.5, and 0.5 g at intervals of 2 days) were added to the aeration vessel (10l) containing activated sludge to which the synthetic sewage medium was continuously fed at 10 ml/min. The control aeration vessel contained the medium without addition of phenanthrene. One hundred liter of effluent from the laboratory activated-sludge unit was collected for a week, and filtered with glass wool. After adjusting to pH 3-4, the filtrate was passed through an Amberlite XAD-2 resin (20-50 mesh) column (4×12 cm) to extract metabolites of phenanthrene. The metabolites were eluted with 500 ml of ether from the XAD-2 column. The ether extract was concentrated to 50 ml with Kuderna Danish evaporator and the extract was separated into the neutral and acid fraction.3, 4-Dihydroxy-3, 4-dihydrophenanthrene, 3, 4-phenanthraquinone, and 7, 8-benzocoumarin were found in the neutral polar fraction separated by silica-gel column chromatography. Acid metabolites were methylated by using diazomethane and dimethylformamide dimethylacetal, and 12 kinds of acid methabolites were found. The presence of 2-hydroxy-1-naphthoic acid in acid metabolites suggest new biodegradation pathway via naphthalene-1, 2-dicarboxylic acid.
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