Journal Article

Biotransformation of the high‐molecular weight polycyclic aromatic hydrocarbon (PAH) benzokfluoranthene by Sphingobium sp. strain KK22 and identification of new products of non‐alternant PAH biodegradation by liquid chromatography electrospray ionization tandem mass spectrometry

Nishi, Shinro, Kanaly, Robert A., Ozeki, Yasuhiro, Maeda, Allyn H., Hatada, Yuji

2014

Overview

Summary A pathway for the biotransformation of the environmental pollutant and high‐molecular weight polycyclic aromatic hydrocarbon (PAH) benzo[k]fluoranthene by a soil bacterium was constructed through analyses of results from liquid chromatography negative electrospray ionization tandem mass spectrometry (LC/ESI(–)‐MS/MS). Exposure of Sphingobium sp. strain KK22 to benzo[k]fluoranthene resulted in transformation to four‐, three‐ and two‐aromatic ring products. The structurally similar four‐ and three‐ring non‐alternant PAHs fluoranthene and acenaphthylene were also biotransformed by strain KK22, and LC/ESI(–)‐MS/MS analyses of these products confirmed the lower biotransformation pathway proposed for benzo[k]fluoranthene. In all, seven products from benzo[k]fluoranthene and seven products from fluoranthene were revealed and included previously unreported products from both PAHs. Benzo[k]fluoranthene biotransformation proceeded through ortho‐cleavage of 8,9‐dihydroxy‐benzo[k]fluoranthene to 8‐carboxyfluoranthenyl‐9‐propenic acid and 9‐hydroxy‐fluoranthene‐8‐carboxylic acid, and was followed by meta‐cleavage to produce 3‐(2‐formylacenaphthylen‐1‐yl)‐2‐hydroxy‐prop‐2‐enoic acid. The fluoranthene pathway converged with the benzo[k]fluoranthene pathway through detection of the three‐ring product, 2‐formylacenaphthylene‐1‐carboxylic acid. Production of key downstream metabolites, 1,8‐naphthalic anhydride and 1‐naphthoic acid from benzo[k]fluoranthene, fluoranthene and acenaphthylene biotransformations provided evidence for a common pathway by strain KK22 for all three PAHs through acenaphthoquinone. Quantitative analysis of benzo[k]fluoranthene biotransformation by strain KK22 confirmed biodegradation. This is the first pathway proposed for the biotransformation of benzo[k]fluoranthene by a bacterium. Identification of products produced by a soil bacterium from the biotransformation of the 5‐ring PAH benzo[k]fluoranthene by using LC/ESI‐MS/MS techniques. Results from the biotransformation of 3‐ and 4‐ring structurally analogous PAHs by the same strain were used to confirm the biotransformation pathway proposed for benzo[k]fluoranthene.

• Publisher: John Wiley & Sons Ltd
• Subject: Acenaphthenes - metabolism / Biotransformation / Chromatography, Liquid / Fluorenes - metabolism / Metabolic Networks and Pathways / Polycyclic Aromatic Hydrocarbons - metabolism / Spectrometry, Mass, Electrospray Ionization / Sphingobium / Sphingomonadaceae - metabolism / Tandem Mass Spectrometry