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

Abstract

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.

Roles of Thermophiles and Fungi in Bitumen Degradation in Mostly Cold Oil Sands Outcrops

“…Although pure cultures of Mycobacterium, Rhodococcus, Burkholderia, Stenotrophomonas, and Sphingomonas can degrade HMW PAHs such as pyrene, benzo[b]fluorene, and benz[a]anthracene (13,17,43,50), biodegradation rates were significantly increased in fungal-bacterial cocultures (51). The role of fungi in these cocultures is thought to be the catalysis of extracellular oxidative reactions through enzymes similar to those used in lignin degradation (51)(52)(53)(54)(55)(56), including fungal P450 monooxygenases (55).…”

“…The action of specific enzymes also suffers if structurally similar compounds act as competitive inhibitors. Hence, although microorganisms which can grow by degrading specific NAs (15,16) or PAHs (17) have been isolated, these substrates degrade more slowly when present at ultralow concentrations in a bitumen mixture. For example, NA mixtures representing 10 3 to 10 4 compounds from oil sands bitumen end up in tailings ponds at concentrations of up to 100 mg/liter (18).…”

Aerobic Degradation of Fluoranthene, Benzo(b)Fluoranthene and Benzo(k) Fluoranthene by Aerobic Heterotrophic Bacteria- Cyanobacteria Interaction in Brackish Water of Bodo Creek

“…Forinstance, Maeda et al [24] reported on transformation of Benzo(k)fluoranthene into four, three and two aromatic ring products after exposure to Sphingobium sp strain KK22. Degradation of Benzo(k)fluoranthene achieved 10% biotransformation in the first five days and between this to 10 days biodegradation continued with approximately 73% of Benzo(k)fluoranthene recovered from culture media on the tenth day though it did not support the growth of strain KK22 as a sole source of carbon and energy.…”

“…The identification of the downstream products 9-hydroxy-fluoranthene-8-carboxylic acid and 1,8-naphthalic anhydride for instance, which may have occurred through 8,9-carbon position initial attack on the benzo(k)fluoranthene molecule provides a clear evidence in support of biotransformation mechanism by microorganisms. The first ring fission event of the benzo(k)fluoranthene molecule occurred by ortho-ring cleavage and resulted in 8-carboxyfluoranthenyl-9-propenic acid, a product that corresponded to [M -H] − = 315, and this is the first report of this product from PAH biodegradation [24]. Ichor et al [1,36] reported on effective biodegradation of total petroleum hydrocarbons and mineralization of phenanthrene a LMW PAHs by the consortium of aerobic heterotrophic bacteria and cyanobacteria from Bodo creek respectively.…”

“…Two Marinobacters, M. sedimentalis and M. falvimaris were isolated from hypersaline sabkhas due to their capability to grow on crude oil and were observed to have utilized Tween 80 and other individual aliphatic hydrocarbons ranging from C 9 -C 40 as carbon sources in the presence of 6% NaCl [22]. Dastgheib et al [23] [24]. Benzo(k)fluoranthene as a member of the five-ring HMW PAH class was observed to resist biotransformation due to its molecular stability, hydrophobic nature and low water solubility, which is approximately 1 ug L −1 or less [25][26][27].…”