Biodegradation aspects of Polycyclic Aromatic Hydrocarbons (PAHs): A review

Mechanisms of membrane toxicity of hydrocarbons.

The intent of this review is to provide an outline of the microbial degradation of polycyclic aromatic hydrocarbons. A catabolically diverse microbial community, consisting of bacteria, fungi and algae, metabolizes aromatic compounds. Molecular oxygen is essential for the initial hydroxylation of polycyclic aromatic hydrocarbons by microorganisms. In contrast to bacteria, filamentous fungi use hydroxylation as a prelude to detoxification rather than to catabolism and assimilation. The biochemical principles underlying the degradation of polycyclic aromatic hydrocarbons are examined in some detail. The pathways of polycyclic aromatic hydrocarbon catabolism are discussed. Studies are presented on the relationship between the chemical structure of the polycyclic aromatic hydrocarbon and the rate of polycyclic aromatic hydrocarbon biodegradation in aquatic and terrestrial ecosystems.

Biodegradation of polycyclic aromatic hydrocarbons

Interest in the biodegradation mechanisms and environmental fate of polycyclic aromatic hydrocarbons (PAHs) is prompted by their ubiquitous distribution and their potentially deleterious effects on human health. PAHs constitute a large and diverse class of organic compounds and are generally

Biodegradation of high-molecular-weight polycyclic aromatic hydrocarbons by bacteria.

Bioremediation of high molecular weight polycyclic aromatic hydrocarbons: a review of the microbial degradation of benzo[a]pyrene.

Polycyclic aromatic hydrocarbon (PAH) biodegradation was investigated in contaminated soils from two different industrial sites under simulated land treatment conditions. Soil samples from a former impregnation plant (soil A) showed high degradation rates of PAHs by the autochthonous microorganisms, whereas PAHs in material of a closed-down coking plant (soil B) were not degraded even after inoculation with bacteria known to effectively degrade PAHs. As rapid PAH biodegradation in soil B was observed after PAHs were extracted and restored into the extracted soil material, the kind of PAH binding in soil B appears to completely prevent biodegradation. Sorption of PAHs onto extracted material of soil B follows a two-phase process (fast and slow); the latter is discussed in terms of migration of PAHs into soil organic matter, representing less accessible sites within the soil matrix. Such sorbed PAHs are suggested to be non-bioavailable and thus non-biodegradable. By eluting soil B with water, no biotoxicity, assayed as inhibition of bioluminescence, was detected in the aqueous phase. When treating soil A analogously, a distinct toxicity was observed, which was reduced relative to the amount of activated carbon added to the soil material. The data suggest that sorption of organic pollutants onto soil organic matter significantly affects biodegradability as well as biotoxicity.

Adsorption of polycyclic aromatic hydrocarbons (PAHs) by soil particles: influence on biodegradability and biotoxicity

Bacterial mixed cultures able to degrade the polycyclic aromatic hydrocarbons (PAH) phenanthrene, fluorene and fluoranthene, were obtained from soil using conventional enrichment techniques. From these mixed cultures three pure strains were isolated:Pseudomonas paucimobilis degrading phenanthrene;P. vesicularis degrading fluorene andAlcaligenes denitrificans degrading fluoranthene. The maximum rates of PAH degradation ranged from 1.0 mg phenanthrene/ml per day to 0.3 mg fluoranthene/ml per day at doubling times of 12 h to 35 h for growth on PAH as sole carbon source. The protein yield during PAH degradation was about 0.25 mg/mg C for all strains. Maximum PAH oxidation rates and optimum specific bacterial growth were obtained near pH 7.0 and 30°C. After growth entered the stationary phase, no dead end-products of PAH degradation could be detected in the culture fluid.

Degradation of phenanthrene, fluorene and fluoranthene by pure bacterial cultures

The degradation of fluoranthene by pure cultures of Alcaligenes denitrificanss WW1, isolated from contaminated soil samples, was investigated. The strain showed maximum degradation rates of 0.3 mg fluoranthene/ml per day. A denitrificans was able to utilize also naphthalene, 1- and 2-methylnaphthalene, phenanthrene, and anthracene as sole carbon sources and to co-metabolize fuuorence, pyrene, and benzo(a)anthracene. During growth on fluoranthene in batch culture two metabolic products that were completely degraded before growth entered the stationary phase were detected in the culture fluid. Anslyses by UV, mass and NMR spectroscopy identified the products as acenaphthenone and 3-hydroxymethyl-4,5-benzocoumarine. Fluoranthene-grown resting cells of A. denitrificans showed degradative activity towards 2,3-dihydroxybenzoic acid, pyrogallol, salicylic acid, and catechol. The enzymatic activities in extracts of fluoranthene-induced cells indicate a meta ring fission involved in the degradation of fluoranthene. From these data new aspects of the biodegradative pathway of fluoranthene have been predicted.

Microbial metabolism of fluoranthene : isolation and identification of ring fission products

At present, many microorganisms are known to degrade polycyclic aromatic hydrocarbons (PAHs) that range in size from naphthalene to pyrene (Gibson 1984, Heitkamp et al. 1988, Mueller et al. 1990, Walter et al. 1991, Weisenfels et al. 1991 ). Under idealized conditions, biodegradation of PAHs is influenced by the transition rate of PAHs into the aqueous phase. Thus, water solubility is the limiting rate factor of microbial PAH degradation concerning flask studies (Wodzinski and Coyle 1974, Stucki and Alexander 1987, Weisenfels et al. 1990a). Nevertheless, studies on biological soil remediation have pointed out that biodegradation of organic pollutants may be inhibited by several abiotic factors (Weisenfels et al. 1990b, van Afferden et al. 1991). It has been shown that one factor causing reduced biodegradability of compounds is sorption on soil particles and organic carbon (Robinson et al. 1990, Manilal and Alexander 1991, Weisenfels et al. 1992).

Walter D. Weissenfels

Papers

Adsorption of polycyclic aromatic hydrocarbons (PAHs) by soil particles: influence on biodegradability and biotoxicity

Degradation of phenanthrene, fluorene and fluoranthene by pure bacterial cultures

Microbial metabolism of fluoranthene : isolation and identification of ring fission products

Adsorption of Polycyclic Aromatic Hydrocarbons (PAHS) by Soil Particles: Influence on Biodegradability and Potential Risk of Contaminated Sites

Bacterial degradation of naphthalene, phenathrene, fluorene and fluoranthene by pure strains.