Microbial Degradation of Hydrocarbons

Abstract

The filamentous fungus, Cunninghamella elegans, oxidizes naphthalene, biphenyl, benzo[a]-pyrene, benzo[a]anthracene and 3-methyIcholanthrene to the same metabolic products that are formed by mammals. The initial oxidation products are apparently arene oxides that cani somerize to phenols or undergo enzymatic hydration to form trans-dihydrodiols. In the case of benzo[a]pyrene evidence was obtained for the formation of (+)-9α,10α-epoxy-7ß,8α-dihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene which has been implicated as the ultimate carcinogenic benzo[a]pyrene metabolite formed by higher organisms. In contrast, bacteria oxidize naphthalene, biphenyl, benzo[a]pyrene, benzo[a]anthracene and 3-methylcholanthrene to dihydrodiols in which the hydroxyl groups have a cis relative stereochemistry. Arene oxides have not been detected as intermediate products. Many monocyclic aromatic hydrocarbons are also oxidized through cis-dihydrodiols by bacteria and the enzyme catalyzing the dioxygenation of toluene to cis-toluene dihydrodiol has been shown to be a multienzyme system composed of a flavoprotein and two iron sulfur proteins. The differences in the metabolism of aromatic hydrocarbons by bacteria, fungi and mammals may represent a fundamental difference between procaryotic and eucaryotic cells and is almost certainly related to the physiological functions of the different enzyme systems. © 1982, Taylor & Francis Group, LLC. All rights reserved.