Microbial degradation of styrene: biochemistry, molecular genetics, and perspectives for biotechnological applications

Abstract

Large quantities of the potentially toxic compound styrene are produced and used annually by the petrochemical and polymer-processing industries. It is as a direct consequence of this that significant volumes of styrene are released into the environment in both the liquid and the gaseous forms. Styrene and its metabolites are known to have serious negative effects on human health and therefore, strategies to prevent its release, remove it from the environment, and understand its route of degradation were the subject of much research. There are a large number of microbial genera capable of metabolizing styrene as a sole source of carbon and energy and therefore, the possibility of applying these organisms to bioremediation strategies was extensively investigated. From the multitude of biodegradation studies, the application of styrene-degrading organisms or single enzymes for the synthesis of value-added products such as epoxides has emerged.

Styrene oxide isomerase of Sphingopyxis sp. Kp5.2

“…1b) (Mooney et al, 2006;. It has been supposed that this pathway represented the major route to mineralize styrene by micro-organisms (Mooney et al, 2006).…”

Analysis of the Pseudomonas putida CA-3 proteome during growth on styrene under nitrogen-limiting and non-limiting conditions

“…Molecular investigations of the styrene degradation pathway in this organism have been reported (Mooney et al, 2006b;O'Connor et al, 2001). Styrene metabolism in P. putida CA-3 proceeds via initial side chain oxidation and involves an upper pathway converting styrene to phenylacetic acid (PA) (O'Connor et al, 1995), and a lower pathway initiated via activation of PA to phenylacetyl-CoA.…”

“…Styrene metabolism in P. putida CA-3 proceeds via initial side chain oxidation and involves an upper pathway converting styrene to phenylacetic acid (PA) (O'Connor et al, 1995), and a lower pathway initiated via activation of PA to phenylacetyl-CoA. The further metabolism of phenylacetyl-CoA involves oxidation of the aromatic nucleus, followed by ring cleavage and oxidation of the alicyclic compound, eventually yielding TCA cycle intermediates (MartinezBlanco et al, 1990;Mooney et al, 2006b;O'Leary et al, 2002b;Olivera et al, 1998). The pha operon in P. putida CA-3 consists of two class II MCL-PHA synthases (phaC1 and phaC2) flanking the PHA depolymerase-encoding phaZ gene (O'Leary et al, 2005).…”

“…These two abilities have been employed in the two-step chemo-biotechnological conversion of polystyrene, a non-biodegradable polymer, to mclPHA at laboratory scale (Ward et al, 2006). The process has been improved through the controlled feeding of N to the growth medium, which results in a twofold increase in biomass and a 1.4-fold increase in mclPHA accumulation (Goff et al, 2007).Molecular investigations of the styrene degradation pathway in this organism have been reported (Mooney et al, 2006b;O'Connor et al, 2001). Styrene metabolism in P. putida CA-3 proceeds via initial side chain oxidation and involves an upper pathway converting styrene to phenylacetic acid (PA) (O'Connor et al, 1995), and a lower pathway initiated via activation of PA to phenylacetyl-CoA.…”

Mutations at the putative active cavity of styrene monooxygenase: Enhanced activity and reversed enantioselectivity

“…Styrene monooxygenase (SMO) is an enzyme involved in the upper catabolic pathway of styrene degradation (Bestetti et al, 2004;Mooney et al, 2006). It is a member of the class E flavoprotein monooxygenases, which is composed of the oxygenase (StyA) and the reductase (StyB) domains.…”