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Applied and Environmental Microbiology, June 2009, p. 3954-3962, Vol. 75, No. 12
0099-2240/09/$08.00+0     doi:10.1128/AEM.02138-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Enhancing the Production of Hydroxyl Radicals by Pleurotus eryngii via Quinone Redox Cycling for Pollutant Removal{triangledown}

Víctor Gómez-Toribio,1,{dagger} Ana B. García-Martín,2 María J. Martínez,1 Ángel T. Martínez,1 and Francisco Guillén2*

Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu 9, 28040 Madrid, Spain,1 Departamento de Microbiología y Parasitología, Universidad de Alcalá, Ctra. Madrid-Barcelona Km. 33.600, 28871 Alcalá de Henares, Madrid, Spain2

Received 15 September 2008/ Accepted 13 April 2009

The induction of hydroxyl radical (OH) production via quinone redox cycling in white-rot fungi was investigated to improve pollutant degradation. In particular, we examined the influence of 4-methoxybenzaldehyde (anisaldehyde), Mn2+, and oxalate on Pleurotus eryngii OH generation. Our standard quinone redox cycling conditions combined mycelium from laccase-producing cultures with 2,6-dimethoxy-1,4-benzoquinone (DBQ) and Fe3+-EDTA. The main reactions involved in OH production under these conditions have been shown to be (i) DBQ reduction to hydroquinone (DBQH2) by cell-bound dehydrogenase activities; (ii) DBQH2 oxidation to semiquinone (DBQ–) by laccase; (iii) DBQ– autoxidation, catalyzed by Fe3+-EDTA, producing superoxide (O2–) and Fe2+-EDTA; (iv) O2– dismutation, generating H2O2; and (v) the Fenton reaction. Compared to standard quinone redox cycling conditions, OH production was increased 1.2- and 3.0-fold by the presence of anisaldehyde and Mn2+, respectively, and 3.1-fold by substituting Fe3+-EDTA with Fe3+-oxalate. A 6.3-fold increase was obtained by combining Mn2+ and Fe3+-oxalate. These increases were due to enhanced production of H2O2 via anisaldehyde redox cycling and O2– reduction by Mn2+. They were also caused by the acceleration of the DBQ redox cycle as a consequence of DBQH2 oxidation by both Fe3+-oxalate and the Mn3+ generated during O2– reduction. Finally, induction of OH production through quinone redox cycling enabled P. eryngii to oxidize phenol and the dye reactive black 5, obtaining a high correlation between the rates of OH production and pollutant oxidation.

* Corresponding author. Mailing address: Departamento de Microbiología y Parasitología, Facultad de Farmacia, Universidad de Alcalá, Ctra. Madrid-Barcelona, Km. 33.600, 28871 Alcalá de Henares, Madrid, Spain. Phone: 34918854635. Fax: 34918854663. E-mail: francisco.guillen{at}uah.es

{triangledown} Published ahead of print on 17 April 2009.

{dagger} Present address: Varian Iberica S.L., Avda. Pedro Diez 25, 28019 Madrid, Spain.

Applied and Environmental Microbiology, June 2009, p. 3954-3962, Vol. 75, No. 12
0099-2240/09/$08.00+0     doi:10.1128/AEM.02138-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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