Enhancing the production of hydroxyl radicals by Pleurotus eryngii via quinone redox cycling for pollutant removal.
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), Mn(2+), 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 Fe(3+)-EDTA. The main reactions involved in OH production under these conditions have been shown to be (i) DBQ reduction to hydroquinone (DBQH(2)) by cell-bound dehydrogenase activities; (ii) DBQH(2) oxidation to semiquinone (DBQ(-)) by laccase; (iii) DBQ(-) autoxidation, catalyzed by Fe(3+)-EDTA, producing superoxide (O(2)(-)) and Fe(2+)-EDTA; (iv) O(2)(-) dismutation, generating H(2)O(2); 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 Mn(2+), respectively, and 3.1-fold by substituting Fe(3+)-EDTA with Fe(3+)-oxalate. A 6.3-fold increase was obtained by combining Mn(2+) and Fe(3+)-oxalate. These increases were due to enhanced production of H(2)O(2) via anisaldehyde redox cycling and O(2)(-) reduction by Mn(2+). They were also caused by the acceleration of the DBQ redox cycle as a consequence of DBQH(2) oxidation by both Fe(3+)-oxalate and the Mn(3+) generated during O(2)(-) 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.
Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
Víctor
V
Gómez-Toribio
Ana B
AB
García-Martín
María J
MJ
Martínez
Angel T
AT
Martínez
Francisco
F
Guillén
D001547:Benzaldehydes / Q000378:metabolism; D016227:Benzoquinones / Q000378:metabolism*; D004492:Edetic Acid / Q000378:metabolism; D004785:Environmental Pollutants / Q000378:metabolism*; D005290:Ferric Compounds / Q000378:metabolism; D017665:Hydroxyl Radical / Q000378:metabolism*; D008345:Manganese / Q000378:metabolism; D019815:Oxalic Acid / Q000378:metabolism; D010084:Oxidation-Reduction; D020076:Pleurotus / Q000378:metabolism*
D001547:Benzaldehydes; D016227:Benzoquinones; D004785:Environmental Pollutants; D005290:Ferric Compounds; C030511:2,6-dimethoxy-1,4-benzoquinone; D017665:Hydroxyl Radical; C004532:quinone; D008345:Manganese; D019815:Oxalic Acid; D004492:Edetic Acid; C024896:4-anisaldehyde; C019179:Fe(III)-EDTA