Affiliation:
1. Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu 9, 28040 Madrid, Spain
2. Departamento de Microbiología y Parasitología, Universidad de Alcalá, Ctra. Madrid-Barcelona Km. 33.600, 28871 Alcalá de Henares, Madrid, Spain
Abstract
ABSTRACT
A simple strategy for the induction of extracellular hydroxyl radical (OH) production by white-rot fungi is presented. It involves the incubation of mycelium with quinones and Fe
3+
-EDTA. Succinctly, it is based on the establishment of a quinone redox cycle catalyzed by cell-bound dehydrogenase activities and the ligninolytic enzymes (laccase and peroxidases). The semiquinone intermediate produced by the ligninolytic enzymes drives OH production by a Fenton reaction (H
2
O
2
+ Fe
2+
→ OH + OH
−
+ Fe
3+
). H
2
O
2
production, Fe
3+
reduction, and OH generation were initially demonstrated with two
Pleurotus eryngii
mycelia (one producing laccase and versatile peroxidase and the other producing just laccase) and four quinones, 1,4-benzoquinone (BQ), 2-methoxy-1,4-benzoquinone (MBQ), 2,6-dimethoxy-1,4-benzoquinone (DBQ), and 2-methyl-1,4-naphthoquinone (menadione [MD]). In all cases, OH radicals were linearly produced, with the highest rate obtained with MD, followed by DBQ, MBQ, and BQ. These rates correlated with both H
2
O
2
levels and Fe
3+
reduction rates observed with the four quinones. Between the two
P. eryngii
mycelia used, the best results were obtained with the one producing only laccase, showing higher OH production rates with added purified enzyme. The strategy was then validated in
Bjerkandera adusta
,
Phanerochaete chrysosporium
,
Phlebia radiata
,
Pycnoporus cinnabarinus
, and
Trametes versicolor
, also showing good correlation between OH production rates and the kinds and levels of the ligninolytic enzymes expressed by these fungi. We propose this strategy as a useful tool to study the effects of OH radicals on lignin and organopollutant degradation, as well as to improve the bioremediation potential of white-rot fungi.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
134 articles.
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