Book of Abstracts (PDF) - International Mycological Association
Book of Abstracts (PDF) - International Mycological Association
Book of Abstracts (PDF) - International Mycological Association
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IMC7 Tuesday August 13th Lectures<br />
199 - Biochemical and molecular aspects <strong>of</strong> lignin<br />
degradation by Pleurotus species<br />
A.T. Martínez 1* , F.J. Ruiz-Dueñas 1 , M. Perez-Boada 1 , P.<br />
Ferreira 1 , S. Camarero 1 , F. Guillen 1 , M.J. Martínez 1 , T.<br />
Choinowski 2 & K. Piontek 2<br />
1 CIB, CSIC, Velazquez 144, E-28006 Madrid, Spain. -<br />
2 ETHZ, Universitätstr. 16, Zurich, Switzerland. - E-mail:<br />
ATMartinez@cib.csic.es<br />
Pleurotus species are investigated due to their ability to<br />
degrade lignin selectively. Their ligninolytic system is<br />
different from that <strong>of</strong> the model white-rot basidiomycete<br />
Phanerochaete chrysosporium. Extracellular<br />
oxidoreductases have been characterized from Pleurotus<br />
eryngii including versatile peroxidase (VP), aryl-alcohol<br />
oxidase (AAO) and laccases. These enzymes are <strong>of</strong><br />
biotechnical interest for degradation <strong>of</strong> lignin, aromatic<br />
compounds and dyes. P. eryngii laccases oxidize lignin via<br />
natural redox mediators and contribute to oxygen activation<br />
by redox cycling <strong>of</strong> lignin-derived quinones. AAO and VP,<br />
which have been recently cloned, crystallized and<br />
expressed in Escherichia coli and Emericella nidulans, are<br />
characteristic <strong>of</strong> the ligninolytic system <strong>of</strong> Pleurotus (and<br />
Bjerkandera) species. AAO provides hydrogen peroxide<br />
for peroxidase activity and generation <strong>of</strong> active oxygen<br />
species. VP represents a third type <strong>of</strong> ligninolytic<br />
peroxidase combining the catalytic properties <strong>of</strong> lignin<br />
peroxidase and manganese peroxidase (first described in P.<br />
chrysosporium) due to an hybrid molecular architecture<br />
including sites for oxidation <strong>of</strong> both Mn(II) and aromatic<br />
substrates. AAO and VP molecular models were obtained<br />
by homology modeling (using crystal structures as<br />
templates), and the VP crystal structure has been recently<br />
solved. Future studies include confirmation <strong>of</strong> active sites<br />
by site-directed mutagenesis, and modulation <strong>of</strong> catalytic<br />
properties by protein engineering techniques.<br />
200 - Role <strong>of</strong> reactive oxygen species in wood decay by<br />
fungi<br />
K.E. Hammel<br />
USDA Forest Products Lab, One Gifford Pinchot Drive,<br />
Madison, WI 53705, U.S.A. - E-mail:<br />
kehammel@facstaff.wisc.edu<br />
Extracellular reactive oxygen species (ROS) have long<br />
been thought to have a biodegradative function in wood<br />
decay by fungi, but the nature <strong>of</strong> these species and the<br />
mechanisms for their production have not been elucidated.<br />
We monitored the hydroxylation <strong>of</strong> a synthetic aromatic<br />
polymer, phenethyl polyacrylate, to estimate the magnitude<br />
<strong>of</strong> extracellular ROS production by two brown rot<br />
basidiomycetes, Gloeophyllum trabeum and Postia<br />
placenta, on cellulose. The results showed that ROS<br />
production was sufficient to account for much <strong>of</strong> the<br />
cellulose depolymerization in the cultures. Both fungi<br />
produced extracellular 2,5-dimethoxyhydroquinone, a<br />
64<br />
<strong>Book</strong> <strong>of</strong> <strong>Abstracts</strong><br />
metabolite that rapidly reduces ferric iron and dioxygen,<br />
thus yielding hydroxyl radicals via the Fenton reaction. We<br />
purified and characterized a G. trabeum flavoprotein<br />
NADH:quinone reductase that probably drives this<br />
chemistry by regenerating the hydroquinone. The gene that<br />
encodes the reductase shares substantial similarity with<br />
quinone reductase genes <strong>of</strong> other fungi, including some<br />
nonlignicolous species.<br />
201 - Biotechnological applications <strong>of</strong> wood decay fungi<br />
E. Srebotnik * , M. Weisgram & K. Messner<br />
Institute <strong>of</strong> Chemical Engineering, Getreidemarkt 9, A-<br />
1060 Vienna, Austria. - E-mail:<br />
esrebot@mail.zserv.tuwien.ac.at<br />
The ligninolytic systems <strong>of</strong> white-rot fungi have great<br />
potential for applications in wood-processing such as<br />
pulping, pulp bleaching and wood composite manufacture.<br />
For example, the use <strong>of</strong> white-rot fungi to treat wood chips<br />
prior to mechanical pulping (biopulping) is already<br />
approaching industrial scale. Furthermore, the low<br />
specificity <strong>of</strong> these systems allows for the conversion <strong>of</strong><br />
various aromatic pollutants and industrial wastes such as<br />
contaminated soil (bioremediation). These processes<br />
involve the use <strong>of</strong> white-rot fungi or their ligninolytic<br />
enzymes to treat polycyclic aromatic hydrocarbons (PAH),<br />
polychlorinated biphenyls and other hazardous xenobiotics.<br />
Whether to apply living fungi or isolated enzymes will<br />
depend on the specific properties <strong>of</strong> the material to be<br />
treated. For example, biopulping takes advantage <strong>of</strong> the<br />
fact that white-rot fungi not only produce a complete set <strong>of</strong><br />
enzymes but can also transport these enzymes into wood<br />
chips and create the appropriate physiological conditions<br />
for enzymatic reactions. However, processes involving<br />
living organisms are relatively difficult to control. Thus,<br />
the use <strong>of</strong> isolated enzyme systems would be preferable in<br />
those cases, where the compounds to be treated are freely<br />
accessible such as in soil extracts. This presentation will<br />
give a brief overview <strong>of</strong> biotechnological applications <strong>of</strong><br />
white-rot fungi and their ligninolytic enzymes and discuss<br />
in more detail the use <strong>of</strong> laccase for the bioremediation <strong>of</strong><br />
PAH.<br />
202 - Some approaches to the evaluation <strong>of</strong> the white<br />
rot basidiomycetes ligninolytic activity<br />
V.I. Elisashvili * , E. Kachlishvili, N. Tsiklauri, T.<br />
Khardziani & M. Bakradze<br />
Institute <strong>of</strong> Biochemistry and Biotechnology, 10 km<br />
Agmashenebeli kheivani,380059 Tbilisi, Georgia. - E-mail:<br />
velisashvili@hotmail.com<br />
Ligninolytic activity <strong>of</strong> basidiomycetes from different<br />
taxonomic groups has been extensively. The production<br />
patterns and levels <strong>of</strong> laccase and Mn-dependent<br />
peroxidase (MnP) differed among species and strains <strong>of</strong> the