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Ewald Srebotnik

Bio: Ewald Srebotnik is an academic researcher from Vienna University of Technology. The author has contributed to research in topics: Lignin & Phanerochaete. The author has an hindex of 22, co-authored 53 publications receiving 1785 citations. Previous affiliations of Ewald Srebotnik include University of Vienna & United States Department of Agriculture.


Papers
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TL;DR: Information obtained by immunoelectron microscopy and differential staining led to the conclusion that the biopulping effect obtained after 2 weeks of incubation cannot be explained by the direct action of enzymes on lignin or polysaccharides, and a low molecular mass agent is considered to be responsible for the biopsies.
Abstract: Treatment of wood chips with lignin-degrading fungi prior to pulping has been shown to have great potential for mechanical as well as chemical pulping on a laboratory scale. Ceriporiopsis subvermispora, when grown on aspen or loblolly pine for 4 weeks, was found to be superior to other fungi. On aspen there was an energy savings of 47%, and an increase in burst and tear indices of 22% and 119%, respectively. With loblolly pine, energy savings amounted to 37%, while burst and tear indices increased by 41% and 54%, respectively. The weight loss was only 6%, but a decrease in optical properties had to be accepted. After sulfite cooking of wood chips pretreated for 2 weeks, the Kappa number decreased by 30% with hard- and softwood. Tensile and tear indices decreased by only 10%, while the brightness of unbleached pulp increased by 4% with birch. Information obtained by immunoelectron microscopy and differential staining led to the conclusion that the biopulping effect obtained after 2 weeks of incubation cannot be explained by the direct action of enzymes on lignin or polysaccharides. Instead, a low molecular mass agent is considered to be responsible for the biopulping effect. These results have changed the aims of biopulping from an emphasis on removing the bulk of lignin to an emphasis on a short-term process, lasting 2 weeks and yielding a low mass loss. Data on these kinetics of fungal development and the degree of asepsis will help to scale-up the process. An advanced chip pile is assumed to be the most feasible process design, rather than a controlled enclosed reactor.

209 citations

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TL;DR: The method provided a simple and reliable screening procedure that distinguishes between fungi that cause decay by selectively removing lignin and those that degrade both cellulose and lignIn simultaneously.
Abstract: Cryostat microtome sections of birch wood degraded by white rot fungi were examined by light microscopy after treatment with two stains: astra-blue, which stains cellulose blue only in the absence of lignin, and safranin, which stains lignin regardless of whether cellulose is present. The method provided a simple and reliable screening procedure that distinguishes between fungi that cause decay by selectively removing lignin and those that degrade both cellulose and lignin simultaneously. Moreover, morphological characteristics specific to selective delignification were revealed.

189 citations

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TL;DR: High performance liquid chromatography of products from the oxidized models showed that they were produced in sufficient yields to account for the ability of laccase/HOBT to depolymerize nonphenolic lignin.

156 citations

Journal ArticleDOI
TL;DR: Experiments showed that wood block cultures and defined liquid medium cultures of C. subvermispora rapidly depolymerized and mineralized a (sup14)C-labeled, polyethylene glycol-linked, high-molecular-weight (beta)-O-4 lignin model compound (model I) that represents the major nonphenolic structure of lignIn.
Abstract: Many ligninolytic fungi appear to lack lignin peroxidase (LiP), the enzyme generally thought to cleave the major, recalcitrant, nonphenolic structures in lignin. At least one such fungus, Ceriporiopsis subvermispora, is nevertheless able to degrade these nonphenolic structures. Experiments showed that wood block cultures and defined liquid medium cultures of C. subvermispora rapidly depolymerized and mineralized a (sup14)C-labeled, polyethylene glycol-linked, high-molecular-weight (beta)-O-4 lignin model compound (model I) that represents the major nonphenolic structure of lignin. The fungus cleaved model I between C(inf(alpha)) and C(inf(beta)) to release benzylic fragments, which were shown in isotope trapping experiments to be major products of model I metabolism. The C(inf(alpha))-C(inf(beta)) cleavage of (beta)-O-4 lignin structures to release benzylic fragments is characteristic of LiP catalysis, but assays of C. subvermispora liquid cultures that were metabolizing model I confirmed that the fungus produced no detectable LiP activity. Three results pointed, instead, to the participation of a different enzyme, manganese peroxidase (MnP), in the degradation of nonphenolic lignin structures by C. subvermispora. (i) The degradation of model I and of exhaustively methylated (nonphenolic), (sup14)C-labeled, synthetic lignin by the fungus in liquid cultures was almost completely inhibited when the Mn concentration of the medium was decreased from 35 (mu)M to approximately 5 (mu)M. (ii) The fungus degraded model I and methylated lignin significantly faster in the presence of Tween 80, a source of unsaturated fatty acids, than it did in the presence of Tween 20, which contains only saturated fatty acids. Previous work has shown that nonphenolic lignin structures are degraded during the MnP-mediated peroxidation of unsaturated lipids. (iii) In experiments with MnP, Mn(II), and unsaturated lipid in vitro, this system mimicked intact C. subvermispora cultures in that it cleaved nonphenolic (beta)-O-4 lignin model compounds between C(inf(alpha)) and C(inf(beta)) to release a benzylic fragment.

129 citations

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TL;DR: It was shown by immunogold labeling that lignin peroxidase of Phanerochaete chrysosporium is located on the surface of the wood cell wall or within areas of heavy attack, and did not diffuse into undecayed parts of the cell wall.
Abstract: The penetration of enzymes into wood cell walls during white rot decay is an open question A postembedding immunoelectron microscopic technique was the method of choice to answer that question Infiltration of pine wood specimens with a concentrated culture filtrate greatly improved the labeling density and, thereby, reproducibility Characterization of the concentrated culture filtrate by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting (immunoblotting) revealed three closely spaced proteins of molecular weights about 42,000 showing immunoreactivity against anti-lignin peroxidase serum It was shown by immunogold labeling that lignin peroxidase of Phanerochaete chrysosporium is located on the surface of the wood cell wall or within areas of heavy attack It did not diffuse into undecayed parts of the cell wall The reasons for preventing lignin peroxidase from penetrating wood cell walls during white rot decay are discussed

101 citations


Cited by
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TL;DR: The use of fungi in low cost bioremediation projects might be attractive given their lignocellulose hydrolysis enzyme machinery.

1,448 citations

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TL;DR: Actinobacteria are Gram-positive bacteria with high G+C DNA content that constitute one of the largest bacterial phyla, and they are ubiquitously distributed in both aquatic and terrestrial ecosystems.
Abstract: Actinobacteria are Gram-positive bacteria with high G+C DNA content that constitute one of the largest bacterial phyla, and they are ubiquitously distributed in both aquatic and terrestrial ecosystems. Many Actinobacteria have a mycelial lifestyle and undergo complex morphological differentiation. They also have an extensive secondary metabolism and produce about two-thirds of all naturally derived antibiotics in current clinical use, as well as many anticancer, anthelmintic, and antifungal compounds. Consequently, these bacteria are of major importance for biotechnology, medicine, and agriculture. Actinobacteria play diverse roles in their associations with various higher organisms, since their members have adopted different lifestyles, and the phylum includes pathogens (notably, species of Corynebacterium, Mycobacterium, Nocardia, Propionibacterium, and Tropheryma), soil inhabitants (e.g., Micromonospora and Streptomyces species), plant commensals (e.g., Frankia spp.), and gastrointestinal commensals (Bifidobacterium spp.). Actinobacteria also play an important role as symbionts and as pathogens in plant-associated microbial communities. This review presents an update on the biology of this important bacterial phylum.

1,199 citations

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TL;DR: In this paper, a review of the applications of laccases within different industrial fields as well as their potential extension to the nanobiotechnology area is presented, where they are also used as cleaning agents for certain water purification systems, as catalysts for the manufacture of anti-cancer drugs and even as ingredients in cosmetics.

1,131 citations

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TL;DR: The most efficient lignin degraders, estimated by 14CO2 evolution from 14C-[Ring]-labelled synthetic lign in (DHP), belong to the first group, whereas many of the most selective lignIn-degrading fungi belong toThe second, although only moderate to good [14C]DHP mineralization is obtained using fungi from this group.
Abstract: White-rot fungi produce extracellular lignin-modifying enzymes, the best characterized of which are laccase (EC 1.10.3.2), lignin peroxidases (EC 1.11.1.7) and manganese peroxidases (EC 1.11.1.7). Lignin biodegradation studies have been carried out mostly using the white-rot fungus Phanerochaete chrysosporium which produces multiple isoenzymes of lignin peroxidase and manganese peroxidase but does not produce laccase. Many other white-rot fungi produce laccase in addition to lignin and manganese peroxidases and in varying combinations. Based on the enzyme production patterns of an array of white-rot fungi, three categories of fungi are suggested: (i) lignin-manganese peroxidase group (e.g.P. chrysosporium and Phlebia radiata), (ii) manganese peroxidase-laccase group (e.g. Dichomitus squalens and Rigidoporus lignosus), and (iii) lignin peroxidase-laccase group (e.g. Phlebia ochraceofulva and Junghuhnia separabilima). The most efficient lignin degraders, estimated by 14CO2 evolution from 14C-[Ring]-labelled synthetic lignin (DHP), belong to the first group, whereas many of the most selective lignin-degrading fungi belong to the second, although only moderate to good [14C]DHP mineralization is obtained using fungi from this group. The lignin peroxidase-laccase fungi only poorly degrade [14C]DHP.

1,112 citations

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TL;DR: Broadening the knowledge of lignocellulose biodegradation processes should contribute to better control of wood-decaying fungi, as well as to the development of new biocatalysts of industrial interest based on these organisms and their enzymes.
Abstract: Wood is the main renewable material on Earth and is largely used as building material and in paper-pulp manufacturing. This review describes the composition of lignocellulosic materials, the different processes by which fungi are able to alter wood, including decay patterns caused by white, brown, and soft-rot fungi, and fungal staining of wood. The chemical, enzymatic, and molecular aspects of the fungal attack of lignin, which represents the key step in wood decay, are also discussed. Modern analytical techniques to investigate fungal degradation and modification of the lignin polymer are reviewed, as are the different oxidative enzymes (oxidoreductases) involved in lignin degradation. These include laccases, high redox potential ligninolytic peroxidases (lignin peroxidase, manganese peroxidase, and versatile peroxidase), and oxidases. Special emphasis is given to the reactions catalyzed, their synergistic action on lignin, and the structural bases for their unique catalytic properties. Broadening our knowledge of lignocellulose biodegradation processes should contribute to better control of wood-decaying fungi, as well as to the development of new biocatalysts of industrial interest based on these organisms and their enzymes. [Int Microbiol 2005; 8(3):195-204]

1,055 citations