Changes in Molecular Size Distribution of Cellulose during Attack by White Rot and Brown Rot Fungi

Kleman-Leyer, Karen; Agosín, Eduardo; Conner, Anthony H.; Kirk, T. Kent

doi:10.1128/aem.58.4.1266-1270.1992

Cited by 109 publications

(38 citation statements)

References 12 publications

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“…The early observations of Puls and Wood (129) have been further elaborated by other authors who have demonstrated that the in vivo mechanism of cellulose degradation differs fundamentally among wood-degrading fungi and, consequently, results in different modes of decay (78). These and other authors (79,159) have also shown that recombinant cellulase monocompents (both endoglucanases and cellobiohydrolases) effectively reduce the DP of different purified cellulose substrates by various mechanisms (79,159), suggesting that depolymerization was largely a function of the nature of the cellulosic substrate being attacked.…”

Section: Substrate Factors Limiting Hydrolysismentioning

confidence: 87%

Substrate and Enzyme Characteristics that Limit Cellulose Hydrolysis

Mansfield

Mooney

Saddler

1999

Biotechnology Progress

759

509

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The ability and, consequently, the limitations of various microbial enzyme systems to completely hydrolyze the structural polysaccharides of plant cell walls has been the focus of an enormous amount of research over the years. As more and more of these extracellular enzymatic systems are being identified and characterized, clear similarities and differences are being elucidated. Although much has been learned concerning the structures, kinetics, catalytic action, and interactions of enzymes and their substrates, no single mechanism of total lignocellulosic saccharification has been established. The heterogeneous nature of the supramolecular structures of naturally occurring lignocellulosic matrices make it difficult to fully understand the interactions that occur between enzyme complexes and these substrates. However, it is apparent that the efficacy of enzymatic complexes to hydrolyze these substrates is inextricably linked to the innate structural characteristics of the substrate and/or the modifications that occur as saccharification proceeds. This present review is not intended to conclusively answer what factors control polysaccharide biodegradation, but to serve as an overview illustrating some of the potential enzymatic and structural limitations that invariably influence the complete hydrolysis of lignocellulosic polysaccharides. IntroductionDespite the extensive amount of research undertaken over the last few decades, our understanding of how enzymes completely hydrolyze lignocellulosic substrates is still far from comprehensive or complete. Past work has indicated the complexity of the substrate and the need for many different enzymes before these substrates can be effectively and completely hydrolyzed. However, the deceptive simplicity of the repeating -1-4 linking cellobiose unit is not indicative of the complex arrangement of the substrate at the fibril, fiber, and wood/pulp levels. Similarly, although tools such as molecular biology and protein engineering have helped elucidate the role of some of the enzymes in the synergistic attack of lignocellulosic substrates, our understanding of basic mechanisms such as enzyme regulation, kinetics, and the extent of true synergism is still lacking. As a result, an important aspect of much of the research to date has been to ascertain the limiting factors involved in the decreased hydrolysis rate as time progresses. These factors have traditionally been divided into two groups: those which relate to the structure of the substrate and those related to the mechanisms and interactions of the cellulase enzymes.Various model cellulose substrates have been used for the purpose of studying the mechanism of action and interaction of individual cellulase enzymes and the effect of substrate characteristics, such as degree of polymerization and crystallinity, on the rate and efficiency of enzymatic hydrolysis. These include Avicel, solka floc, filter paper, cotton, valonia cellulose, phosphoric acid swollen cellulose, bacterial microcrystalline cellulose (BMCC) and solu...

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Section: Substrate Factors Limiting Hydrolysismentioning

confidence: 87%

Substrate and Enzyme Characteristics that Limit Cellulose Hydrolysis

Mansfield

Mooney

Saddler

1999

Biotechnology Progress

759

509

View full text Add to dashboard Cite

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“…During TFA hydrolysis amorphous (noncrystalline) cellulose is degraded, and constituents of the walls of microbial cells are hydrolysed, releasing a suite of hexose and pentoses. This hydrolysis is mimicked by the brown-rot fungi in their ability to differentiate between amorphous and crystalline cellulose (Kleman-Leyer et al, 1992). The larger concentration of carbohydrate-C extracted by TFA in the grassland and ash profiles compared with the spruce profile suggests a difference in litter quality, rate and extent of decomposition.…”

Section: Discussionmentioning

confidence: 99%

Phenolic and carbohydrate signatures of organic matter in soils developed under grass and forest plantations following changes in land use

Sanger

Anderson

Little

et al. 1997

European J Soil Science

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Comparisons were made between the phenolic and carbohydrate signatures of soil profiles developed under grass, spruce and ash stands. Samples were collected from a brown earth soil which was originally under the same land use, but over the past 43 years has supported different monocultures. Distinct signatures associated with each litter type were recorded in individual profiles. A relatively undecomposed phenolic fraction from lignin and hydrolysable carbohydrate fraction from plants had accumulated in the soils under spruce and ash. This largely reflected the quantity and quality of the litter inputs from the spruce and ash compared with the grass. The phenolic and hydrolysable carbohydrate fractions accounted for as much as 60% of the total organic carbon concentration in the deep horizons. In the grassland profile both fractions were more decomposed than under ash and spruce suggesting that the forest profiles had rapidly accumulated a carbon pool with a comparatively slow rate of decomposition. This was most apparent from the spruce profile (which contained 398 mg g-' C carbohydrate hydrolysed using trifluoracetic acid (TFA) in the C horizon compared with 165 and 45 mg g-' C under ash and grass respectively). We conclude that the decay rate of these fractions is a function of the vegetation type.

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“…Analysis of the recovered cellulose by viscosimetry and by GPC after derivatization showed that both G. trabeum and P. placenta were clearly cellulolytic in these cultures ( Table 1). The depolymerization rates were somewhat slower than the rate reported earlier for P. placenta grown on cellulose in the presence of wood [28], but they were su⁄cient to undertake a search for ROS that could contribute to cellulose degradation.…”

Section: Cellulose Cleavagementioning

confidence: 68%

Significant levels of extracellular reactive oxygen species produced by brown rot basidiomycetes on cellulose

et al. 2002

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It is often proposed that brown rot basidiomycetes use extracellular reactive oxygen species (ROS) to accomplish the initial depolymerization of cellulose in wood, but little evidence has been presented to show that the fungi produce these oxidants in physiologically relevant quantities. We used [ 14 C]phenethyl polyacrylate as a radical trap to estimate extracellular ROS production by two brown rot fungi, Gloeophyllum trabeum and Postia placenta, that were degrading cellulose. Both fungi oxidized aromatic rings on the trap to give monohydroxylated and more polar products in signi¢cant yields. All of the cultures contained 2,5-dimethoxyhydroquinone, a fungal metabolite that has been shown to drive Fenton chemistry in vitro. These results show that extracellular ROS occur at signi¢cant levels in cellulose colonized by brown rot fungi, and suggest that hydroquinone-driven ROS production may contribute to decay by diverse brown rot species.

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Changes in Molecular Size Distribution of Cellulose during Attack by White Rot and Brown Rot Fungi

Cited by 109 publications

References 12 publications

Substrate and Enzyme Characteristics that Limit Cellulose Hydrolysis

Substrate and Enzyme Characteristics that Limit Cellulose Hydrolysis

Phenolic and carbohydrate signatures of organic matter in soils developed under grass and forest plantations following changes in land use

Significant levels of extracellular reactive oxygen species produced by brown rot basidiomycetes on cellulose

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