Search

The depletion of root-available Ca in northern forest soils exposed to decades of increased acid deposition adversely affects forest health and productivity. Laboratory studies indicated the potential of wood-decay fungi to restore lost Ca. This study presents changes in concentration of Ca, Mg, and K in sapwood of red spruce (Picea rubens Sarg.), red maple (Acer rubrum L.), eastern hemlock (Tsuga canadensis (L.) Carriere), and paper birch (Betula papyrifera Marshall) during the decay process at two experimental forests for 12 years and to compare concentrations of exchangeable Ca, Mg, and Al in decayed wood residues at 10 and 12 years with those in the forest floor. Significant loss of mass indicated by decreasing wood density occurred after 2-8 years in conifers and after only 2 years in hardwoods. A significant gain in wood K was observed at 2 years followed by a significant loss at 8 years. A negligible gain in Ca concentration occurred at 2 years and a substantial gain at 8 years. Observed changes in Mg concentration were variable. No significant difference in exchangeable Ca concentration was observed between decayed wood residue of spruce and maple and the forest floor. However, decayed wood residue had a much lower Al concentration and molar Al/Ca ratio, a condition characteristic of sites with high root-available Ca. Resume: La diminution du Ca disponible pour les racines dans les sols des forets nordiques exposees a plusieurs decennies de depots acides accrus affecte la sante et la productivite de la foret. Des etudes en laboratoire ont montre que les champignons de carie du bois avaient la capacite de restaurer le Ca perdu. Cette etude presente l'evolution de la concentration de Ca, Mg et K dans le bois d'aubier de l'epinette rouge (Picea rubens Sarg.), de l'erable rouge (Acer rubrum L.), de la pruche du Canada (Tsuga canadensis (L.) Carriere) et du bouleau a papier (Betula papyrifera Marshall) durant le processus de decomposition dans deux forets experimentales pendant 12 ans et compare les concentrations de Ca, Mg et Al echangeables dans les debris ligneux apres 10 et 12 ans a celles qu'on retrouve dans la couverture morte. Une perte importante de masse, comme le revele la diminution de la densite du bois, est survenue apres 2 a 8 ans chez les coniferes et apres seulement deux ans chez les feuillus. Un gain important en K dans le bois a ete observe apres 2 ans suivi par une perte importante apres 8 ans. Un gain negligeable dans la concentration de Ca est survenu apres 2 ans suivi d'un gain substantiel apres 8 ans. Les changements observes dans la concentration de Mg etaient variables. Aucune difference significative n'a ete observee dans la concentration de Ca echangeable entre les debris ligneux caries d'epinette, d'erable et la couverture morte. Cependant, les debris ligneux caries avaient une concentration en Al et un rapport molaire Al/Ca beaucoup plus faibles, une situation caracteristique des stations ou la disponibilite de Ca pour les racines est elevee. [Traduit par la Redaction], Introduction Calcium is the fifth most abundant element in the earth's crust. Other than N, Ca is considered the most important essential mineral for managing plant diseases (Rahman and Punja [...]

Abstract: The decay of coarse woody debris is a key component in the formation of forest soil and in the biogeochemical cycles of Ca and Mg. We tracked changes in [...]

Researchers were able to detect brown-rot and white-rot basidiomycetes in wood using the primer pair ITS1-F AND ITS4 to amplify fungal DNA using the polymerase chain reaction. The fungi could be detected before there was measurable loss of wood. Restriction fragment length polymorphisms of the internal transcribed spacer region were used to identify the fungi down to the species level.

Brown rot (BR) decay mechanisms employ carbohydrate-active enzymes (CAZymes) as well as a unique non-enzymatic chelator-mediated Fenton (CMF) chemistry to deconstruct lignocellulosic materials. Unlike white rot fungi, BR fungi lack peroxidases for lignin deconstruction, and also lack some endoglucanase/cellobiohydrolase activities. The role that the CMF mechanism plays in "opening up" the wood cell wall structure in advance of enzymatic action, and any interaction between CMF constituents and the selective CAZyme suite that BRs possess, is still unclear. Expression patterns for CMF redox metabolites and lytic polysaccharide monooxygenase (LPMO–AA9 family) genes showed that some LPMO isozymes were upregulated with genes associated with CMF at early stages of brown rot by Gloeophyllum trabeum. In the structural studies, wood decayed by the G. trabeum was compared to CMF-treated wood, or CMF-treated wood followed by treatment with either the early-upregulated LPMO or a commercial CAZyme cocktail. Structural modification of decayed/treated wood was characterized using small angle neutron scattering. CMF treatment produced neutron scattering patterns similar to that of the BR decay indicating that both systems enlarged the nanopore structure of wood cell walls to permit enzyme access. Enzymatic deconstruction of cellulose or lignin in raw wood samples was not achieved via CAZyme cocktail or LPMO enzyme action alone. CMF treatment resulted in depolymerization of crystalline cellulose as attack progressed from the outer regions of individual crystallites. Multiple pulses of CMF treatment on raw wood showed a progressive increase in the spacing between the cellulose elementary fibrils (EFs), indicating the CMF eroded the matrix outside the EF bundles, leading to less tightly packed EFs. Peracetic acid delignification treatment enhanced subsequent CMF treatment effects, and allowed both enzyme systems to further increase spacing of the EFs. Moreover, even after a single pulse of CMF treatment, both enzymes were apparently able to penetrate the cell wall to further increase EF spacing. The data suggest the potential for the early-upregulated LPMO enzyme to work in association with CMF chemistry, suggesting that G. trabeum may have adopted mechanisms to integrate non-enzymatic and enzymatic chemistries together during early stages of brown rot decay. [ABSTRACT FROM AUTHOR]

Brown rot fungi were incubated in agar and agar-wood microcosms containing metallic or hydroxide forms of AI, Cu, and Fe. Metal dissociation was associated with elevated oxalate concentrations in agar, but metals translocated into wood did not affect oxalate accumulation, crystal production, or decay rate, thus showing a substrate-dependent oxalate dynamic.

As one of the most abundant materials in nature, lignin has been used widely in co-generation operations and for fine chemicals and bio-fuels production. These uses, although important, are of relatively low value. Lignin contains many aromatic compounds with useful structures, and it is potentially more profitable to produce high-value fine chemicals from the low-molecular weight lignin fraction while using the high-molecular weight fraction for fuel or other applications. A transgenic P. putida bacterial strain PDHV85 was developed with the capability to convert vanillin, vanillic acid, and syringaldehyde to 2-pyrone-4,6-dicarboxylic acid (PDC), a novel platform chemical that can produce a variety of bio-based polymers. Initial testing with vanillin showed promise for lignin conversion. Testing for this, we used kraft lignin, Japanese cedar (Cryptomeria japonica), or birch (Betula platyphylla) to represent some of the most abundant industrial lignin sources from softwood and hardwood. Repeated manipulation of culture conditions and strain adaptation allowed conversion of these extracts to PDC by PDHV85, which has not previously been reported in a bacterial strain. No inhibition was observed at 0.14 mg/mL kraft lignin extract, 1.14 mg/mL Japanese cedar extract, nor 1.15 mg/mL birch extract when using the optimized growth conditions. [ABSTRACT FROM AUTHOR]