Treesearch

In this work, the source of extracellular hydrogen peroxide in cultures of Ceriporiopsis subvermispora was investigated. A thorough search for the presence in the growth medium of oxidases known to be produced by other fungi gave negative results. We therefore explored the prospect that H2O2 might arise from the oxidation of organic acids by MnP. Both oxalate and glyoxylate were found in the extracellular fluid of C. subvermispora grown in salt medium, at concentrations of 2.5 and 0.24 mM, respectively. MnP titers correlated with the mineralization of [14 C]-oxalate in cultures maintained...

We describe here recent methods for quantitative assessment of specific P. chrysosporium mRNAs in organopollutant contaminated soils and in Aspen wood chips. Magnetic capture techniques were used to rapidly purify poly(A)-RNA, and quantitative RT-PCR protocols were developed for all known lignin peroxidase (lip) and cellobiohydrolase (cbh1) genes. The methodology is extremely sensitive and highly specific. Results indicated that gene transcript patterns varied dramatically in response to substrate. In general, transcript patterns in defined media were unreliable predictors of expression in...

The kinetics of Mn3+- oxalate formation and decay were investigated in reactions catalyzed by manganese peroxidase (MnP) from the basiomycete Ceriporiopsis subvermispora in the absence of externally added hydrogen peroxide. A characteristic lag observed in the formation of this complex was shortened by glyoxylate or catalytic amounts of Mn3+ or hydrogen peroxide. MnP titers had a minor effect on this lag and did not influence the decay rate of the complex. In contrast, Mn2+ and oxalate drastically affected maximal concentrations of the Mn3+- oxalate complex formed, the decay of which was...

One-part polyurethane wood adhesives comprise a new class of general purpose consumer products. Manufacturersa claims of waterproof bonds brought many inquiries to the Forest Products Laboratory (FPL) from users constructing aircraft, boats, lawn furniture, and other laminated materials for outdoor use. Although FPL has technical information on several types of polyurethane and isocyanate-based adhesives for wood, no information was available on this new class of adhesives. Four commercial polyurethane adhesives, along with a resorcinol-formaldehyde adhesive to represent a standard of...

As part of international efforts to evaluate alternative reaction-to-fire tests, several series of room/comer tests have been conducted. This paper reviews the overall results of related projects in which different test protocols for standard room/corner tests were used. Differences in the test protocols involved two options for the ignition burner scenario and whether the ceiling was also lined with the test materials. The test materials were placed on three walls of the room in all the tests. The two burner scenarios were (1) 40 kW for 300 s followed by 160 kW for 300 s and (2) 100 kW...

Finely divided aspen and spruce woods and a high lignin pine kraft pulp have been selectively delignified to low lignin levels using aqueous solutions of polyoxometalates under anaerobic conditions. The reduced polyoxometalates in the solutions can be reoxidized with oxygen and act as wet oxidation catalysts for the mineralization of the solubilized lignin and carbohydrate fragments to carbon dioxide and water.

Wood may be described as an orthotropic material with unique and independent mechanical properties in the directions of three mutually perpendicular axes– longitudinal ( L ), radial ( R ), and tangential (T ). These mechanical properties are also called engineering constants. Orthotropic materials are of special relevance to composite materials. Therefore, mathematical relations and experimental procedures for engineering constants of orthotropic composites can be conveniently applied to wood when considered as an engineering material. In this paper, we present how variation of shear...

Brightness, strength, economy, and paper machine runnability are common concerns of pacemakers who use virgin or recycled fiber furnishes. Fiber loadining, a process that precipitates calcium carbonate partially inside the fiber lumen, is a cost-effective technology that could substantially upgrade mechanical pulp furnishes. This study demonstrates the optical and physical handsheet property advantages of fiber loading typical newsprint and thermomechanical pulp (TMP) furnishes. Inclusion of hydrogen peroxide during fiber loading prevented the expected alkaline darkening. Moreover, brief...

In 1991, the USDA Forest Service, Forest Products Laboratory (FPL) and the Federal Highway Administration (FHWA) formed a joint cooperative research program for wood transportation structures. Development and execution of this program was based on a national assessment of research needs and priorities. In the 5 years since completion of the research needs assessment, significant research has been completed or is ongoing for wood transportation structures. This publication provides a summary of the research accomplishments of the joint FPL1FHWA research program for wood transportation...

A density-dependent matrix growth model of uneven-aged loblolly pine stands was developed with data from 991 permanent plots in the southern United States. The model predicts the number of pine, soft hardwood, and hard hardwood trees in 13 diameter classes, based on equations for ingrowth, upgrowth, and mortality. Projections of 6 to 10 years agreed with the growth of stands between the last two inventories. In 300-year simulations of undisturbed growth, softwood species were replaced by hardwoods, in accord with previous knowledge. Soft hardwood species became dominant on good sites and...