Treesearch

We changed the fluxes of xylose metabolites in recombinant Saccharomyces cerevisiae by manipulating expression of Pichia stipitis genes(XYL1 and XYL2) coding for xylose reductase (XR) and xylitol dehydrogenase (XDH), respectively. XYL1 copy number was kept constant by integrating it into the chromosome. Copy numbers of XYL2 were varied either by integrating XYL2 into the chromosome or by transforming cells with XYL2 in a multicopy vector. Genes in all three constructs were under control of the strong constitutive glyceraldehyde-3-phosphate dehydrogenase promoter. Enzymatic activity of XR...

Candida boidinii produces significant amounts of xylitol from xylose, and assays of crude homogenates for aldose (xylose) reductase (XYL1p) have been reported to show relatively high activity with NADH as a cofactor even though XYL1p purified from this yeast does not have such activity. A gene coding for XYL1p from C. boidinii (CbXYL1) was isolated by amplifying the central region using primers to conserved domains and by genome walking. CbXYL1 has an open reading frame of 966 bp encoding 321 amino acids. The C. boidinii XYL1p is highly similar to other known yeast aldose reductases and is...

The purpose of this work was to evaluate the effects of a new boron-nitrogen, phosphate-free fire-rerardant (FR) formulation on the initial strength of No. 1 southern pine 2 by 4 lumber and its potential for in-service thermal degradation. The lumber was evaluated according to Method C of the D 5664 standard test method. The results indicated that for lumber exposed at 150°F (66°C) for 108 days, FR treatment and redrying significantly (a £ 0.10) decreased initial bending strength by about 13%compared to that of untreated controls. No significant difference occurred in the rate of strength...

Heat sterilization is often required to prevent spread of insects and pathogens in wood products in international trade. Heat sterilization requires estimating the time necessary for the center of the wood configuration to reach the temperature required to kill insects or pathogens. In these experiments on 1.0- and 1.8-in.- (25- and 46-mm-) thick slash pine, heating time at 160°F(71°C) increased exponentially with increase in wet bulb depression. The time required for the center of green 1.0-in.- (25-mm-) thick boards to reach 133°F (56°C) vaned from 15 min at a low wet bulb depression...

The objective of this work was to evaluate the effects of a new boron-nitrogen, phosphate-free fire-retardant (FR) formulation on several mechanical properties of FR-treated wood and to assess the potential of this treatment for in-service thermal-induced strength loss resulting from exposure to high temperature. Fire-retardant-treated and untreated small clear specimens were cut from three wood species, Douglas-fir, southern pine, and white spruce, according to ASTM D 5664-95 and evaluated in bending and tension. compression, and shear parallel to grain. Evaluations were conducted before...

The objective of this work was to evaluate (a) the effects of a new boron– nitrogen, phosphate-free fire-retardant (FR) formulation on the initial strength of Douglas-fir AB-grade plywood and (b) the potential of this FR treatment to experience subsequent thermal degradation In-service when exposed to elevated temperatures. Test Method ASTM D 5516 was generally followed The results of our analysis indicated that treatment and post- treatment redrying with the new boron-nitrogen, phosphate-free FR had a significant negative effect of about 7% on bending strength and a significant negative...

Pesticide entrainment in stormwater runoff can contribute to non-point source pollution of surface waters. Granular activated carbon has been successfully used for removing pesticides from wastewater. However, implementation of granular activated carbon sorption media in stormwater filtration systems comes with high initial capital investment and operating costs. Modified pine barks offer attractive alternative sorption media for use in stormwater filtration systems. Pine barks constitute a significant fraction of underutilized low-value waste materials from the forest products industry....

When wood is exposed to various environmental conditions, many degradation reactions (biological, ultraviolet, mechanical, moisture, and chemical) can occur. To protect wood from biological degradation, chemical preservatives are applied by nonpressure or pressure treatment. Penetration and retention of a chemical depend upon the wood species and the amount of heartwood (more difficult to treat) or sapwood (easier to treat). The objective of adding preservatives is to achieve long-term effectiveness for the wood product, thus sequestering (capturing and storing) carbon.

The increase in the use of non-arsenical copper-based wood preservatives in response to environmental concerns has been accompanied by interest in copper-tolerant decay fungi. Oxalic acid production by brown-rot fungi has been proposed as one mechanism of copper tolerance. Fifteen brown-rot fungi representing the genera Postia, Wolfiporia, Meruliporia, Gloeophyllum, Laetiporus, Coniophora, Antrodia, Serpula, and Tyromyces were evaluated for oxalic acid production bi-weekly in southern yellow pine (SYP) blocks treated with 1.2% ammoniacal copper citrate (CC). Eleven fungi were designated...

Accumulation of oxalic acid (OA) by brown-rot fungi and precipitation of copper oxalate crystals in wood decayed by copper-tolerant decay fungi has implicated OA in the mechanism of copper tolerance. Understanding the role of OA in copper tolerance is important due to an increasing reliance on copper-based wood preservatives. In this study, four copper-tolerant brown- rot fungi were evaluated for decay capacity and OA production in early stages of exposure to four waterborne copper-based wood preservatives (ammonical copper quat type B and D, ammonical copper citrate, and chromated copper...