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Biological method to pre-dry lumber with wetwood

https://library.fpinnovations.ca/en/permalink/fpipub42290
Author
Yang, D.-Q.
Date
March 2005
Material Type
Research report
Field
Wood Manufacturing & Digitalization
Author
Yang, D.-Q.
Date
March 2005
Material Type
Research report
Physical Description
44 p.
Sector
Wood Products
Field
Wood Manufacturing & Digitalization
Research Area
Advanced Wood Manufacturing
Subject
Yeasts
Wetwoods
Seasoning
Bacteria
Series Number
General Revenue 4030
Location
Sainte-Foy, Québec
Language
English
Abstract
Wetwood, or water pocket, has higher moisture content and lower permeability than normal wood, which cause serious problems for lumber drying. The high moisture content of wetwood usually requires relatively long periods for adequate drying; consequently, it causes a high risk for developing checks, splits, crook, bow and twist of lumber in kiln drying. These problems have not been solved by any physical, chemical or mechanical methods yet. Using biological method to pre-dry lumber containing wetwood is a new concept introduced in this project. Wetwood is formed by bacteria growth inside normal wood. Some fungi are able to kill bacteria and to utilize foetid liquid produced by these micro-organisms. Consequently, the permeability of wetwood can be increased and the lumber drying rate can be improved. The present project intends a research on biological method to pre-dry lumber containing wetwood, and to evaluate efficacy and economic benefit of such a biological treatment. Trees of balsam fir, sub-alpine fir and aspen were felled and cut into lumber. Isolation of causal agents was conducted from wet pockets of these wood species by using peptone agar and malt extract agar media. A total of 319 cultures were obtained from the wetwood of these three wood species. Three bacteria and two yeasts were isolated from balsam fir wetwood, 2 bacteria and 1 yeast were more frequently isolated from aspen wetwood, and 2 bacteria and 5 yeasts were obtained from sub-alpine fir. Two bacteria were isolated from the wetwood of all 3 wood species: Shigella sonnei and Pseudomonas fluorescens. Other bacteria and yeasts isolated were identified as Aerococcus viridans, Chryseomonas luteol, Candida boidinli, C. zeylanoides, Cryptococcus albidus, C. laurentii, C. terreus, and Rhodotorula mucileginosa. In addition to these identified bacteria and yeasts, two other yeasts isolated from balsam fir and sub-alpine fir wetwood were unabile to be identified. Six bacteria and yeast isolates were re-inoculated on normal wood of balsam fir; they were A-a (a bacterium isolated from aspen and identified as Shigella sonnei), A-c (a yeast isolated from aspen and identified as Cryptococcus laurentii), B-a (a bacterium isolated from balsam fir and identified as Shigella sonnei), B-c (a mixture of 2 bacteria isolated from balsam fir and identified as Shigella sonnei and Aerococcus viridans), Y-2 (an unidentified yeast isolated from balsam fir), and SaB-2 (a bacterium isolated from sub-alpine fir and identified as Shigella sonnei). The result showed that all of these micro-organisms caused wetwood formation on inoculated normal wood samples in 2 weeks. This result indicates that wetwood formation in trees is not caused by only 1 micro-organism but is more likely caused by several species (either bacteria or yeasts) that can colonise well in the wood of trees. The moisture contents (MC) of the inoculated wood blocks increased from 41.2% to 220-240 %, whereas the MCs of the control samples submerged in a liquid culture medium without inoculation reached only 110%. When control samples were dried to a MC of 13%, the inoculated wood samples still had MCs between 80% and 105%. This result indicates that drying lumber containing wetwood will take double the time required to dry normal lumber without wetwood. An antagonist test using fungal candidates was conducted on agar plates. In this test, 6 potential fungal antagonists and 6 wetwood causal agents (WCA) were used. The six fungal antagonists were Gliocladium roseum (Forintek bioprotectant), a white isolate of Ophiostoma piliferum (Cartapip), a white isolate of Ceratocystis resinifera (an anti-sapstain biological agent produced by Chantal Morin at Laval University), Oidium sp.A (a white fungus in Deuteromycetes isolated from Jack pine logs, DP3/5B-3a, 1998), Oidium sp. B (a white fungus in Deuteromycetes isolated from balsam fir logs, DF3/1B-1b, 1998), and Phaeotheca dimorphospora (a biological control agent of tree disease from Laval University). The six wetwood causal agents were A-a (a bacterium isolated from wetwood of aspen), A-c (a yeast isolated from wetwood of aspen), B-a (a bacterium isolated from wetwood of balsam fir), Y-2 (a yeast isolated from wetwood of balsam fir), SaB-2 (a bacterium isolated from wetwood of sub-alpine fir), and SaY-4 (a mixture of a yeast and a bacterium isolated from wetwood of sub-alpine fir). The results showed that Oidium sp.A and Oidium sp.B were the most effective against all 6 WCA inoculated; they reduced growth of the WCA in 7 days and completely absorbed colonies of WCA in 11 days. G. roseum, O. piliferum, and C. resinifera were moderately effective against 5 WCAs, but not effective on bacterium A-a that was isolated from aspen wetwood. P. dimorphospora was the least effective against any of these WCA. The three promising fungal antagonists, Oidium sp., G. roseum and the white isolate of O. piliferum, selected from agar plate test were used for a following antagonist test on balsam fir wetwood blocks in the laboratory conditions. This test was conducted on small wetwood samples (2 x 4 x 1 inch) in incubators at 25°C and two relative humidity ranges (100% and 75% RH). The results showed that all these three fungi were able to establish on wood surfaces and able to reduce wetwood contents. At 25°C and 75% RH, Oidium sp. was the most effective to reduce wetwood content in samples, followed by G. roseum, and then by O. piliferum. G. roseum and Oidium sp. not only reduce wetwood content, but also inhibit mold growth and wood stain, compared with untreated control samples. At 25°C and 100% RH, the moisture contents of treated and untreated samples were not changed in any week of the testing period. This result indicates that biological pre-dry wetwood samples should not be conducted at this high relative humidity condition. A test was conducted to investigate the ability of Oidium sp., the wetwood control candidate, against sapstaining fungi on wood. The results showed that if balsam fir wood wafers were inoculated with Oidium sp. 3 days before the staining fungi, no staining fungi grew on these samples. If wood wafers were inoculated with Oidium sp. and staining fungi at the same time, samples were covered by both Oidium sp. and the staining fungus Ophiostoma piceae in a ratio of 50 to 50%. If wood wafers were inoculated with the staining fungi 3 days before Oidium sp., samples were absolutely covered by the staining fungus and fully stained.
Wetwood
Seasoning - Predrying
Yeasts
Bacteria
Biological Control
Fungi
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