Pulping and Bleaching of Partially Cad-Deficient Wood

Abstract

Mutant loblolly pine trees that are partially deficient in cinnamyl alcohol dehydrogenase (CAD) have been studied as a possible new source of pulpwood. Young (4-and 6-year-old) partially CAD-deficient pine trees are -20% more easily delignified (pulping and bleaching) and provide similar pulp yields to that of similarly aged normal pines grown on the same plots. Bleached pulp from a 6year-old partially CAD-deficient pine tree displayed better strength properties than the same age normal pine tree; this probably reflects the milder pulping conditions needed in the case of the partially CAD-deficient tree. Studies also were conducted on a limited number of 14-year-old trees from a different genetic background. In contrast to the results with young trees, no real differences in ease of delignification, pulp yields, bleached pulp strength properties, and wood specific gravities were observed with the 14-year-old trees. There would likely be no penalty if partially CAD-deficient trees were used for lumber products. The rapid growth of partially CAD-deficient trees could make them a valuable pulpwood.

A sequence mutation in the cinnamyl alcohol dehydrogenase gene associated with altered lignification in loblolly pine

“…In addition to lignin composition changes, the cad‐n1 allele appears to be associated with increased stem‐growth traits in heterozygous trees (Wu et al ., 1999). This growth promotion correlates to an increase in the debarked volume of 4‐year‐old trees (14%) (Wu et al ., 1999) that is also observed in 14‐year‐old trees (Dimmel et al ., 2002). A possible explanation could be that trees harbouring the cad‐n1 allele may invest fewer resources into the production of monolignols, allowing reallocation of resources towards growth.…”

“…In totally CAD‐deficient trees ( cad‐n1/cad‐n1 ), delignification was significantly easier but the pulp yields were relatively low (∼33%) compared to normal trees (48%) (Dimmel et al ., 2001). In 4–6‐year‐old partially CAD‐deficient trees (heterozygous) delignification increased in efficiency by ∼20% and yields were similar to the wild‐type (Dimmel et al ., 2002). In contrast to these younger trees, a small sample of 14‐year‐old partially CAD‐deficient trees displayed no major differences in ease of delignification and pulp yield (Dimmel et al ., 2002).…”

“…In 4–6‐year‐old partially CAD‐deficient trees (heterozygous) delignification increased in efficiency by ∼20% and yields were similar to the wild‐type (Dimmel et al ., 2002). In contrast to these younger trees, a small sample of 14‐year‐old partially CAD‐deficient trees displayed no major differences in ease of delignification and pulp yield (Dimmel et al ., 2002).…”

Impact of Lignin and Carbohydrate Chemical Structures on Degradation Reactions during Hardwood Kraft Pulping Processes

“…A more suitable native lignin may allow for a reduced alkali charge, lower cooking temperature, and/or decreased retention time. As these conditions result in milder cooking conditions, an increase in pulp yield and fiber quality may be expected (Dimmel et al 2001(Dimmel et al , 2002.…”

Association of the cad-n1 allele with increased stem growth and wood density in full-sib families of loblolly pine

“…In addition, significantly less energy was required (15 to 25% lower H-factor) to pulp to a given kappa number than for wild-type trees and the pulp of the heterozygotes was brighter and stronger [2]. On the contrary, Dimmel et al [3] found no apparent differences in ease of delignification or pulp yield between heterozygous and wild-type trees that were 14 years old. In a much larger sample, effects associated with this cad-n1 allele were found by comparing wood density and growth traits of cad-n1 heterozygous trees with wild-type trees in a 10-year-old open-pollinated family experimentally growing under two levels of fertilization.…”