Mutant loblolly pine trees that are deficient in the enzyme cinnamyl alcohol dehydrogenase (CAD) have been obtained through directed breeding. The lignin in the wood of CAD-deficient trees has a different pool of precursors, resulting in high levels of pulping-resistant C-5 linkages. Wood from a 12-year-old CAD-deficient tree has been pulped under soda and kraft conditions in microdigestors. In comparison to a normal 12-year-old loblolly pine, the CAD-deficient wood was much more easily delignified. In addition, the pulp from CAD-deficient wood was as easy to bleach as a control pulp. The high reactivity of CAD-deficient wood may be related to the lignin size and phenolic content. The molecular weight of an isolated milled wood lignin from CAD-deficient pine was ∼35% less than that from a normal pine tree.

CAD-deficient loblolly pine trees are easier to pulp and bleach, with lignin size and phenolic content contributing to their high reactivity.

PULPING AND BLEACHING OF CAD-DEFICIENT WOOD

Key Takeaway: CAD-deficient loblolly pine trees are easier to pulp and bleach, with lignin size and phenolic content contributing to their high reactivity.