Pulping and bleaching of CAD-deficient wood

Mutant loblolly pine trees that are deficient in the enzyme cinnamyl alcoho l dehydrogenase (CAD) have been obtained through directed breeding. The lig nin 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, th e CAD-deficient wood was much more easily delignified. In addition, the pul p 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 phe nolic content. The molecular weight of an isolated milled wood lignin from CAD-deficient pine was similar to 35% less than that from a normal pine tre e.