Gene-altered wood may yield more paper.

It's not pulp fiction. Wood harvested from genetically engineered trees might make paper and some fuels easier and less costly to produce.

A team of researchers has genetically engineered aspens to reduce their content of lignin, a tough polymer that glues together the cells in trees and that the papermaking process must chemically extract. What's more, the engineered trees actually grow faster and have a higher proportion of cellulose, the raw material for paper, than normal aspens do.

Vincent L. Chiang of the Michigan Technological University in Houghton and his colleagues targeted a gene that the aspen uses in lignin biosynthesis. By blocking this gene with so-called antisense molecules (SN: 2/16/91, p. 108), the researchers cut lignin production in half.

The paper industry "spends a lot of time thinking about sustainability," says Kenneth Munson, director of forest research and biotechnology at the International Paper Co. in Dallas. "Anything that can be done to make lignin easier to extract or to have less of it to extract will have some very important implications" by lowering energy costs and the amount of chemicals used.

Other groups have successfully reduced the lignin content of tobacco and the much-studied laboratory plant Arabidopsis, but those attempts softened the cell walls and stunted the growth of the plants.

In the current study on aspens, a 15 percent increase in cellulose accompanied the drop in lignin, providing enough plant material to maintain the trees' structural integrity. The ratio of cellulose to lignin in the genetically engineered aspens is twice the ratio in the normal tree. Chiang and his colleagues describe their work in the August NATURE BIOTECHNOLOGY.

The shift from lignin to cellulose production is not unexpected, says Tom Jeffries, director of the Department of Agriculture Forest Service's Forest Products Laboratory in Madison, Wis. However, "the most shocking thing was the sustained growth of the plants," he adds. "The [engineered] plants were a good 25 to 30 percent taller." Chiang speculates that blocking the lignin gene changes other compounds that stimulate growth of the tree.

Cutting the lignin content of trees could also make it more practical to produce ethanol and other biofuels from wood, says Jeffries. Oil companies add ethanol, usually fermented from corn, to gasoline to help it burn cleanly.

Chiang says he chose aspens to study because they grow fast and are popular in the Great Lakes region for wood pulping. He and his colleagues are now testing their methods in trees used worldwide, such as eucalyptus.