Potential of modified lignin for animal feed

Plant walls contain cellulose, the main component of paper and a source of
sugars for ethanol production. Cellulose could be described as the “brick” of
the cell wall, while pectin, hemicellulose and lignin function like mortar,
cementing everything together.

Lignin is vital for plant survival, but
its structure impedes cellulose conversion. But what if lignin were altered so
that it would break down easier, thus facilitating the production of paper,
ethanol and other industrial products?

That’s the goal of ARS scientists
at the U.S. Dairy Forage Research Center in Madison, Wis. There, research
agronomist John Grabber–working with ARS plant physiologist Ronald Hatfield,
Fachuang Lu of the University of Wisconsin, and John Ralph, formerly with ARS
and now at the University of Wisconsin–has designed lignin that breaks down
more easily.

Grabber and his colleagues first tested the effects of
changing the cell walls in a laboratory–before applying those changes to live
plants–by incorporating a chemical compound called coniferyl ferulate into
lignin formed within cell walls. First, they synthesized the compound in the lab
and added it to cell walls isolated from corn. Then they subjected the cell
walls to alkaline treatments, which are commonly used to degrade
lignin.

The altered lignin broke down more readily than conventional
lignin under mild alkaline conditions, demonstrating the potential for this
modification to facilitate cellulose use. Further research showed that
incorporating other molecules such as feruloyl and caffeoylquinic acid into
lignin could also enhance cellulose utilization. Hatfield, Ralph and ARS
geneticist Jane Marita at Madison are now leading efforts to engineer plants to
make lignin with coniferyl ferulate.

This work has potential benefits not
just for paper and ethanol production, but also for livestock production.
Modified lignin could make fibrous crops more digestible, allowing producers to
feed more forage crops and less grain to their
livestock.