Engineered Poplar with Altered Lignin Composition More Readily Converted to Bioproducts

The Science

A key obstacle to extracting sugars from plant biomass is the presence of the complex polymer lignin, a major component of plant cell walls that provides structural integrity and is most resistant to deconstruction. Great Lakes Bioenergy Research Center (GLBRC) researchers have mobilized the flexible nature of lignin formation in plants to produce a transgenic poplar tree that diverts carbon away from lignin formation and toward the synthesis of naringenin or p-hydroxybenzoate, which are platform chemicals and precursors to high-value products currently derived from petroleum. Without adversely affecting overall yield, the resulting poplar wood is easier to deconstruct and therefore produces higher sugar yields.

The Impact

This work demonstrates that bioenergy crop engineering can improve the efficiency of industrial biomass deconstruction by introducing “zips,” or weak bonds, into the lignin polymer. The resulting “zip-lignin” is easier to degrade and contains soluble dihydroxybenzoate (DHB) which has potential to become a valuable coproduct in biorefineries.

Summary

Researchers harnessed the flexibility of the lignin biosynthesis pathway to engineer bioenergy crops that are more valuable and less expensive to break down. Their approach involved transforming a hybrid poplar with the 3-dehydroshikimate dehydratase gene (QsuB) which has shown the potential to divert carbon away from the lignin biosynthesis pathway and toward soluble dihydroxybenzoate (DHB), a platform chemical and precursor to high value products like plastics. The resulting transgenic poplar wood contained up to 33% less lignin and demonstrated improved saccharification, releasing up to 40% more glucose than the untransformed hybrid poplar. The transgenic poplar also displayed novel incorporation of DHB into the lignin backbone, which introduced weaker bonds, or “zips,” into the polymer.

Principal Investigator

Shawn D. Mansfield
University of British Columbia
[email protected]

BER Program Manager

U.S. Department of Energy, Biological and Environmental Research (SC-33)
Biological Systems Science Division
[email protected]

Funding

This work was supported by the Great Lakes Bioenergy Research Center, DOE Office of Science, Biological and Environmental Research program under award DE-SC0018409, and by the DOE Joint BioEnergy Institute, DOE Office of Science, Biological and Environmental Research program under contract no. DE-AC02-05CH11231 between Lawrence Berkeley National Laboratory and DOE.

References

Mahon, E. L., et al. 2022. “Exogenous Chalcone Synthase Expression in Developing Poplar Xylem Incorporates Naringenin into Lignins,” Plant Physiology 188(2), 984–96. DOI:10.1093/plphys/kiab499.

Unda, F., et al. 2022. “A New Approach to Zip-Lignin: 3,4-Dihydroxybenzoate Is Compatible with Lignification,” New Phytologist 235(1), 234–46. DOI:10.1111/nph.18136.