Secrets of Cellulose

Stimulus funding from the American Recovery and Reinvestment Act of 2009 (ARRA) is meant to advance scientific research that will make a meaningful difference in the nation's future, particularly in the area of renewable energy. A perfect example is the Department of Energy's (DOE) award of $21 million over five years to Penn State to fund the new Center for Lignocellulose Structure and Formation.

One of 46 Energy Frontier Research Centers established nationwide, Penn State's center (which will also sponsor collaboration with researchers at North Carolina State and Virginia Tech) is part of a major effort to accelerate the scientific breakthroughs required to create a new 21st century energy economy.

diagram of cellulose synthesis

According to co-director Daniel J. Cosgrove, the Penn State Center will use cutting edge approaches and an interdisciplinary team—including physicists, material scientists, computational modelers and engineers—to study the molecular biology of cellulose.

Cellulose, says Cosgrove, is vital to future fuels. "The biggest solar collectors on Earth are plants which use sunlight to convert atmospheric carbon dioxide into complex structural materials like cellulose and lignin," he explains. "These make up wood, paper, cotton and many other everyday materials; globally, they represent a huge untapped reserve of biorenewable energy. Our new center will try to pry loose the secrets of how these molecules interact to form these substances that have so many practical uses as an energy source."

Cosgrove and colleagues—including co-director Jeffrey Catchmark—are working to understand the structure and formation of plant cell walls, or lignocellulose. Such information will be important for transforming cellulose into a more affordable and sustainable feedstock for ethanol production.

The main limitation in existing biomass-to-biofuel production is the high cost of dissolving the tough fibrous plant material, such as corn stover, switchgrass, and fast-growing trees. Currently, the best treatment is to soak the fibers in enzymes, adding 30 to 50 cents per gallon to the cost of the ethanol fuel produced.

"Even after decades of research, cellulose synthesis is not very well understood," Catchmark notes. "We don't know how the cells assemble this chemical barrier to weather, insects and other organisms. The cell wall is very difficult to degrade."

A decade ago, the Cosgrove lab discovered a new group of proteins, dubbed 'expansins' for their role in allowing plant cell walls to expand as the plant grows. These "wall-loosening" proteins show promise in speeding the breakdown of cellulose material into sugars. Explains Cosgrove, the expansins strip off surface polymers so the cellulose layers can be pulled apart to allow the enzymes to act on all of the layers of material at once. The hope? That expansins will help transform the industrial process for making cellulosic biofuels into a cost-competitive, cleaner, renewable energy source.

"This is the most abundant biomass on the planet," says Cosgrove. "This is the material in which most of the organic carbon on Earth is found and that the DOE wants to convert back into simple sugars and then into ethanol."

Virendra Puri, one of the Penn State researchers involved in the Center, comments, "Once we unlock the mystery of how the materials go together — how they are intertwined — and we can learn to take them apart, then the possibilities are vast."

Daniel J. Cosgrove, Ph.D., is professor of biology in the Eberly College of Science and director of the Center for Lignocellulose Structure and Formation; e-mail dcosgrove@psu.edu. Jeffrey Catchmark, Ph.D., is associate professor of agricultural and biological engineering in the College of Agricultural Sciences and co-director of the Center; jcatchmark@engr.psu.edu.

Last Updated May 18, 2010