Tapping Plants’ Biofuel Potential

Changing the way a plant forms 
cellulose may lead to more efficient, less expensive biofuel production, according to Penn State engineers.

“What every biofuel manufacturer wants to do is to get to the sugars,” said Jeffrey Catchmark, associate professor of agricultural and biological engineering. “But the structure of cellulose itself can be an obstacle.”

Catchmark said that most of a plant’s sugar-based energy is locked up in the crystalline structure of cellulose. To make cellulose, plants create long chains of sugar that are then crystallized and densely packed into tight, ordered bundles resistant to water and other solvents. This bundling may help build strong plant cell walls, but biofuel makers must use extra effort to break down and separate the bundles and the crystalline cellulose to extract the sugars used to ferment fuels.

Using bacteria that produce cellulose as a model to test the process, the researchers discovered an approach for modifying cellulose synthesis in living plants for improved biofuel-making efficiency. During the synthesis process the researchers added glucomannan, a complex carbohydrate found in plants that sticks to cellulose, and found that it altered the structure and assembly of the cellulose, allowing it to be broken down more efficiently.

Another method to ensure the glucomannan is added during cellulose formation requires genetically engineering the plant to express or overexpress the enzymes that form the glucomannan, according to the researchers who applied for a provisional patent on the process.

By growing plants with cellulose that is less crystalized and that has fewer structured bundles, biofuel manufacturers will not need to spend as much time and effort breaking down these pretreated plants, according to the researchers. Currently, biofuel manufacturers must use several industrial processes that are time and energy intensive and relatively expensive, including chemical, mechanical, and fermentation, to break down the cellulose and separate other materials.

Matthew Swayne