Percival Zhang Turns Cellulose into Starch

Virginia Tech professor Y H Percival Zhang has developed a process that can transform waste plant cellulose into starches to be used as food or turned into biodegradable or even edible packaging materials.

“Cellulose and starch have the same chemical formula,” Zhang explains. “The difference is in their chemical linkages. Our idea is to use an enzyme cascade to break up the bonds in cellulose, enabling their reconfiguration as starch.”

Zhang’s breakthrough has the potential to change the world’s food equation. Cellulose is by far the earth’s most abundant carbohydrate. It makes up the cellular walls giving structure to plants, including the stalks and leaves of crop plants like corn as well as plants currently not considered food crops.

Zhang’s cascading enzyme process would allow harvesting of plants that grow naturally without need for the water, pesticides, fertilizers and intensive labor that typically goes into raising food crops. It can also multiply the yield of current food crops like corn by turning the cellulose in the stem, leaves and husk into a combination of 30% amylose — a form of edible but slow-digesting starch — and the remainder into starches that can be hydrolyzed into glucose for use in food or to be turned into ethanol.

Amylose is a form of resistant starch which breaks down slowly in the digestive tract. Foods with high amylose content like long-grain rice lowers the glycemic load and is more healthful, especially for diabetics. It is broken down by the digestive enzyme α-amylase into maltotriose and maltose which are ready energy sources. Its resistance to breakdown allows amylose to act as dietary fiber as well as a prebiotic, food for beneficial gut bacteria.

The starches produced by Zhang’s process is also ideal for making edible clear films for biodegradable food packaging. Zhang suggests it can even serve as a high-density hydrogen storage carrier for hydrogen storage and distribution.

What makes Zhang’s breakthrough significant is that its “simultaneous enzymatic biotransformation and microbial fermentation” is easy to scale up for commercial production. It requires no costly equipment, heat or chemicals, and produces no waste. The key enzymes immobilized through the use of magnetic nanoparticles can be recycled through magnetic manipulation.

Zhang was assisted in the research by Virginia Tech visiting scholar Hongge Chen and Chun You, a postdoctoral researcher from China.

Zhang has been an associate professor of biological systems engineering in Virginia Tech’s College of Agriculture and Life Sciences and the College of Engineering since June of 2010. He was an assistant professor at VT since August 2005. He began his research career in May 2004 at Dartmouth College where he obtained his PhD in chemical engineering and biotechnology in 2002. Zhang earned his masters in biochemical engineering from East China University of Science and Technology in 1996 and a bachelors in 1993.

Zhang’s research was published Monday in the Early Edition of the Proceedings of the National Academy of Sciences.