Researchers turn corn stover into amylose starch

By Susanne Retka Schill | April 18, 2013

A team of Virginia Tech researchers have adapted existing technologies to make a new product, transforming cellulose into amylose. One target market for the amylose would be functional foods, said lead researcher Y.H. Percival Zhang, an associate professor of biological systems engineering in the College of Agriculture and Life Sciences and the College of Engineering.

Starch is one of the most important components of the human diet and provides 20 to 40 percent of our daily caloric intake. The type of starch that Zhang’s team produced is amylose, a linear resistant starch that is not broken down in the digestion process and acts as a good source of dietary fiber. It has been proven to decrease the risk of obesity and diabetes.

 “Besides serving as a food source, the starch can be used in the manufacture of edible, clear films for biodegradable food packaging,” Zhang said.  “It can even serve as a high-density hydrogen storage carrier that could solve problems related to hydrogen storage and distribution.”

Zhang used a novel process involving cascading enzymes to transform cellulose into amylose starch. The process adapts the familiar simultaneous saccharification and fermentation (SSF) process used by ethanol plants. The new approach takes cellulose from nonfood plant material, such as corn stover, converts about 30 percent to amylose, and hydrolyzes the remainder to glucose suitable for ethanol production.

This bioprocess called “simultaneous enzymatic biotransformation and microbial fermentation” is easy to scale up for commercial production. It is environmentally friendly because it does not require expensive equipment, heat, or chemical reagents, and does not generate any waste. The key enzymes immobilized on the magnetic nanoparticles can easily be recycled using a magnetic force. The amylose itself is relatively easily separated with centrifuges, Zhang added. For an ethanol producer, the amylose would be a higher valued product than ethanol.

The research was published in the early edition of the Proceedings of the National Academy of Sciences of the United States of America. “After the paper came out we got a lot of inquiries,” Zhang adds. “Now we’re looking for a good industrial partner.”

Zhang designed the experiments and conceived the cellulose-to-starch concept. Zhang and Virginia Tech visiting scholar Hongge Chen are the inventors of the cellulose-to-starch biotransformation, which is covered under a provisional patent application. Chun You, a postdoctoral researcher from China at Virginia Tech, and Chen conducted most of the research work.

Support for the current research comes from the Department of Biological Systems Engineering at Virginia Tech. Additional resources were contributed by the Virginia Tech College of Agriculture and Life Sciences’ Biodesign and Bioprocessing Research Center, the Shell GameChanger Program, and the U.S. Department of Energy BioEnergy Science Center, along with the Division of Chemical Sciences, Geosciences and Biosciences, Office of Basic Energy Sciences of the Department of Energy. Chen was partially supported by the China Scholarship Council.