Yan Zhang
Research Director (National Corn to Ethanol Research Center)
Session: Speaker – Fiber Panel
Topic: Fermentation of Starch, Resistant Starch, Cellulose, and Xlyan
Summary:
The carbohydrates in corn kernel, starch, cellulose and xylose, are the main sugar sources which can be consumed by Saccharomyces cerevisiae to make ethanol. While starch is dominant (around 70%) in corn kernel and the conversion technology is mature, the cellulosic fraction of cellulose (2 – 4%) and xylan (4 – 6%) can contribute dramatically to ethanol production, after full conversion to glucose and xylose followed by consumption using a right yeast strain. The extra ethanol produced can lead to over 11% yield increase compared with starch-based ethanol, and the extra volume is considered as cellulosic ethanol under the Renewable Fuel Standard (RFS) program.
At lab scale, we have run numerous fermentation trials to compare the ethanol yield between corns starch fermentation and corn starch fermentation with addition of cellulase at the beginning of fermentation, so called industrial in situ 1.5G fermentation, and we have observed statistically sound higher ethanol yield from the latter, and higher carbon dioxide production from the latter as well. In addition, we are able to show more than 50% of the ethanol yield increase was due to cellulose conversion, based on the quantitation of residual cellulose and starch content in DDGS utilizing highly accurate and precise analytical methods to for starch and cellulose in corn matrix.
We have also explored several pathways to convert xylan in corn matrix into xylose, and explore the potential of C5C6 yeast to make more cellulosic ethanol.
Bio:
Dr. Yan Zhang, the Director of Research/Associate Research Faculty at the National Corn-to-Ethanol Research Center (NCERC) of Southern Illinois University Edwardsville, received her Ph.D in analytical chemistry from the University of Arkansas in Fayetteville. After graduation, she worked at the University of Illinois Urbana-Champaign as an environmental chemist, and she also spent five years working at a pharmaceutical company developing analytical methods, and helping with production trouble shooting and FDA submissions. Her career focus has been at NCERC to work on projects related to make biofuel or bioproducts from corn or other feedstock like biomass or municipal solid waste. She is helping NCERC to support a rich research portfolio covering but not limited to, corn to ethanol, corn kernel fiber conversion, and biomass pretreatment and conversion.