|Ramchandran, Divya - UNIVERSITY OF ILLINOIS|
|Wang, Ping - U.S. DEPARTMENT OF ENERGY|
|Liu, Wei - UNIVERSITY OF ILLINOIS|
|Singh, Vijay - UNIVERSITY OF ILLINOIS|
Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2014
Publication Date: 4/1/2015
Publication URL: http://handle.nal.usda.gov/10113/62179
Citation: Ramchandran, D., Wang, P., Dien, B.S., Liu, W., Cotta, M.A., Singh, V. 2015. Improvement of dry fractionation ethanol fermentation by partial germ supplementation. Cereal Chemistry. 92:218-223.
Interpretive Summary: The United States produces over 12 billion gallons of fuel ethanol per year from corn. Isolation of the corn germ prior to fermentation allows for recovery of valuable corn oil as a co-product and removes non-fermentable fiber from the fermentation tanks. The latter can increase plant productivity. However, removal of the germ fraction has been observed to lead to sluggish and incomplete fermentations presumably because the germ contains micro-nutrients that enhance ethanol fermentation. This paper demonstrates that partial back mixing of just 2% of the isolated germ into the degermed corn meal counteracts this effect. Furthermore, the use of newly developed raw starch hydrolysis technology, which is practiced in several plants commercially, leads to higher ethanol titers compared to when whole corn is fermented. As such, this paper demonstrated a method that allows for recovery of corn germ and that enhances ethanol titer. This paper will be of interest to current corn ethanol producers and associated engineering firms.
Technical Abstract: Ethanol fermentation of dry fractionated grits (corn endosperm pieces) containing different levels of germ was studied using the dry grind process. Partial removal of germ fraction allows for marketing the germ fraction and potentially more efficient fermentation. Grits obtained from a dry milling plant were mixed with different amounts of germ (2, 5, 7 and 10% germ of the total sample) and compared to control grits (0% germ). Fermentation rates of germ supplemented grits (2, 5, 7 and 10% germ) were faster than control grits (0% germ). Addition of 2% germ was sufficient to achieve high ethanol concentration (19.06% v/v) compared to control grits (18.18% v/v). Fermentation of dry fractionated grits (92, 95 and 97% grits) obtained from a commercial facility was also compared to ground whole corn (control). Fermentation rates were slower and final ethanol concentrations were lower for commercial grits than control sample. However, in a final experiment, commercial grits were subjected to raw starch hydrolyzing enzymes (RSH) resulting in higher ethanol concentrations (20.22, 19.90, 19.49% v/v for 92, 95 and 97% grits, respectively) compared to whole corn control (18.64% v/v). Therefore, high ethanol concentrations can be achieved with dry fractionated grits provided inclusion of certain amount of germ and the use of RSH for controlled starch hydrolysis.