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Improvement of dry-fractionation ethanol fermentation by partial germ supplementation

Divya Ramchandran, Ping Wang, Bruce Dien, Wei Liu, Michael A. Cotta, Vijay Singh
Cereal chemistry 2015 v.92 no.2 pp. 218-223
corn, dry milling, endosperm, ethanol, ethanol fermentation, hydrolysis, starch
Ethanol fermentation of dry-fractionated grits (corn endosperm pieces) containing different levels of germ was studied with the dry-grind process. Partial removal of the 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 with 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 a high ethanol concentration (19.06% v/v) compared with control grits (18.18% v/v). Fermentation of dry-fractionated grits (92, 95, and 97% grits) obtained from a commercial facility was also compared with ground whole corn (control). Fermentation rates were slower and final ethanol concentrations were lower for commercial grits than the control sample. However, in a final experiment, commercial grits were subjected to raw starch hydrolyzing (RSH) enzyme, resulting in higher ethanol concentrations (20.22, 19.90, and 19.49% v/v for 92, 95, and 97% grits, respectively) compared with the whole corn control (18.64% v/v). Therefore, high ethanol concentrations can be achieved with dry-fractionated grits provided the inclusion of a certain amount of germ and the use of RSH enzyme for controlled starch hydrolysis.