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Evaluation and Strategies to Improve Fermentation Characteristics of Modified Dry-Grind Corn Processes

¹Agricultural and Biological Engineering Department, University of Illinois at Urbana-Champaign, University of Illinois, Urbana, IL 61801. ²Corresponding author. Phone: 217-333-9510. Fax: 217-244-0323. E-mail: vsingh@uiuc.edu ³Eastern Regional Research Center, ARS, USDA, Wyndmoor, PA. Mention of brand or firm names does not constitute an endorsement by University of Illinois or USDA above others of similar nature not mentioned.

New corn fractionation technologies that produce higher value coproducts from dry-grind processing have been developed. Wet fractionation technologies involve a short soaking of corn followed by milling to recover germ and pericarp fiber in an aqueous medium before fermentation of degermed defibered slurry. In dry fractionation technologies, a dry degerm defiber (3D) process (similar to conventional corn dry-milling) is used to separate germ and pericarp fiber before fermentation of the endosperm fraction. The effect of dry and wet fractionation technologies on the fermentation rates and ethanol yields were studied and compared with the conventional dry-grind process. The wet process had the highest fermentation rate. The endosperm fraction obtained from 3D process had lowest fermentation rate and highest residual sugars at the end of fermentation. Strategies to improve the fermentation characteristics of endosperm fraction from 3D process were evaluated using two saccharification and fermentation processes. The endosperm fraction obtained from 3D process was liquefied by enzymatic hydrolysis and fermented using either separate saccharification (SS) and fermentation or simultaneous saccharification and fermentation (SSF). Corn germ soak water and B-vitamins were added during fermentation to study the effect of micronutrient addition. Ethanol and sugar profiles were measured using HPLC. The endosperm fraction fermented using SSF produced higher ethanol yields than SS. Addition of B-vitamins and germ soak water during SSF improved fermentation of 3D process and resulted in 2.6 and 2.3% (v/v) higher ethanol concentrations and fermentation rates compared with 3D process treatment with no addition of micronutrients.