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Factors Impacting Ethanol Production from Grain Sorghum in the Dry-Grind Process¹

¹Contribution No. 06-362-J from Kansas State Agricultural Station, Manhattan, KS 66502. ²Department of Biological and Agricultural Engineering, Kansas State University, Manhattan, KS 66506. ³USDA-ARS Grain Marketing and Production Research Center, Manhattan, KS 66502. Names are necessary to report factually on available data; however, USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. ⁴Department of Grain Science and Industry, Kansas State University, Manhattan, KS 66506. ⁵StrathKirn Inc., Chesterfield, MO 63017. ⁶Department of Agronomy, Kansas State University, Manhattan, KS 66506. ⁷Monsanto, 7159 N. 247th West, Mt. Hope, KS 67108. ⁸Corresponding author. Phone: 785-532-2919. Fax: 785-532-5825. E-mail: dwang@ksu.edu

The goal of this research is to understand the key factors affecting ethanol production from grain sorghum. Seventy genotypes and elite hybrids with a range of chemical compositions and physical properties selected from ≈1,200 sorghum lines were evaluated for ethanol production and were used to study the relationships of composition, grain structure, and physical features that affect ethanol yield and fermentation efficiency. Variations of 22% in ethanol yield and 9% in fermentation efficiency were observed among the 70 sorghum samples. Genotypes with high and low conversion efficiencies were associated with attributes that may be manipulated to improve fermentation efficiency. Major characteristics of the elite sorghum genotypes for ethanol production by the dry-grind method include high starch content, rapid liquefaction, low viscosity during liquefaction, high fermentation speed, and high fermentation efficiency. Major factors adversely affecting the bioconversion process are tannin content, low protein digestibility, high mash viscosity, and an elevated concentration of amylose-lipid complex in the mash.