ARS | Publication request: Influence of Stenocarpella maydis infected corn on the dry grind ethanol process

Submitted to: International Starch Technology Conference
Publication Type: Abstract Only
Publication Acceptance Date: June 8, 2011
Publication Date: June 8, 2011
Citation: Dien, B.S., Wicklow, D.T., Singh, V., Moreau, R.A., Moser, J.K., Cotta, M.A. 2011. Influence of Stenocarpella maydis infected corn on the dry grind ethanol process [abstract]. International Starch Technology Conference. p. 82.

Technical Abstract: Widespread epidemics of Stenocarpella ear rot (formerly Diplodia ear rot) have occurred throughout the central U.S. Corn Belt in recent years with reports of some fields containing more than 50% mummified ears. Ears infected within two weeks of silking may be completely mummified with white to grayish brown mycelium covering light-weight, shriveled, and lusterless light brown kernels. The severity of ear rotting decreases sharply with later infection dates during kernel development. Ears infected later in the growing season may appear normal with disease symptoms seen as discolored kernel embryos after the ear is broken in the middle. There have been no reports of S. maydis toxicity to livestock in North America. The influence of S. maydis infected grain on corn ethanol production is unknown. In this study, approximately 200 S. maydis infected ears of variety ‘Heritage 4646’ were hand-harvested in 2010 from a production field in central Illinois and segregated into one of five levels of ear rot severity based upon visual symptoms. The concentration of ergosterol, a sterol produced by fungi but not plants, was observed to increase with the severity of ear rot (127-306.5 ug/g) and none was detected in the control corn. These corn samples were initially characterized for bulk properties and chemical composition. Corn test weights declined with progression of the disease and were 42.6% lower for the most severely rotted grain sample. Accompanying changes in composition were also apparent. Oil content decreased (4.7 to 1.5%) and fiber increased (6.6 to 9.6%) but starch content remained largely invariant. Oil composition also varied among the infected samples. Corn samples were converted to ethanol using a laboratory scale process that mimics the typical corn dry grind ethanol process using a simultaneous saccharification and fermentation (SSF). Ethanol yields were similar on an equivalent weight basis (2.77-2.85 gal/bu) and starch to ethanol conversion efficiencies were 91.5–98.3%. However, Distiller's Dried Grains with Solubles (DDGS) composition was modified and significantly reduced in oil content (10.9 to 3.8%). Based upon these results, we conclude that Stenocarpella ear rot will affect DDGS composition but not ethanol yield on an equivalent weight basis.