Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2016
Publication Date: 2/1/2017
Publication URL: https://handle.nal.usda.gov/10113/5598765
Citation: Johnston, D., Moreau, R.A. 2017. A comparison between corn and grain sorghum fermentation rates, distillers dried grains with solubles composition, and lipid profiles. Bioresource Technology. 226:118-124.
Interpretive Summary: Existing fuel ethanol production facilities utilize corn as essentially the only feedstock. Interest in utilizing other feedstock is increasing and the potential to utilize other grains is being investigated. Grain sorghum has similar composition to corn and could potentially be utilized in existing facilities with little or no modification. While grain sorghum is similar to corn, it is not identical and these differences can potentially impact the processing steps or negatively affect the economics of the facility. To determine if the differences will impact the processing or economics of ethanol production we compared fermentation rates, yields and the distillers dried grains with solubles (DDGS) compositions for grain sorghum and corn. The results show that rates and yield of ethanol production are very similar between corn and sorghum based on starch content. DDGS yield and protein content were found to be higher for grain sorghum, potentially improving the value of this coproduct. Lipid analysis showed differences between grain sorghum and corn that could potentially decrease the value of the oil. This information will be useful for fuel ethanol production facilities, grain suppliers and animal feed processors that utilize DDGS.
Technical Abstract: Interest in utilization of feedstocks other than corn for fuel ethanol production has been increasing due to political as well as environmental reasons. Grain sorghum is an identified alternative that has a number of potential benefits relative to corn in both composition and agronomic traits. Compositionally grain sorghum is similar to corn but it is higher in protein and slightly lower in starch and oil. In order to study how these differences may impact the use of grain sorghum in existing ethanol facilities, we compared the fermentation properties of corn and grain sorghum utilizing two fermentation systems (conventional thermal starch liquefaction and native starch hydrolysis). Distillers grains with solubles (DDGS) were prepared from the fermentations and analyzed for important nutritional qualities that influence their economic value. Fermentation results indicated that protease addition influenced the fermentation rate and yield for grain sorghum, improving yields by 1-2% over non-protease treated fermentations. The DDGS produced from sorghum had a statistically significantly higher protein content relative to corn and the DDGS yields were higher as well. Lipid analysis of the DDGS showed statistically significant differences between corn and sorghum in triacylglycerol, diacylglycerol and free fatty acid levels.