Submitted to: Industrial Crops and Products
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/9/2005
Publication Date: 5/25/2006
Citation: Zhan, X., Wang, D., Bean, S., Mo, X., Sun, X.S., Boyle, D. 2006. Evaluation of ethanol production from extrusion-cooked sorghum flour. Industrial Crops and Products. 23:304-310. Interpretive Summary: Sorghum is a starch rich, drought-resistant, low input grain that is often grown in areas where it is too dry to other cereal crops. As such, sorghum represents an important renewable resource for bio-industrial products. However, grain sorghum is currently underused for such applications. The objective of this research was to investigate the use of extrusion to increase the fermentation yields of ethanol from sorghum. Extrusion uses high temperatures, pressure, and shear to disrupt the molecules in sorghum and alter their chemical properties. This process may free up starch for fermentation that is not available in the native grain. Two different types of extrusion were tested, a conventional process as well as a supercritical fluid extrusion process. Both types of extrusion increased the yield of ethanol from sorghum. Such techniques may be useful in increasing fuel ethanol production from sorghum.
Technical Abstract: Sorghum is a starch-rich grain similar to maize but has been under utilized for biobased-products and bioenergy. This study was designed to investigate the effects of conventional and supercritical fluid extrusion on ethanol production from sorghum flour. Morphology, chemical composition, and thermal properties of extruded flour were characterized. Analysis of extruded sorghum flour showed increased measurable starch content, free sugar content, and high levels of gelatinized starch. The conventional extruded, supercritical fluid extruded-, and non-extruded sorghum flour were further liquefied, saccharified, and fermented to ethanol using Saccharomyces cervisiae. The ethanol yield increased as sorghum flour concentration increased form 20% to 40% for extruded and non-extruded sorghum flours. Both conventional and supercritical fluid extruded sorghum flour showed increased ethanol yield and fermentation efficiency, with supercritical fluid extruded flour giving the highest values.