Monday, April 30, 2007

Consolidated conversion of hulled barley into ethanol using chemo, thermo, and enzymatic treatment

Tae Hyun Kim1, Frank Taylor2, and Kevin, B. Hicks2. (1) Agricultural and Biosystems Engineering, Iowa State University, 3101 NSRIC, Ames, IA 50011, (2) Eastern Regional Research Center, USDA-ARS, 600 East Mermaid Lane, Wyndmoor, PA 19038

Barley can be a corn substitute for ethanol production in corn deficit region. Major obstacles in barley ethanol conversion process are (1) difficulty of clean separation of hull (lignocellulose) from the endosperm, which makes the downstream conversion process more complicated (2) high viscosity of mash in liquefaction step due to mixed linkage b-glucan polysaccharides, and (3) difficulty of the conversion of the lignocellulosic hull into ethanol. The intention of this study is to convert both lignocellulose and starch in the hulled barley into ethanol simultaneously without any hull separation and grinding steps. The process uses dilute sulfuric acid solutions, because the hydronium ion in the liquid can attack and hydrolyze b-glucans in the cell walls of endosperm and the aleurone layer and also the hemicellulose in the hull. Hydrolysis of the hemicellulose and some removal of lignin bring about a pretreatment effect for the lignocellulosic portion of the barley. An advantage of pretreatment may be it has a potential to lower the enzyme dosage, which is a significant cost factor, because of its hydrolysis effect on cellulose, hemicellulose, and starch. In this study, whole hulled barely, was treated using 0.1~1.0 wt. % of sulfuric acid at various temperature from 110ºC to 170ºC.

The whole hulled barley treated by this process was further evaluated by subjecting them to enzymatic hydrolysis and simultaneous saccharification and fermentation (SSF). This paper provides experimental details and overall assessment on the consolidated conversion process.