Submitted to: Cereal Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/3/2006
Publication Date: 1/31/2007
Citation: Corredor, D.Y., Bean, S., Wang, D. 2007. Pretreatment and Enzymatic Hydrolysis of Sorghum Fiber. Cereal Chem. 84:61-66. Interpretive Summary: Sorghum is a drought and heat tolerant grain with starch content similar to that of maize that is increasingly being used to produce fuel ethanol in the Great Plains. While the starch can easily be broken down into sugars to be fermented, parts of the grain such as the bran are not used in this type of fermentation process. Thus this project investigated methods to treat sorghum bran so that sugars can be produced for fermentation. Using a combination of treatments including starch degradation, hot water, and enzymatic hydrolysis was found effective at producing sugars which could then be used to produce fuel ethanol. This research may lead to the utilization of new inputs, currently a by product of fuel ethanol production, as a new source for biofuel production.
Technical Abstract: Sorghum fiber has potential to serve as a low-cost feedstock for production of fuel ethanol. Sorghum fiber from a decortication process was used for this study. The approximate chemical composition of sorghum fiber is 30% starch, 18% hemicellulose, 11% cellulose, 11% protein, 10% crude fat, and 3% ash. The objective of this research was to develop and optimize pretreatment methods to improve enzymatic hydrolysis of sorghum fiber. Methods for pretreatment and enzymatic hydrolysis of sorghum fiber involved hot water treatment (10% solid, w/v) at 130 ºC for 20 min, acid hydrolysis (H2SO4), starch degradation, and enzymatic hydrolysis (60 h, 50°C, 0.9% v/v) with commercial cellulase and hemicellulose enzymes. Total sugar yield by using enzymatic hydrolysis alone was 9%, obtained from 60 h enzyme hydrolysis. Hot water treatment facilitated and increased access of the enzymes to hemicellulose and cellulose, improving total sugar yield up to 34%. Using a combination of starch degradation, optimum hot water treatment, and optimum enzymatic hydrolysis resulted in maximum total sugar yield up to 75%.