Submitted to: Journal of Cereal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/9/2008
Publication Date: 3/1/2009
Citation: Zhao, R., Bean, S., Wang, D., Park, S., Schober, T.J., Wilson, J.D. 2009. Small-scale Mashing Procedure for Predicting Ethanol Yield of Sorghum Grain. Journal of Cereal Science. 49:230-238. Interpretive Summary: A small-scale mashing (SSM) procedure requiring only 300 mg of sample was investigated as a possible method of predicting ethanol yield of sorghum grain. This procedure had the advantage of requiring only a small quantity of sorghum, use of common industrial enzymes, high repeatability, high efficiency and low cost of per-sample analysis. The 18 sorghum samples tested showed strong, linear correlations between completely hydrolyzed starch from the SSM and ethanol yields from both traditional (R squared = 0.86) and simultaneous saccharification and fermentation procedures (R squared = 0.93). CHS proved a reliable indicator for ethanol yield. Thus this methodology can be used to rapidly and inexpensively screen breeders samples and be used by the ethanol industry to screen samples for fermentation performance.
Technical Abstract: A small-scale mashing (SSM) procedure requiring only 300 mg of sample was investigated as a possible method of predicting ethanol yield of sorghum grain. The initial SSM procedure, which was conducted similarly to the mashing step in a traditional fermentation test, hydrolyzed just 38.5-47.2% of total sorghum starch to glucose. The initial procedure was simplified to contain only one liquefaction step, which did not influence subsequent saccharification. Thereafter, parameters such as temperature, pH, enzyme dosage and saccharification time were optimized. Results showed that 91.2-97.5% of the total starch in 18 sorghum grains had been hydrolyzed to glucose using the following conditions: liquefaction at 86 degrees Celsius for 90 min, 20 microliters of alpha-amylase per 30 g of sample; pH adjustment by adding 50 microliters of 2M acetate buffer at pH 4.2 to each microtube; saccharification at 68 degrees Celsius for 90 min, 200 microliters of amylogucosidase per 30 g of sample. There were strong linear correlations between completely hydrolyzed starch (CHS) from SSM and ethanol yields from both traditional (R squared = 0.86) and simultaneous saccharification and fermentation (SSF, R squared = 0.93) procedures. CHS was a better indicator for predicting ethanol yield in fermentation than total starch.