Evaluation of the multi-seeded (msd) mutant of sorghum for ethanol production

Grain sorghum [Sorghum bicolor (L.) Moench], a cost effective crop in semiarid regions, is an underestimated supplement to corn in starch based ethanol production. Twenty-three multi-seeded (msd) mutant sorghums and one wild type sorghum BTx623 were evaluated for ethanol production and chemical composition, pasting properties, and grain structure on ethanol yield and fermentation efficiency. Starch contents of the msd mutant sorghums ranged from 66.31 to 75.65%, while the starch content of BTx623 was 74.25%. The protein, fat and free amino nitrogen (FAN) contents of the msd mutant sorghums ranged from 9.44–13.33%, 0.81–2.03% and 873.2–925.4 μg/g, respectively. The ethanol fermentation efficiency of msd mutant sorghums ranged from 87.29 to 92.54%. Taking into account that msd mutant sorghum can produce more than twice the amount of seed weight per panicle as wild type BTx623, msd mutant M2, the highest ethanol yield sample, could produce more than twice the amount of ethanol as wild type BTx623. All sorghum samples can be classified into three groups based fermentation rate: fast, medium and slow. For msd mutant sorghums with starch content higher than 71%, fermentation efficiencies were higher than 90%, and ethanol yields were higher than 470 L/ton sorghum. In addition, the fermentation curves showed most of msd mutant sorghums took less time to complete fermentation (40–50 h), indicating msd mutant sorghums have a great potential for biofuel application due to their high starch content, high fermentation efficiency, and final ethanol yield. Taking into account the best msd mutant sorghum that can produce more than twice the amount of seed weight as wild type sorghum, the best msd mutant could produce more than twice the amount of ethanol as wild type.