Effect of steam explosion on physicochemical properties and fermentation characteristics of sorghum (Sorghum bicolor (L.) Moench)

Steam explosion (SE) was applied to modify the physicochemical properties and fermentation characteristics of sorghum (Sorghum bicolor (L.) Moench). Scanning electron microscopy (SEM) showed that the dense structures of sorghum especially the starch granules were destroyed, and much more folds, crimps and holes appeared in sorghum starch. Cellulose, hemicellulose and proteins in sorghum tended to decrease when the SE pressure increased which were investigated by fourier transformed infrared (FTIR) spectroscopy and SDS-PAGE. SE pretreatment increased the content of reducing sugar in sorghum, and the content of reducing sugar in sorghum pretreated by SE of 2.0 MPa increased over 19 times than the control. Moreover, fermentation results indicated that the ethanol yield was over 2 times higher than the control under the pressure of 1.5 MPa. The fermentation broth increased and the fermentation residue decreased obviously by SE pretreatment than the control. The kinds and the relative contents of esters increased, especially the ethyl acetate. This study suggested that SE pretreatment could reduce the waste content and promote the ethanol production in the liquor industry.