Evaluation of steam pretreatment on sweet sorghum bagasse for enzymatic hydrolysis and bioethanol production

Sweet sorghum bagasse (SSB) was steam-pretreated at various temperatures, residence times and SO2 impregnation dosages. A 23 factorial experimental design was employed to investigate the effects of temperature, residence time and SO2 impregnation and their interactions on enzymatic hydrolysis and ethanol production. The results showed that temperature, residence time, SO2 impregnation and the interaction of residence time and SO2 impregnation significantly affected enzymatic hydrolysis in an order of residence time > temperature > SO2 impregnation > the interaction of residence time and SO2 impregnation. Both of water-soluble and water-insoluble fraction derived from steam pretreatment were used for ethanol production, respectively. The results indicated that the effects of mentioned factors and their interactions on total ethanol yield were not significant. However, 200 °C, 7.5 min and 2.5% SO2 impregnation could be determined as a group of optimal pretreatment conditions, in which the highest ethanol yield of 15.3 g/100 g SSB (dry basis) could be obtained without pentose fermentation.