In recent years, the concerns of depletion of non-renewable resources and the recognition of biological butanol as one of the main options to replace the current fossil fuels directed toward improving the fermentation process of acetone, butanol, and ethanol. However, the prerequisite of being a proper alternative fuel, it should be produced economically. With this regard, using of inexpensive non-food resources as a carbon source for acetone-butanol-ethanol ABE fermentation has been suggested for biobutanol production in the last few years. Sorghum is a promising substrate for biofuel production, which has previously evaluated for biobutanol production. The seed of sorghum is a source of starch that may be utilized for ABE production. In addition, its stalk contains both soluble (glucose, fructose and sucrose) and insoluble (cellulose and hemicellulose) carbohydrates that can be converted to acetone, butanol and ethanol. In this study, sweet sorghum was evaluated as an energy crop for acetone, butanol and ethanol production by Clostridium acetobutylicum . Different parts of sweet sorghum, i.e., seeds, juice, and stalk (a lignocellulosic material) have been utilized for ABE production. Using a single -stage extraction, sorghum juice with 35.1 (g/l) sugars was obtained, which was converted to ABE with maximum efficiency of 24.4 % of ABE. Before enzymatic hydrolysis, an organosolv treatment with organic solution containing 50% v/v acetone, and 0.1% w/w sulfuric acid used for the pretreatment of lignocellulosic residues (bagasse). Pretreatment of bagasse at 180 o C and 60 min resulted in obtaining the maximum total sugar concentration (35.3 g/l) through the enzymatic hydrolysis; however, hydrolysated bagasse pretreated at 150 o C for 90 min resulted in the highest ABE concentration (5.9 g/l). In addition, sweet sorghum seed containing more than 70% starch directly fermented to ABE with maximum yield of 37.1%. Based on the results, by separate fermentation of seed, juice and hydrolysated of bagasse, each kg of sweet sorghum produced 144.6 g of the solvents. This amount is 2.4 times greater than the amount of solvents produced by direct fermentation of entire parts of sorghum.
