Improvement of acetone, butanol and ethanol production from rice straw by acid and alkaline pretreatments

Rice straw was hydrolyzed and fermented to acetone, butanol, and ethanol by Clostridium acetobutylicum bacterium. Concentrated phosphoric acid and alkaline treatment with NaOH were used for pretreatment of the straw prior to enzymatic hydrolysis using commercial cellulase and β-glucosidase. The enzymatic hydrolysates were then anaerobically fermented by C. acetobutylicum. Hydrolysis of the alkaline pretreated straw resulted in production of 163.5 g glucose from each kg of untreated rice straw which was then fermented to 45.2 g butanol, 17.7 g acetone, and 1.2 g ethanol. Additionally, concentrated phosphoric acid pretreatment and subsequent hydrolysis resulted in production of 192.3 g glucose from each kg straw from which 44.2 g butanol, 18.2 g acetone, and 0.6 g ethanol were produced after 72 h fermentation. Increasing the produced ABE from less than 10 g to higher than 62 g from each kg straw by the treatments suggested the alkaline and phosphoric acid pretreatments as promising processes for efficient production of ABE from rice straw.