LAUSR

BACKGROUND This study aimed to demonstrate the superiority of bioethanol yield and its quality from sorghum using the granular starch degrading enzyme StargenTM 002 over simultaneous saccharification and fermentation, and separate hydrolysis and fermentation using Zymomonas mobilis CCM 3881 and Ethanol Red yeast. RESULTS The bacteria were found to produce ethanol at higher yield than the yeast in all fermentations. The highest ethanol yield was obtained with Z. mobilis during 48 h of simultaneous saccharification and fermentation (83.85% theoretical yield) and fermentation with StargenTM 002 (81.27% theoretical yield). Pre-liquefaction in fermentation with StargenTM 002 did not improve ethanol yields for both Z. mobilis and S. cerevisiae. Chromatographic analysis showed twice less total volatile compounds in distillates obtained after bacterial (3.29-5.54 g L-1 ) than after yeast (7.84-9.75 g L-1 ) fermentations. Distillates obtained after bacterial fermentation were characterized by high level of aldehydes up to 65% of total volatiles) and distillates obtained after yeast fermentation of higher alcohols (up to 95% of total volatiles). The process of fermentation using granular starch hydrolyzing enzyme cocktail StargenTM 002 resulted in low amounts of all volatile compounds in distillates obtained after bacterial fermentation, but the highest amounts in distillates obtained after yeast fermentation. CONCLUSION The study emphasizes the great potential of bioethanol production from sorghum with Z. mobilis using granular starch hydrolyzing enzyme StargenTM 002, which leads to reduce water and energy consumption, especially when energy sources are strongly related to global climate change. This article is protected by copyright. All rights reserved.