Integrated processes for production of cellulosic and hemicellulosic biobutanol from sweet sorghum bagasse using autohydrolysis

Abstract

Different process alternatives were assessed for production of hemicellulosic and cellulosic butanol from sweet sorghum bagasse (SSB) based on integration of autohydrolysis, enzymatic hydrolysis, and ABE fermentation. The liquor obtained through single or two-stage autohydrolysis was subjected to post-hydrolysis using a commercial hemicellulases blend and fermentation by Clostridium acetobutylicum. The pretreated solids obtained at each stage of autohydrolysis were also used for ABE production through separated hydrolysis and fermentation (SHF) or simultaneous saccharification and fermentation (SSF) using a commercial cellulase blend. The two-stage autohydrolysis (at 150 °C for 30 min; 120 °C for 60 min) followed by enzymatic post-hydrolysis resulted in 6.6 g/L sugar and fermented to 4.6 g/L ABE. On the other hand, enzymatic hydrolysis and ABE fermentation of the pretreated SSB led to 4.7–5.4 g/L ABE. In this process, 32 g hemicellulosic and 85 g cellulosic ABE were produced from each kg SSB. Besides, other thirteen process alternatives were compared based on the overall yield of ABE production from SSB. In the most compact process, the four enzymatic hydrolysis and fermentation stages were combined into a single stage named “simultaneous co-saccharification and fermentation (SCSF)" leading to 21−22 g ABE/kg SSB.