Sustainable and efficient valorization of sugarcane bagasse: Integrated conversion of holocellulose into acetone, butanol, and ethanol

Abstract

The hemicellulose fraction of biomass as a fermentable carbon source is typically discarded in the most common biofuel production processes, directly impacting the overall conversion efficiency of hemicellulose-containing lignocelluloses, such as sugarcane bagasse (SB). In this study, an integrated process was developed to efficiently convert both the hemicellulose and cellulose content of SB into acetone, butanol, and ethanol (ABE), employing Clostridium acetobutylicum. The process comprised dilute acid hydrolysis, organosolv pretreatment, enzymatic hydrolysis, and fermentation. To ensure a sustainable process, the primary fermentation byproducts (i.e., acetic acid and butyric acid) were utilized as the acidic agents in the dilute acid hydrolysis of hemicellulose for xylose recovery. The amount of xylose obtained at 180 °C was 22.3 %, significantly higher than that at 150 °C, which was 7.6 %. Furthermore, purified lignin was obtained as a byproduct through ethanolic delignification, where trace acids remaining on the substrate from the dilute acid hydrolysis step enhance the delignification process. Fermentation of mixed detoxified dilute acid hydrolysate and enzymatic hydrolysate resulted in a significant increase in ABE production, elevating it from 9.9 to 12.23 g/L in the best case. This integrated and sustainable process suggests a promising approach for the efficient valorization of xylose-rich lignocellulosic materials such as SB.