Lignocellulosic biomass, as an inexpensive, abundant, an‎d renewable raw material, is a highly promising feedstock for biofuel production. 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. Enzymatic hydrolysis of the pretreated solids under optimal conditions (180 °C an‎d 10 % organic acid) produced 34.1 g/L of fermentable sugars with a yield of 88.7 %. 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 process suggests a promising approach for the efficient valorization of xylose-rich lignocellulosic materials such as SB. Moreover, sugarcane bagasse was employed as a carrier for cell immobilization in repeated-batch fermentation, enhancing product formation by 9-15 %. To further enhance the sustainability of the process, we explored the use of bacterial autolysate, which is obtained through the natural autolysis of cells, as a substitute for costly mineral supplements. The results showed that minerals play a crucial role in shifting bacterium from acid production to solvent production, an‎d the autolysate naturally contains enough minerals to support this metabolic transition. Remarkably, adding only 0.5 ml of autolysate to a mineral deficient medium restored butanol production to levels comparable to those achieved with conventional chemical supplements. This substitution not only removes the need for expensive mineral nutrients but also recycles internal process residues, marking an important step toward creating a more circular an‎d sustainable bioprocess.

حميد زيلوئي

كيخسرو كريمي

محسن نصرتي , صفورا ميرمحمدصادقي , محمد هادي جزيني