Enhancing biobutanol production by optimizing acetone-butanol-ethanol fermentation from sorghum grains through strategic immobilization of amylolytic enzymes

Abstract

Tannin-containing sorghum grains, suitable for acetone-butanol-ethanol (ABE) production by Clostridium acetobutylicum, have required pretreatment to eliminate tannins inhibiting the strain's amylolytic activity. This study investigates biobutanol production enhancement by immobilizing enzymes on polydopamine-functionalized polyethersulfone (PES) membranes with magnetic nanoparticles for Separated Hydrolysis and Fermentation (SHF) and Simultaneous Saccharification and Fermentation (SSF) processes. After multi-stage hot water treatment, TG3 sorghum (from the third stage) was used, where the enzyme-immobilized PES membrane produced 4.75 g/L of ABE (3.24 g/L butanol) under SSF, 0.85 g/L under SHF, and 1.1 g/L under simple fermentation. For TG6 (from the sixth stage), 3.23, 1.29, and 1.25 g/L of ABE was produced under SSF, SHF, and simple fermentation, respectively. This enhanced performance is due to the reduced enzyme inhibition. Reusability experiments showed that the membrane retained 30 % of initial activity after three cycles. These findings suggest that enzyme-immobilized membranes can intensify ABE production and enable integrated cell recovery. © 2025 Elsevier Ltd