چكيده لاتين
Absatract
This study was conducted with the aim of enhancing biobutanol production from lignocellulosic residues (sugarcane bagasse and corn cobs) through cellulase enzyme immobilization and its application in enzymatic hydrolysis. First, the chemical composition of the biomasses was determined based on the standard NREL method, and the percentages of cellulose, hemicellulose, and lignin were calculated. Subsequently, five different nanocarriers were synthesized, including iron oxide nanoparticles, polyaniline–iron oxide, polyaniline–multi-walled carbon nanotube–iron oxide, iron oxide coated with nanocellulose, and chitosan–iron oxide beads. Cellulase was immobilized using both physical adsorption and covalent bonding via EDC–NHS coupling, and its activity was measured using the DNS assay and spectrophotometry at 530 nm. The results indicated that immobilization on the polyaniline–multi-walled carbon nanotube–iron oxide substrate exhibited the highest efficiency. The immobilized enzyme could be reused for up to three consecutive cycles without losing more than 60% of its activity, whereas the free enzyme was only reliable for a single use. The optimal conditions for the immobilized enzyme were determined to be a temperature of 50 °C and a pH range between 4.5 and 5. Hydrolysis comparison showed that in the oligomeric liquid derived from sugarcane bagasse, free enzyme produced 3.21 g/L xylose and 9 g/L glucose, while the immobilized enzyme yielded 5.22 g/L xylose and 6.55 g/L glucose. Similarly, for corn cobs, hydrolysis with the free enzyme resulted in 8.8 g/L xylose and 11.6 g/L glucose, whereas the immobilized enzyme released 6.33 g/L xylose and 10.55 g/L glucose. The resulting sugar solutions were used as substrates for Clostridium cultivation. Gas chromatography (GC) analysis revealed that under optimal conditions, the highest ABE production reached 9.8 g/L, accompanied by 2.7 g/L acetone, 3.1 g/L butanol, and 4.5 g/L ethanol. Overall, cellulase immobilization on nanomagnetic supports not only enhanced hydrolysis efficiency and fermentable sugar yield but also enabled enzyme recovery and reuse, thereby contributing to improved biobutanol production.
