Production of High-Purity Cellobiose by Synergistic Hydrolysis of Cellulosic Substrate Using Endoglucanases from Different Sources

Using cellulase to degrade cellulose for cellobiose production is an economically competitive pathway for the high-value utilization of lignocellulose. Cellobiohydrolases hydrolyze cellulose into cellobiose but suffer severe product inhibition, whereas endoglucanases (EGs) randomly cleave cellulose chains into oligosaccharides. Three heterologously expressed EGs from different sources (PcCel45A, BsCel5, and GtCel5A) were screened for their ability to degrade cellulose into cellobiose, and their hydrolysis processes were characterized. Using PcCel45A and BsCel5 to hydrolyze Avicel step-by-step at a protein ratio of 1:1 produced cellobiose with a purity of 90.99% and a yield of 1.2 g per 100 g of Avicel. Further studies revealed that PcCel45A and BsCel5 cannot degrade cellobiose, and their activities are not inhibited by the product, showing their advantage in cellobiose production. Additionally, adsorption kinetics and thermodynamic analyses indicated that PcCel45A and BsCel5 exhibited distinct adsorption mechanisms. This study provides a promising new strategy for the high-value utilization of lignocellulose.