Effective conversion of lignocellulose to fermentable sugars using engineered Clostridium thermocellum with...

Consolidated bio-saccharification (CBS) is a promising approach for producing fermentable non-grain sugars from lignocellulosic biomass. The natural cellulose-degrading bacterium Clostridium thermocellum has been engineered to produce β-glucosidase (BGL) CaBglA using an antibiotic-dependent plasmid system, serving as a whole-cell biocatalyst for CBS processes. In this study, we first constructed the C. thermocellum strain GB2, which features chromosomal integration of the caBglA gene. This strain achieved 94 % cellulose-to-glucose conversion in a low-cost medium system, outperforming the previously developed BGL-producing C. thermocellum strains. For hemicellulose valorization, we further engineered GB2-derived strains by either plasmid-based or chromosomal integration expression of CcXyl0074, a dual-function hydrolase xylan from Clostridium clariflavum, using corn waste as a substrate. These strains exhibited simultaneously enhanced cellulolytic and xylanolytic activities. This work provides upgraded biocatalysts for lignocellulosic biorefineries, aligning with circular economy principles through the use of low-cost media and agricultural waste biomass.