Pilot-scale high-consistency mechanical refining improves enzymatic saccharification of lignocellulosic feedstock

The natural recalcitrance of lignocellulosic biomass poses a major challenge for biorefineries aiming to convert these materials into fuels, chemicals, and polymers. This study explored the impact of pilot-scale high-consistency mechanical refining on the enzymatic depolymerization of lignocellulosic biomass when associated with low-severity hydrothermal (HPTB) and steam explosion (SEPTB) pretreatments, 180 °C for 15 min and 190 °C for 10 min respectively. Under industrially relevant conditions and using sugarcane bagasse as model lignocellulosic feedstock, we observed that the mechanical refining had a distinct effect on the fiber morphology depending on the pretreatment process. While statistical analyses indicated no correlation between refining parameters and saccharification efficiency for HPTB, an 8% increase in glucose release was observed for SEPTB with mechanical refining. Scanning electron microscopy revealed enhanced fiber morphology and delamination in SEPTB material after mechanical refining, suggesting increased porosity and accessibility for enzymes. Furthermore, distinct chemical compositions were observed between HPTB and SEPTB materials, aligning with the distinct responses to mechanical refining. These findings highlight the potential of combining mechanical refining with steam explosion pretreatment to improve the enzymatic depolymerization of lignocellulosic biomass, advancing the current knowledge on the application and challenges of high-consistency mechanical refining in lignocellulosic biorefineries.