Enzymatic Saccharification of Delignified Biomass Intensified by Hydrodynamic Cavitation

Lignocellulosic biomass is a promising renewable resource for sustainable biorefineries, although its commercial use remains limited by the complex biomass structure and process inefficiencies. This work investigates the use of hydrodynamic cavitation (HC) as a process-intensification strategy during the washing step following hydrogen peroxide–acetic acid (HPAC) delignification, with the aim of enhancing subsequent enzymatic saccharification to produce glucose. Wood residues from Eucalyptus sp., Tipuana tipu, and Pinus sp. were delignified using HPAC under mild conditions (1:1 v/v glacial acetic acid: 30% w/w H2O2 solutions, at 90 °C, 15 g/L, 1 h orbital shake) and washed either by conventional soaking or by HC-assisted recirculation prior to enzymatic hydrolysis using the Novozymes Cellic CTec3 blend at optimal initial conditions (40 FPU/g substrate, pH = 5, and 53 °C). HC applied during washing significantly increased glucose yields and initial hydrolysis rates for delignified angiosperm species. Glucose yields after 28 h increased significantly for Eucalyptus sp. and Tipuana tipu compared to conventional washing, while little effect was found for Pinus sp. Overall, the glucose yield, expressed per 100 g of precursor dry mass, attained 34.5 g/100 g for Eucalyptus sp., 30.2 g/100 g for Tipuana tipu, and only 12.9 g/100 g for Pinus sp. Structural and morphological analyses indicate that the effectiveness of HC is species-dependent and might be associated with fiber disruption and the removal of inhibitory compounds rather than changes in cellulose crystallinity. Implementing HC during the washing step involved 7% extra energy compared to the energy required for HPAC, thus resulting in less energy required per unit mass of glucose generated. These results demonstrate that HC-assisted washing is an effective and energy-efficient intensification step when combined with HPAC, contributing to improved biomass valorization while avoiding harsher pretreatment conditions. Since HC is relatively simple to scale up, the proposed strategy offers an energy-convenient approach for enhancing enzymatic saccharification in sustainable biorefinery processes.