Efficient high-solids mechanoenzymatic hydrolysis of rice straw: A synergistic strategy of hydrothermal pretreatment and additives for monosaccharides production

The valorization of lignocellulosic biomass is crucial for sustainable bioenergy production. This study systematically investigates an integrated strategy, combining hydrothermal pretreatment, additive addition, and mechanoenzymatic hydrolysis, to enhance monosaccharides production from rice straw at high solids loading while reducing enzyme usage for cost-effective saccharification. Hydrothermal pretreatment (180°C, 120 min) resulted in hemicellulose depletion and the formation of porous structures in rice straw, thereby enhancing cellulose accessibility. This process enabled the near-complete conversion of cellulose to glucose, achieving both a 98.11% yield and a glucose concentration of 134.75 g/L. Both hydrothermal pretreatment and mechanoenzymatic hydrolysis improved the efficiency of enzyme utilization under high-solids conditions. Lignin inhibition analysis suggested that hydrothermal pretreatment reduced the overall inhibitory effect of lignin and effectively alleviated its physical blocking. In static and mechanoenzymatic hydrolysis systems, the overall inhibition decreased from 14.12% to 13.01% and from 28.02% to 21.99%, respectively. Moreover, under conditions of low enzyme loading (10 FPU/g) and high solids (25% w/v), bovine serum albumin-aided mechanoenzymatic hydrolysis achieved both a 76.68% glucose yield and a concentration of 105.67 g/L within 12 h. These findings provide crucial insights for overcoming the recalcitrance of biomass and addressing the solid effects in high-solids enzymatic hydrolysis, thereby highlighting the synergistic potential of combined strategies in lignocellulosic biorefining.