High-concentrated substrate enzymatic hydrolysis of pretreated rice straw with glycerol and aluminum chloride at low cellulase loadings

Abstract

Rice straw was pretreated with glycerol and AlCl3 for enzymatic hydrolysis at low cellulase loadings. Based on a central composite design, 83% delignification, 94% hemicellulose removal, and 92% cellulose recovery (or 76% cellulose in solid residue) were achieved under the optimized pretreatment conditions (0.08 mol/L AlCl3 as catalyst at 146.8 °C for 20 min with 90% glycerol). During glycerol-AlCl3 pretreatment, the lignin-carbohydrate complex was depolymerized, resulting in the complex and recalcitrant construction of straw effectively being destroyed. The enzyme adsorption ability of pretreated straw was 16.5 times that for the original sample. After pretreatment, glucose yield was increased by 2.4 times to 74% for 48 h. Moreover, concentrated solid (15%) with low cellulase loading (3.3 FPU/g dry substrate) achieved 58.6% glucose yield, and further increased by 12% to 65.7% by adding Tween 80. Glycerol-AlCl3 pretreatment was a promising approach to realize high-concentrated solid hydrolysis for sugars at low cellulase loadings.