Effects of hydrothermal treatment on enhancing enzymatic hydrolysis of rapeseed straw

Rapeseed straw is an annually renewable low-cost crop by-product, and it was submitted to hydrothermal treatment at temperatures ranging from 145 to 205 °C for various retention times (15–120 min). The enzymatic hydrolysis was conducted at a substrate concentration of 2% and an enzyme addition of 115 mg/g substrate. Results showed that increased pretreatment severity gradually degraded and removed hemicelluloses, and temperatures above 190 °C destroyed the crystalline structure of cellulose and led to partial delignification. The microstructure of the lignin was partially destroyed and particle-sized debris appeared on the surface of the cellulose fibres under the harsh treatment conditions. The glucose yield increased with an increase in severity and a higher saccharification ratio (95%) was achieved at a relatively low temperature (190 °C) and short retention time (15–30 min). These results suggest that hydrothermal treatment of rapeseed straw effectively dissolves hemicelluloses and remarkably enhances enzymatic hydrolysis efficiency.