Simultaneous pretreatment of wheat straw with ball-milling and laccase to improve saccharification and exergy analysis of pretreatment-enzyme hydrolysis process

To solve the energy crisis and environmental pollution caused by fossil fuels, the simultaneous pretreatment of wheat straw with laccase and ball-milling was proposed for the first time to achieve efficient conversion of lignocellulose, inspired by the digestive system of termites in nature. FTIR and XRD analysis showed that simultaneous pretreatment could degrade more lignin, reduce the crystallinity of cellulose, and increase the porosity by 26.3%∼80.1% compared with the control, which promoted the subsequent enzymatic hydrolysis. Under the optimal control parameters (ball milling speed of 500 rpm, ball milling time of 12 h, and slurry concentration of 5 wt%), the conversion ratios of cellulose and hemicellulose reached 99.2% and 75.3% in 72 h, representing a 2.5-fold and 4.1-fold increase compared to the control. The exergy efficiencies of pretreatment and enzymatic hydrolysis were 52.7% and 91.3%, respectively, and the overall exergy efficiency of simultaneous pretreatment was 56.6% with standardized exergy loss of 3.0 kJ/kJ monosaccharide. Overall, a new simultaneous pretreatment strategy was proposed in this study to improve the saccharification rate of wheat straw and systematically evaluated the energy efficiency of the process with exergy indexes.