Low-temperature EDA/urea pretreatment improves enzymatic hydrolysis of corn stover through changing physical and chemical structure

Pretreatment of lignocellulose at low temperature is beneficial for energy saving. Herein, a simple ethylenediamine (EDA)/urea pretreatment method at low temperature was constructed to improve enzymatic hydrolysis of corn stover. Reducing sugar content and yield up to 102.4 g/L and 93.3% were obtained when the pretreatment was conducted at 60 degrees C. Compared with NaOH and EDA alone pretreatment, EDA/urea pretreatment increased the concentration of reducing sugar by 12.0 g/L and 8.6 g/L, and the sugar yield was increased by 5.2% and 4.7%, respectively. Scanning electron microscopy (SEM) analysis showed that EDA/urea pretreatment promoted the formation of scaly structures and holes on the surface, resulting in more disorderly biomass surface and severely damaged structure. The crystallinity of corn stover pretreated with EDA/urea decreased slightly, while the crystallinity of cellulose itself decreased from 0.62 to 0.40 compared to raw biomass. Besides, specific surface area of EDA/urea pretreated corn stover was 12.0 m(2)/g, which was 13.2% higher than that of NaOH pretreated biomass. The Fourier transform infrared spectroscopy (FTIR) analysis indicated that EDA/urea pretreatment resulted in the cleavage of chemical bonds between lignin and carbohydrate. After EDA/urea pretreatment, simultaneous saccharification and co-fermentation were conducted and the ethanol yield reached 88.03%. Overall, this work demonstrated that EDA/urea pretreatment efficiently deconstructed the dense structure of lignocellulose at low temperature. It showed an attractive potential for application in the bioenergy production.