Effective enzymatic saccharification of dilute NaOH extraction of chestnut shell pretreated by acidified aqueous ethylene glycol media

• Effective combination pretreatment of chestnut shell was successfully demonstrated.
• High enzymatic saccharification of chestnut shell was achieved.
• Pretreated chestnut shell (50 g/L) was effectively saccharified.
• The recovered hydrolyzates containing glucose was fermented into ethanol efficiently.
• The combination pretreatment shows high potential application in future.

Chestnut shell (CNS) is one kind of promising feedstocks for the production of chemicals and biofuels. To effectively utilize CNS, a combined ethylene glycol–HClO4–water (88.8:1.2:10, w/w/w) pretreatment at 130 °C for 30 min with dilute NaOH (1 wt%) extraction at 90 °C for 1 h was employed to pretreat CNS. The porosity, morphology, and crystallinity of the pretreated solid residue were correlated with the enhancement of enzymatic saccharification. It was found that dilute NaOH extraction of CNS pretreated by acidified aqueous ethylene glycol media could be effectively saccharified. After 72 h, the reducing sugars and glucose from the hydrolysis of 50 g/L pretreated CNS by a cocktail of enzymes could be obtained at 77.8% and 65.4% yield, respectively. Finally, the recovered hydrolyzates containing glucose had no inhibitory effects on the ethanol fermenting microorganism. In conclusion, this combination pretreatment has high potential application in future.