Second Generation Bioethanol Production from Soybean Hulls Pretreated with Imidazole as a New Solvent

Soybean hulls (SH) are the main industrial waste from soybean processing, representing 5–8% of the whole grain. Imidazole was employed for the hydrothermal pretreatment of SH and further bioethanol production. Different pretreatment temperatures (120 and 180 °C) and times (1 and 3 h) were tested. Lignin removal and glucose yield were significantly influenced by temperature. After 48 h of enzymatic hydrolysis of imidazole-treated SH (120 °C, 1 h), 32.7 g/L of glucose and 9.4 g/L of xylose were obtained. A maximum bioethanol yield of 78.9% was reached after 12 h of fermentation by Saccharomyces cerevisiae using SH enzymatic hydrolysate. Imidazole appears to be a potential alternative to pretreat lignocellulosic wastes such as SH for the production of second-generation biofuels and other biomolecules.