Enhanced bioethanol Production from Wheat Bran Feedstock by a Mild Oxalic Acid Pretreatment

Organic acid pretreatment is one of the most promising methods to pretreat lignocellulose biomass due to its mild condition and weak corrosion to reactor. In this study, five different organic acids were used for wheat bran pretreatment, and the enzymatic hydrolysis yields of pretreated feedstocks were evaluated. Among these organic acids, oxalic acid pretreatment demonstrated the highest glucose yield of 87.93%. Subsequently, the optimization of oxalic acid pretreatment parameters was conducted including temperature, time, solid-liquid ratio, and acid usage. A high glucose yield of 96.92% was obtained at the optimal conditions: 0.8% of oxalic acid usage, 1:10 of solid-liquid ratio, and 130 ℃ for 15 min. FTIR, XRD and SEM revealed the mechanism of improved hydrolysis efficiency after oxalic acid pretreatment. Finally, the pretreated wheat bran was used for separate hydrolysis and ethanol fermentation (SHF) at 20% (w/w) solids loading. After 36 h, 23.87 g/L ethanol was produced by Saccharomyces cerevisiae DQ1 with all glucose consumed, with the yield of 0.12 g/g dry virgin wheat bran. This study provided a new insight into wheat bran pretreatment for biofuel production by a mild oxalic acid pretreatment method.