Ozonolysis of wheat bran in subcritical water for enzymatic saccharification and polysaccharide recovery

Abstract

The destarched wheat bran was pretreated with ozonolysis, subcritical water (SW), and their combinations to improve its enzymatic digestion and hemicellulose solubilization. Ozonolysis caused lignin destructions and partial leach of hemicelluloses, leading to the formation of oxalic acids. Taking advantage of these effects, the sequential combinations of ozonolysis and SW showed synergy, resulting in a 3-fold hydrolysis outcome relative to the individual SW treatment. Eventually, the combined pretreatment achieved a high hemicellulose removal (86%) and saccharification yield (85% for glucose) under a mild SW condition (160 °C for 30 min). Apart from morphological destructions, FTIR and TGA results indicated different structural changes caused by ozonolysis and SW. Hemicellulose was shown as the major factor hindering enzymatic hydrolysis. Additionally, the soluble polysaccharides generated by these pretreatments were characterized, showing that the single SW pretreatment was better for polysaccharide recovery. These findings may help to maximize the benefits of wheat bran biorefinery.