Role of Steam Explosion on Enzymatic Digestibility, Xylan Extraction, and Lignin Release of Lignocellulosic Biomass

This work studies the contribution of each step of the steam explosion (residence time and sudden decompression) of wheat straw. Raw wheat straw and wheat straw with different degrees of xylan extraction were subjected to a steam explosion without residence time at 160, 180, 200, or 220 °C, in order to identify the individual contribution of the sudden pressure change upon enzymatic digestibility, xylan extraction, and lignin release. In addition, the contribution of the residence time of the biomass in the reactor before the explosion was estimated using pretreated biomass prepared by autohydrolysis at 180–220 °C with a residence time of up to 56 min. Results show that steam explosion alone does not have significant effects on digestibility, xylan extraction, or lignin release of raw wheat straw. For autohydrolyzed biomass, steam explosion of 200 °C and above increases glucose release after 72 h of enzymatic hydrolysis at an enzymatic dose of 22 mg protein/g substrate. Digestibility at several enzymatic doses were also tested. No significant differences between autohydrolyzed biomass either before or after steam explosion were observed with an enzymatic dosage of 44 mg protein/g substrate. A simple mathematical model based on experimental results is proposed to describe the effect of steam explosion variables (residence time and temperature) on digestibility.