Wheat straw is an abundant byproduct from wheat production in EU and USA. Its chemical composition and low-cost make it an attractive feedstock for a bioethanol biorefinery.

In this work, wheat straw was subjected to autohydrolysis treatments in order to selectively hydrolyse the hemicellulose fraction. The effects of temperature (150-240ºC) and non-isothermal reaction time on the composition of both liquid and solid phase were evaluated and interpreted using the severity factor (log Ro). The operational conditions leading to the maximal recovery of soluble hemicellulose (xylo-oligosaccharides and xylose) were established for log Ro = 3.96 and correspond to 60% of the feedstock xylan. Under these conditions, a solubilization of 83% arabinan and 98% acetyl groups also occurred. Glucan was only slightly solubilized (10%), which enable an enrichment of the solid phase to contain 57% glucan. Delignification was not extensive, being utmost 15% for the tested conditions.

The yields of soluble products, e.g., glucose, arabinose, acetic acid and degradation compounds, such as, furfural, hydroxymethylfurfural and formic acid are also presented and the overall liquid fraction composition is discussed regarding liquor fitness for fermentation purposes. 

This work has been funded by CEBio (AdI) and BIOREFINO (FCT) projects.