Wheat Straw Autohydrolysis: Process Optimization and Products Characterization

Wheat straw was subjected to autohydrolysis treatments in order to selectively hydrolyze the hemicellulose fraction. The effects of temperature (150-240°C) and non-isothermal reaction time on the composition of both liquid and solid phases were evaluated and interpreted using the severity factor (log R ₀). The operational conditions leading to the maximum recovery of hemicellulose-derived sugars were established for log R ₀ = 3.96 and correspond to 64% of the original (arabino)xylan with 80% of sugars as xylooligosaccharides. Under these conditions, a solubilization of 58% xylan, 83% arabinan, and 98% acetyl groups occurred. Glucan was mainly retained in the solid phase (maximum solubilization 16%), which enables an enrichment of the solid phase to contain up to 61% glucan. Delignification was not extensive, being utmost 15%. The yields of soluble products, including sugars, acetic acid, and degradation compounds, such as, furfural, 5-hydroxymethylfurfural furfural obtained suggest the fitness of liquid stream for fermentation purposes or to obtain xylooligosaccharides with potential applications in food, pharmaceutical, and cosmetic industries.