Pretreatment of wheat straw using SO2 dissolved in hot water

Efficient pretreatment is important for complete enzymatic conversion of lignocellulosic materials. Pretreatment of wheat straw with sulfur dioxide (SO2) dissolved in hot water achieved xylose and total product yields of up to 61.1% and 93.9%, respectively, based on the mass of lignocellulose in wheat straw. The apparent activation energies for hemicellulose conversion and xylose dehydration were 7.8 and 9.0 kJ/mol. FT-IR spectra of the residual solid after treatment showed that the hemicellulosic components were converted, the hydrogen bonds in cellulose were broken, but the lignin structure was not changed. Importantly, the SO2 was recovered from the product mixture by steam stripping and could be reused. Thus, the SO2–H2O system is an efficient and environmentally friendly way for the conversion of hemicellulose in wheat straw into monosaccharides, such as xylose, glucose and arabinose.