Continuous Steam Explosion of Wheat Straw by High Pressure Mechanical Refining System to Produce Sugars for Bioconversion

This study demonstrated the use of a pressurized mechanical refining system for the continuous steam explosion pretreatment of wheat straw. Wheat straw was first impregnated with either dilute acid (0.5% sulfuric acid) or water and then steam exploded in an Andritz pressurized refiner. The effect of a range of pretreatment conditions, including refining retention time and steam pressure/temperature on the resulting substrate composition and hydrolysability as well as overall sugars yield was investigated. For autohydrolysis, the optimum conditions, 198 C/6 min gave an enzymatic hydrolysis yield of 93.3% and an overall glucose yield of 85.8%, while 198 C/4 min gave an enzymatic hydrolysis yield of 88.7% and overall glucose yield of 88.4%. Longer retention time increased the enzymatic hydrolysability but reduced the overall glucose yield owing to the degradation reaction during pretreatment. For acid pretreatment, the most favourable condition for enzymatic hydrolysis and overall glucose yield coincided at 178 C /6 min.