Size Effects on Acid Bisulfite Pretreatment Efficiency: Multiple Product Yields in Spent Liquor and Enzymatic Digestibility of Pretreated Solids

Currently, feedstock size effects on chemical pretreatment performance were not clear due to the complexity of the pretreatment process and multiple evaluation standards such as the sugar recovery in spent liquor or enzymatic digestibility. In this study, we evaluated the size effects by various ways: the sugar recovery and coproduct yields in spent liquor, the chemical and thermal properties, and enzymatic digestibility of the pretreated solids. Four initial particle sizes were employed and characterized with the geometric mean diameters, which were 10.40, 2.25, 1.49, and 0.84 mm. The results showed that a decrease in the particle size improved the hydrolysis of hemicellulose and cellulose in acid bisulfite pretreatment. Higher concentrations of hydroxymethylfurfural and furfural were produced in the pretreatment of the 0.84 and 10.40 mm particles. The maximum total sugar yield of 72% was achieved with a 2.25 mm particle size at 145 °C.