Sodium sulfite–formaldehyde pretreatment of mixed hardwoods and its effect on enzymatic hydrolysis

In this work, mixed hardwoods were pretreated by sodium sulfite–formaldehyde (SF). The effects of SF pretreatment on the chemical compositions and enzymatic hydrolysis of mixed hardwoods were investigated. SF pretreatment temperature had a significant effect on pulp yield and delignification, resulting in an increased efficiency of enzymatic hydrolysis. After 96 h of enzymatic hydrolysis at the cellulase loading of 40 FPU/g substrate, the yields of glucan and xylan on the basis of original wood were 37% and 11% for the pulp produced with 12% sulfite charge at 170 °C for 2 h. The total sugar recovery based on the sugar in original wood was 74%. These results indicate that sulfite–formaldehyde cooking is of great potential to be a pretreatment method for a greenfield mill to produce fuel ethanol from hardwood.