Alkaline incubation improves the saccharification of poplar after sodium chlorite pretreatment with ultra-low cellulase loading

Abstract

The limitation of xylan hydrolysis is a characteristic problem of sodium chlorite (SC) pretreatment, which greatly restricted the saccharification of SC-pretreated lignocelluloses. In this work, the effect of alkali incubation on the xylan hydrolysis of SC-pretreated poplar was investigated. SC pretreatment of poplar removed 84.7% lignin, which yielded 71.2% glucose and 60.0% xylose under a cellulase loading of 20 filter paper units (FPU)/g dry matter (DM). The subsequent alkali incubation reduced the acetyl group, surface lignin, and surface chlorine contents of SC-pretreated poplar. Glucose and xylose yields were increased to 92.4% and 86.3%, respectively, by incubating SC-pretreated samples with 1.0% NaOH at 50 °C for 1 h using a cellulase loading of 2 FPU/g DM. Both Tween 80 and xylanase improved the enzymatic hydrolysis yield of SC-pretreated poplar. Alkali incubation showed a 9-fold decrease in cellulase loading and increased the xylose yield of SC-pretreated poplar by 119.8%. This work overcame the limitation of xylan hydrolysis in sodium chlorite-pretreated lignocelluloses and represented a novel method to efficiently saccharification of poplar with ultra-low cellulase loading.