Enhancement in the enzymatic digestibility of hybrid poplar with poor residual hemicelluloses after Na2SO3 pretreatment

• The sulfonic group and delignification contributed mutually for the glucose yield.
• Delignification was favorable to the introduction of sulfonic group.
• The introduced sulfonic group enhanced the enzymatic digestibility.
• The sulfonic group contributed more for the glucose yield at lower residual lignin.
• The sulfonic group could contribute 17.3% of total glucose yield (92.7%).

The aim of this work was to illustrate the contributions of delignification and the introduced sulfonic groups on the enzymatic digestibility of the Na2SO3-pretreated hybrid poplar with poor residual hemicelluloses (HPPRH). The higher the content of the introduced sulfonic group in the pretreated HPPRH was, the higher its enzymatic digestibility could be achieved. Delignification was favorable to increasing the content of sulfonic group in the pretreated HPPRH. The introduced sulfonic group contributed much more to the total glucose yield at low level of residual lignin. The introduced sulfonic groups could contribute 17.30% of total glucose yield (92.70%) and delignification could do 38.43% of it. Meanwhile, the delignification rate and the sulfonic group content in the pretreated HPRH were 59.88% and 283.51 mmol kg−1 lignin, respectively. Therefore, the sulfonic group introduced on the pretreated lignocellulosics could improve the enzymatic digestibility and make the sulfite process effective.