Relative Significance of the Negative Impacts of Hemicelluloses on Enzymatic Cellulose Hydrolysis Is Dependent on Lignin Content: Evidence from Substrate Structural Features and Protein Adsorption

The biomass recalcitrance of the lignocellulose cell wall constructed by its chemical components, especially hemicelluloses and lignin, has become a bottleneck for the efficient release of glucose. The presence of hemicelluloses has been considered as a major factor limiting the enzymatic digestibility of lignocellulose biomass. However, most of the reported works on the effect of hemicelluloses removal on cellulose hydrolysability were conducted via dilute acid pretreatment at high temperature (>160 °C), and inconsistent conclusions have been found. In the present work, we studied the effects of xylan content on enzymatic digestibility of wheat straw cellulose in the cases of high and low lignin contents. Particularly, xylan removal was achieved by sulfuric acid hydrolysis under mild conditions (120 °C) to minimize lignin melting and migration in the cell wall and lignin structure modification. As revealed by various structure characterizations, when no lignin was removed, xylan removal by dilute acid hy...