Impact of delignification on the morphology and the reactivity of steam exploded wheat straw

• Steam exploded wheat straw was delignified to 6 different grades.
• Delignification affected the mesoporosity of the substrate.
• Delignification had no impact on the hydrolysis rate of the substrate.
• Isolated lignins were added to delignified straw and crystalline cellulose.
• The effect of lignin addition depended both on cellulose and lignin properties.

The purpose of this article was to better understand the role of lignin in the recalcitrance of lignocellulosic biomass during enzymatic hydrolysis. Steam exploded wheat straw was partially delignified with sodium chlorite to six different grades of delignification. Delignification did not have a significant impact on the enzymatic hydrolysis of the studied wheat straw in the experimental conditions tested. Inhibitive impact of lignin in terms of non-productive adsorption was then explored using soda lignin from wheat straw and kraft lignin from softwood. The addition of both lignins had a strong negative influence on the hydrolysis of highly crystalline cellulose (Avicel), whereas it impacted only slightly the hydrolysis of delignified wheat straw. These results are probably linked to the greater accessibility and surface area of steam exploded wheat straw cellulose, which are much higher than those of the crystalline cellulose Avicel.