Influence of pretreatment severity on structural changes, lignin content and enzymatic hydrolysis of sugarcane bagasse samples

Abstract

The structural changes, lignin content and enzymatic hydrolysis of dilute acid pretreated bagasse from 19 varieties of sugarcane were investigated. Chemical compositions varied significantly between the materials. Glucose yield after enzymatic hydrolysis also differed significantly among the samples. The differences in glucose yields were not eliminated by increasing the pretreatment severity. Glucose yield showed a positive correlation with total dye and orange dye adsorption, whereas with blue dye adsorption it showed a weak correlation. The crystallinity index increased with the increasing pretreatment severity as a result of the removal of the amorphous components of the biomass. The degree of polymerization decreased with the increase in pretreatment severity. However, the change in either crystallinity index or degree of polymerization did not correlate with glucose yield. The results suggest that the lignin modification/reallocation is a key factor for improving cellulose accessibility of sugarcane bagasse.

Sugarcane biomass conversion influenced by lignin

“…However, such strategies as the commonly used dilute acid pretreatment do not only cause the breakdown of the biomass but also contribute to lignin reorganization. This may vary according to the severity of the pretreatment and the nature of the lignocellulosic material . The breakdown of the cellulose‐hemicellulose‐lignin complex during acid pretreatment increases the surface area of the fiber and decreases the degree of polymerization and crystallinity of the cellulose .…”

“…Different biomass characteristics require specific pretreatment conditions to overcome the intrinsic recalcitrance . In fact, low lignin contents in the biomass represent decreased recalcitrance and physicochemical properties for the conversion process …”

“…Greater accumulation of lignin in the stem implies a lower quality biomass raw material for the production of biofuels on the one hand . On the other hand, a low concentration of lignin in the sugarcane and any modifications in its recalcitrance, as well as low ash content are fundamental parameters for the efficiency of the conversion of lignocellulosic material into ethanol …”

“…This may vary according to the severity of the pretreatment and the nature of the lignocellulosic material. 6,7 The breakdown of the cellulose-hemicellulose-lignin complex during acid pretreatment increases the surface area of the fiber and decreases the degree of polymerization and crystallinity of the cellulose. 1 This type of pretreatment can break cellulose chains but hemicellulose is more susceptible due to its amorphous character, its high polydispersity, and its lower degree of polymerization.…”

“…1 This type of pretreatment can break cellulose chains but hemicellulose is more susceptible due to its amorphous character, its high polydispersity, and its lower degree of polymerization. 5,7 Other pretreatment strategies, including organosolv pretreatment, which involves the use of organic solvents and acids as catalysts, have shown good selectivity for sugarcane bagasse, resulting in high physicochemical modification, with improved accessibility to cellulose by cellulase enzymes. 8 During organosolv pretreatment a reaction occurs between an alcohol (methanol, isobutanol, cyclohexanol, or benzyl alcohol) and a mineral acid, thereby forming the soluble alcoholic lignin with 30% yield.…”