Structural changes of corn stover lignin during acid pretreatment

Area of Science:

• Biomass Conversion and Biorefining
• Renewable Energy Technologies
• Biochemical Engineering

Background:

• Corn stover is a promising lignocellulosic feedstock for biofuel production.
• Efficient pretreatment is crucial for enhancing enzymatic hydrolysis of biomass.
• Understanding pretreatment effects on lignin and xylan is vital for optimizing biofuel conversion.

Purpose of the Study:

• To investigate the impact of dilute acid pretreatment severity on corn stover.
• To correlate structural changes in pretreated corn stover with enzymatic hydrolysis yields.
• To elucidate the roles of xylan solubilization and lignin degradation in biomass digestibility.

Main Methods:

• Dilute acid pretreatment of raw corn stover at varying severities.
• Enzymatic hydrolysis of pretreated biomass.
• Characterization of lignin residues using Phosphorus-31 Nuclear Magnetic Resonance (³¹P NMR) spectroscopy.
• Quantification of functional moieties and correlation with hydrolysis yields.

Main Results:

• Enzymatic hydrolysis yields exceeded 70% at moderate enzyme loadings.
• Both xylan solubilization and lignin degradation positively influenced enzyme accessibility.
• At higher temperatures, lignin degradation (increased phenolic groups) correlated better with cellulose accessibility.
• Syringyl/guaiacyl ratio in lignin increased with temperature, indicating preferential release of syringyl units.

Conclusions:

• Optimizing dilute acid pretreatment conditions is essential for efficient corn stover conversion to ethanol.
• Xylan removal and lignin modification are critical for improving cellulose digestibility.
• Understanding lignin depolymerization pathways, including syringyl/guaiacyl ratios and phenolic condensation, aids in process optimization.