Area-Selective Depolymerization of Hydroxycinnamates Visualized by Raman Imaging in Miscanthus sinensis cv. Cell Wall

Area of Science:

• Biomass Refinery
• Plant Cell Wall Ultrastructure
• Biopolymer Chemistry

Background:

• Lignin-carbohydrate complexes (LCCs) impede efficient lignocellulosic biomass processing.
• Understanding the dissolution of LCC components is crucial for biomass valorization.

Purpose of the Study:

• To visualize the depolymerization of hydroxycinnamates (HCMs) within LCCs during NaOH treatment.
• To investigate the spatial distribution and kinetics of HCM and lignin dissolution in Miscanthus sinensis.

Main Methods:

• Confocal Raman microspectroscopy was employed to monitor HCM dissolution.
• Successive NaOH (2.5% w/w) treatment was applied to Miscanthus sinensis biomass.
• Raman spectral and imaging analyses quantified depolymerization in different cell wall compartments.

Main Results:

• Mild NaOH treatment preferentially depolymerized HCMs in highly lignified middle lamella areas (>66.0%).
• Lignin depolymerization occurred preferentially in sclerenchyma fiber and parenchyma secondary walls over 25 min.
• HCM depolymerization strongly correlated with lignin depolymerization in middle lamella regions (R² > 0.96).

Conclusions:

• NaOH treatment effectively breaks down LCCs by targeting HCMs and lignin.
• Targeting HCM and lignin depolymerization is key for efficient herbaceous biomass refinery.
• Confocal Raman microspectroscopy provides valuable insights into LCC structural changes during biomass treatment.