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Published on: March 9, 2021
Microwave-assisted lignin isolation using the enzymatic mild acidolysis (EMAL) protocol
Luca Zoia1, Marco Orlandi, Dimitris S Argyropoulos
1Dipartimento di Scienze dell'Ambiente e del Territorio, Università degli Studi di Milano-Bicocca, Piazza della Scienza 1, 20126 Milano, Italy.
Journal of Agricultural and Food Chemistry
|October 17, 2008
Summary
Microwave-assisted enzymatic mild acidolysis lignin (EMAL) isolation offers higher yields and purity. This optimized method preserves lignin structure, improving efficiency for wood biomass processing.
Area of Science:
- Biomass Valorization
- Green Chemistry
- Wood Chemistry
Background:
- Lignin-carbohydrate linkages are prevalent in wood, posing challenges for efficient lignin isolation.
- Traditional lignin isolation methods, like enzymatic mild acidolysis lignin (EMAL), can be harsh, affecting lignin yield and structure.
- Improving selectivity and reducing the intensity of the acidolysis step is crucial for enhanced lignin recovery.
Purpose of the Study:
- To explore microwave irradiation as a replacement for traditional reflux in the EMAL protocol.
- To enhance the selectivity of lignin-carbohydrate bond cleavage and minimize lignin structural changes.
- To investigate the impact of various microwave conditions on lignin yield, purity, and structural integrity.
Main Methods:
- The EMAL protocol was modified using a microwave reactor instead of conventional reflux for the mild acidolysis step.
- Lignin was isolated from spruce (softwood) under varied microwave power, heating time, hydrochloric acid concentration, and water content.
- Lignin purity and yield were assessed gravimetrically, while structural characteristics were analyzed using quantitative (31)P NMR and SEC.
Main Results:
- Microwave-assisted EMAL yielded lignins with high purity (approximately 90%), comparable to conventional methods.
- Gravimetric yields of lignin were significantly greater under microwave conditions.
- Quantitative (31)P NMR and SEC analyses indicated that the lignin structure remained largely consistent with traditional EMAL, showing similar levels of beta-aryl ether bonds, phenolic hydroxyls, and carboxylic acids.
Conclusions:
- Microwave irradiation is an effective tool for improving the EMAL lignin isolation protocol.
- The optimized microwave-assisted EMAL process enhances lignin yield and purity without compromising structural integrity.
- This approach offers a more efficient and potentially greener method for obtaining high-quality lignin from wood biomass.
