Insight into the structure-function relationships of deep eutectic solvents during rice straw pretreatment

Area of Science:

• Biomass Pretreatment
• Green Chemistry
• Renewable Energy

Background:

• Rice straw is an abundant lignocellulosic biomass resource.
• Efficient pretreatment is essential for converting rice straw into biofuels and valuable chemicals.
• Deep eutectic solvents (DESs) offer a promising alternative to conventional pretreatment methods.

Purpose of the Study:

• To investigate the efficacy of choline chloride (ChCl) or lactic acid (Lac) based DESs for rice straw pretreatment.
• To establish structure-property relationships of DESs influencing biomass deconstruction.
• To correlate DES properties with xylan removal and subsequent cellulose digestibility.

Main Methods:

• Pretreatment of rice straw using various DES formulations.
• Characterization of DES properties, including hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) characteristics.
• Quantification of xylan removal and lignin content.
• Enzymatic hydrolysis to determine cellulose digestibility.

Main Results:

• DES pretreatment efficiency is dependent on both HBDs and HBAs.
• DESs with strong electron-withdrawing groups enhanced xylan removal.
• Xylan removal showed a negative correlation with the pKa values of HBDs.
• Enzymatic cellulose digestibility was positively and linearly related to the extent of xylan removal.

Conclusions:

• The rational design of DESs, focusing on HBD properties and electron-withdrawing groups, can optimize rice straw pretreatment.
• Xylan removal is a key factor for improving cellulose digestibility in DES-pretreated biomass.
• These findings provide a foundation for developing novel DES systems for efficient biomass conversion.