Coupled enzymatic hydrolysis and ethanol fermentation: ionic liquid pretreatment for enhanced yields

Area of Science:

• Biomass Conversion
• Renewable Energy
• Biotechnology

Background:

• Pretreatment of lignocellulose is crucial for biofuel production.
• Acid-catalyzed thermochemical treatments are common but have limitations.
• Ionic liquids (ILs) offer novel solvent properties for lignocellulose pretreatment.

Purpose of the Study:

• To evaluate the effectiveness of four ionic liquids (ILs) and two switchable ILs (SILs) for lignocellulose pretreatment.
• To compare IL-based pretreatment with traditional acid treatments.
• To assess sugar release and ethanol fermentation yields from various lignocellulosic materials.

Main Methods:

• Pretreatment of Spruce, Pine, Birch, Reed Canary Grass (RCG), and Pine bark using DBU-MEA-SO2, DBU-MEA-CO2, [Amim][HCO2], and [AMMorp][OAc].
• Comparison with acid pretreatment and untreated controls.
• Enzymatic hydrolysis to determine glucan and hemicellulose conversion.
• Ethanol fermentation of resulting hydrolysates.

Main Results:

• IL-treated substrates achieved excellent glucan-to-glucose conversion (75-97%), significantly outperforming acid treatments (13-77%).
• Up to 92% hemicellulose release was observed after enzymatic hydrolysis of IL-treated lignocelluloses.
• Ethanol production directly correlated with sugar concentrations in the hydrolysates.

Conclusions:

• SIL DBU-MEA-SO2 demonstrated superior pretreatment efficiency, particularly for softwood substrates (Spruce, Pine).
• DBU-MEA-CO2 and [AMMorp][OAc] showed comparable or better hydrolysis efficiency for Birch and RCG.
• Pine bark's amorphous nature limited the benefits of the applied pretreatments for yield improvement.