Regenerating cellulose from ionic liquids for an accelerated enzymatic hydrolysis

Area of Science:

• Biomass Conversion and Bioenergy
• Green Chemistry and Sustainable Solvents
• Biocatalysis and Enzyme Technology

Background:

• Efficient conversion of lignocellulosic biomass to fuel ethanol is crucial for renewable energy.
• Pretreatment of lignocelluloses is key to accelerating cellulose enzymatic hydrolysis.
• Previous studies show ionic liquids (ILs) can dissolve cellulose, and regenerated cellulose exhibits faster saccharification.

Purpose of the Study:

• To investigate a wider range of ILs, including novel ones, for cellulose pretreatment and regeneration.
• To identify inexpensive, efficient, and environmentally benign IL solvents for cellulosic biomass processing.
• To evaluate the impact of IL-based pretreatment on cellulose crystallinity, accessibility, and enzymatic hydrolysis rates.

Main Methods:

• Regeneration of cellulose from various chloride- and acetate-based ionic liquids (ILs).
• Characterization of regenerated cellulose for crystallinity and accessibility to cellulase.
• Enzymatic hydrolysis assays using Trichoderma reesei cellulase on regenerated and untreated cellulose substrates.

Main Results:

• All regenerated celluloses exhibited significantly reduced crystallinity (58-75% lower) and increased accessibility (>2 times) compared to untreated substrates.
• Regenerated Avicel((R)) cellulose, filter paper, and cotton showed 2-10 times faster hydrolysis rates.
• Complete hydrolysis of Avicel((R)) was achieved in 6 hours with a cellulase/substrate ratio of 3:20 at 50°C; cellulase showed enhanced thermal stability up to 60°C in regenerated cellulose presence.

Conclusions:

• Ionic liquid-based pretreatment is a promising route for enhancing cellulose enzymatic hydrolysis, leading to more efficient biofuel production.
• Regenerated cellulose demonstrates superior susceptibility to enzymatic breakdown, enabling faster and more complete conversion.
• Thorough removal of IL residues post-regeneration is recommended due to potential cellulase inactivation during hydrolysis.