Cellulase kinetics as a function of cellulose pretreatment
Andreas S Bommarius1, Adrian Katona, Sean E Cheben
1School of Chemical and Biomolecular Engineering, Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332-0363, USA. andreas.bommarius@chbe.gatech.edu
Metabolic Engineering
|July 24, 2008
Summary
Pretreating microcrystalline cellulose (Avicel) and adding beta-glucosidase significantly accelerates cellulose hydrolysis. Enzyme jamming at high concentrations explains the slowing rate during this biofuel conversion process.
Area of Science:
- Biotechnology
- Biochemical Engineering
- Renewable Energy
Background:
- Cellulose hydrolysis is a key step in biofuel production.
- Cellobiose accumulation inhibits cellulase activity, slowing hydrolysis.
- Pretreatment methods aim to enhance cellulose accessibility for enzymes.
Purpose of the Study:
- To investigate the effect of different pretreatments on microcrystalline cellulose (Avicel) for enzymatic hydrolysis.
- To evaluate the impact of beta-glucosidase addition on accelerating cellulose conversion.
- To understand the phenomenon of enzyme jamming and its role in hydrolysis rate.
Main Methods:
- Microcrystalline cellulose (Avicel) underwent acid, alkaline, and organosolv pretreatments.
- Enzymatic hydrolysis was performed using cellulase (Celluclast) with and without beta-glucosidase.
- Enzyme adsorption and conversion rates were monitored under varying enzyme concentrations.
Main Results:
- Beta-glucosidase addition significantly accelerated cellulose hydrolysis, especially at a 20:1 activity ratio.
- All pretreatments slightly increased cellulose crystallinity but did not affect conversion-time behavior.
- Enzyme jamming at high enzyme concentrations (beyond 400 U/L cellulase/8 kU/L beta-glucosidase) was observed and explained the rate slowdown.
Conclusions:
- Optimizing beta-glucosidase addition is crucial for efficient cellulose hydrolysis.
- Enzyme jamming is a significant factor limiting hydrolysis rates at high enzyme loadings.
- Pretreatment method and fractal kinetics did not influence the jamming parameter.
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