Model-based fed-batch for high-solids enzymatic cellulose hydrolysis.

Area of Science:

• Biotechnology
• Biochemical Engineering
• Renewable Energy

Background:

• Enzymatic hydrolysis of cellulose is crucial for biofuel production.
• High-solids operation reduces costs but poses mixing challenges in stirred tank reactors (STRs).
• Existing kinetic models are often not applied for process design and optimization.

Purpose of the Study:

• To develop an optimization strategy for cellulose saccharification at high insoluble solids levels (>15%).
• To adapt a cellulose hydrolysis model for fed-batch operation.
• To improve final sugar concentration in bioreactors.

Main Methods:

• Modified a previously developed batch enzymatic hydrolysis model to include fed-batch operation.
• Developed a feeding profile by solving model differential equations to maintain constant insoluble solids concentration.
• Conducted experiments in bench-scale STRs using pretreated corn stover and cellulase enzymes.

Main Results:

• A feeding strategy was successfully developed to manage insoluble solids concentration during fed-batch hydrolysis.
• Fed-batch operation in STRs achieved cellulose conversion profiles comparable to batch shake-flask reactors.
• Final cellulose conversions reached approximately 80% of theoretical at a cumulative solids level of 25% (w/w).

Conclusions:

• Fed-batch operation is a viable strategy to overcome mixing limitations in high-solids enzymatic hydrolysis.
• This approach allows for increased final sugar concentrations without requiring excessively high initial solids.
• The developed strategy offers a pathway for more efficient and cost-effective cellulose saccharification processes.