Operational patterns affecting lactic acid production in ultrafiltration cell recycle bioreactor

Area of Science:

• Biotechnology
• Biochemical Engineering
• Industrial Microbiology

Background:

• High cell density systems are crucial for efficient bioproduct manufacturing.
• Membrane bioreactors offer potential for cell retention and enhanced productivity.
• Lactic acid is a key platform chemical with diverse industrial applications.

Purpose of the Study:

• To investigate lactic acid production using an ultrafiltration tubular membrane reactor with cell recycling.
• To evaluate the impact of different operational conditions, including dilution rates and start-up modes, on fermentation performance.
• To identify optimal operating parameters for maximizing lactic acid concentration and productivity.

Main Methods:

• Utilized a tubular ultrafiltration membrane reactor for continuous cell recycling.
• Assessed three different dilution rates (0.20 h(-1), 0.40 h(-1), and 0.58 h(-1)).
• Compared two start-up modes: continuous (membrane open) and batch (membrane closed).

Main Results:

• The dilution rate of 0.40 h(-1) yielded the best overall performance in terms of lactic acid concentration and productivity.
• Continuous start-up mode resulted in higher membrane permeabilities compared to batch start-up.
• Operational stability was maintained around a membrane permeability of 15 L/m(2) h, indicating steady-state operation.

Conclusions:

• The ultrafiltration membrane cell recycle reactor enables high lactic acid concentrations and productivities simultaneously.
• The system demonstrates long operational periods at reasonable membrane permeabilities and good mechanical stability.
• Optimal operation at a dilution rate of 0.40 h(-1) with a continuous start-up mode is recommended for efficient lactic acid production.