Comparison Between Simple Batch and Fed-Batch Bioreactor Cultivation of Recombinant BCG

Area of Science:

• Microbiology and Biotechnology
• Vaccine Development
• Fermentation Technology

Background:

• Tuberculosis (TB) remains a major global health threat, with the existing Bacillus Calmette-Guérin (BCG) vaccine needing production modernization.
• The recombinant BCG-pertussis (rBCG-pertussis) strain offers potential dual protection against TB and whooping cough, and enhanced bladder cancer efficacy.
• Submerged cultivation techniques are explored to improve rBCG-pertussis productivity and standardization.

Purpose of the Study:

• To investigate a fed-batch cultivation strategy for producing rBCG-pertussis using L-glutamic acid.
• To evaluate the impact of pH-stat control on rBCG-pertussis growth and viability.
• To assess the effectiveness of fed-batch cultivation on cell recovery after freeze-drying.

Main Methods:

• A fed-batch cultivation strategy with pH-stat control was employed, feeding L-glutamic acid into a 1 L bioreactor.
• Three different pH levels were tested for fed-batch cultivation, with a simple batch culture used for comparison.
• Viable cell concentrations were measured before and after freeze-drying of samples harvested during cultivation.

Main Results:

• L-glutamic acid was confirmed as the optimal substrate for rBCG-pertussis growth.
• Fed-batch cultivation at pH 7.4 improved the specific growth rate after day 4, reducing cultivation time, though maximum growth rate was not enhanced.
• Fed-batch cultures demonstrated superior viable cell recovery post-freeze-drying compared to simple batch cultures, particularly for samples harvested later in the culture.

Conclusions:

• The fed-batch strategy, particularly at pH 7.4, offers advantages in reducing cultivation time for rBCG-pertussis.
• The addition of L-glutamic acid in fed-batch cultures appears to enhance cell cryoprotection during lyophilization.
• This optimized submerged cultivation method shows promise for more robust and standardized production of rBCG-pertussis.