BIOREACTOR ADDITION AND WEIGHT CONTROL – MODES TO IMPROVE ACCURACY AND REPRODUCIBILITY IN THE BIOREACTOR

There are different fermentation modes in bioreactor systems: batch, fed-batch, and continuous. The batch mode is the simplest. The bioreactor is filled with a medium containing all the necessary components for the growth of the organism or the production of specific biomolecules, such as metabolites or proteins. However, this mode has a production limitation: when the limiting substrate is consumed, cell growth stops, resulting in limited productivity and low cell density.

Alternative operational strategies include fed-batch and continuous modes, designed to increase cell density and productivity in open systems. In fed-batch mode, a concentrated solution of the limiting substrate is added to the bioreactor to prevent issues such as catabolite repression, which occurs when the initial substrate concentration is too high. Continuous fermentation, on the other hand, is a process where the medium is constantly removed and replaced with fresh medium at the same flow rate.

VOLUMETRIC ADDITION STRATEGY (PERISTALTIC PUMPS)

The volumetric dosing system is the most common method for adding acid, base, antifoam, other substrates, and fresh medium to bioreactors. Peristaltic pumps are frequently used due to several advantages:

• No risk of fluid contamination, as only the tubing comes into contact with the liquid.
• Low maintenance requirements.
• High capacity for handling viscous and shear-sensitive fluids.
• Prevention of backflow.
• Delivery of a fixed volume of fluid per rotation.

However, these pumps are not self-priming, which may cause slight variations in the actual flow compared to existing performance curves. Additionally, flow output may fluctuate due to tube wear, requiring periodic tension adjustments, especially in prolonged operations. Variations may also occur due to the rheological properties of the substrate solution, making it essential to regularly measure and verify pump performance in critical applications requiring precision.

GRAVIMETRIC ADDITION STRATEGIES

For applications where the volume added to the bioreactor is critical, BIONET recommends gravimetric control strategies such as BWC (Bioreactor Weight Control) and AWC (Addition Weight Control). These strategies use precision balances combined with variable-speed pumps and advanced software, ensuring greater accuracy.

• AWC (Addition Weight Control): Enables precise automatic addition based on the weight variation of the substrate container measured by an external balance. The weight data is sent to the ROSITA or MARTA software, which regulates the pump flow and records the weight data.
• BWC (Bioreactor Weight Control): Requires a balance connected to the bioreactor to measure levels or maintain a constant weight in continuous processes. The bioreactor’s weight is monitored in real-time and integrated into the software for more precise control of liquid addition and removal pumps.

Both modes eliminate variability associated with volumetric systems, such as peristaltic pump tube wear or substrate solution density fluctuations, ensuring higher accuracy and reproducibility.

REQUIRED TECHNOLOGY MODULES: AWC AND BWC WITH BSCALE

These functionalities are provided by the bScale module, which is compatible with all Bionet bioreactors. The bScale allows multiple balances to be connected and integrates weight data into the ROSITA or MARTA software, providing additional control and real-time weight data visualization. This module supports different brands and precision ranges of balances, ensuring user flexibility.