Fed-Batch Culture

Fed-batch culture is a widely used bioprocessing strategy combining aspects of batch culture with controlled substrate feeding to optimize cell growth and product formation. In this semi-closed system, nutrients are strategically added during fermentation, while the accumulated products and biomass remain within the bioreactor until the end of the operation. This controlled addition of substrates allows for better management of growth kinetics, nutrient limitation, and metabolite accumulation.

Two primary configurations of fed-batch culture are distinguished by how the substrate is introduced. In variable-volume fed-batch culture, substrates are added in concentrations equivalent to those in the initial culture medium. This results in a progressive increase in the culture volume over time. This method is beneficial for maintaining consistent nutrient concentrations and reducing the buildup of inhibitory byproducts.

On the other hand, fixed-volume fed-batch culture involves the addition of highly concentrated substrates. Due to the limited volume increment, this approach maintains a nearly constant working volume while supporting extended growth phases. It is often favored in processes requiring tight control over culture parameters or downstream processing constraints that limit volume expansion.

Cyclic fed-batch culture introduces an additional layer of complexity by incorporating periodic partial harvests of the culture medium. Fresh substrate is replenished after each harvest to sustain microbial activity and prolong the production phase. This approach enables the fermentation to approximate a quasi-steady state, where growth and production rates are stabilized over successive cycles. The cyclic strategy is particularly advantageous for long-duration processes or those involving slow-growing organisms, as it mitigates nutrient depletion and toxic metabolite accumulation.

Overall, fed-batch systems enhance control over fermentation dynamics, making them indispensable in industrial biotechnology and pharmaceutical manufacturing.