Bioprocess Operation Modes: Batch, Fed-batch, and Continuous Culture

Overview

Feed automation

Perfusion

The addition of nutrients and removal of by-products to and from the culture medium, respectively will affect the cell density and viability, the bioprocess duration, and as a result, the product titer, yield, and cost. This is true for cell culture in bioreactors as well as microbial cultures and is why optimizing the nutrient supply is key in bioprocess development . To help with this, different bioprocess operation modes have been established with varied substrate feeding strategies suited towards particular bioreactor cultures. The main bioprocess operation modes include batch culture, fed-batch culture, continuous culture, and perfusion culture – a type of continuous culture. Here you can find guidance on batch, fed-batch, and continuous culture operation modes, including the advantages and disadvantages, and how to set up the respective bioprocesses.

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What are the differences between batch, fed-batch, and continuous culture?

Read more about the differences between batch, fed-batch, continuous, and perfusion culture and learn more about advantages and disandvantages of the different bioprocess modes.

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Batch culture‌

Fed-batch culture‌

Continuous culture‌

Perfusion culture‌

Perfusion culture is a type of continuous culture where cells are retained or recycled back into the bioreactor. Similar to other types of continuous culture, nutrients are replenished, and toxic by-products are removed to keep the culture in a steady state.

Advantages

Steady state cultures can be maintained for up to several months to reduce the culture downtime
High cell densities - and subsequently high yields and volumetric productivity can be achieved
Due to higher volumetric productivity the working volume and therefore equipment footprint can be reduced, compared to batch or fed-batch processes

Disadvantages

Process operation is more challenging than in batch or fed-batch processes
Increased risk of contamination due to the extended duration and continuous feeding and harvesting
Limited traceability, as the culture suspensions aren’t harvested in batches

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Which bioprocess mode is best suited for your application?

You would like to cultivate your cells or microorganisms in a bioreactor but are unsure which process mode to use? In our “Beginners’s Guides Bioprocess Modes” we explain the differences between batch, fed-batch, and perfusion bioprocesses and how to select the right process mode for your needs. We guide you through a complete bioprocess, including inoculum preparation, bioreactor setup, sensor and pump calibration, culture feeding, and sample analysis throughout the run.

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Downloads

Application note

A Beginner’s Guide to CHO Culture: Bioprocess Modes– Batch, Fed-Batch, and Perfusion

PDF 1.8 MB

Application Note

A Beginner’s Guide to E. coli Fermentation: Bioprocess Modes – Batch, Fed-Batch, and Continuous Fermentation

PDF 1.9 MB

How can feed automation improve bioprocesses? And what is required to establish automated feeding?

Sensor integration

Feed automation can have several benefits in upstream bioprocessing. It reduces manual workload, prevents nutrient depletion, creates a more stable culture environment, and improves yields and standardization. To do so, the metabolic status of the culture and/or nutrient concentrations in the culture medium need to be continuously monitored in real-time. In-process monitors are implemented into bioreactor control systems for the calculated and automated adjustment in feed rate, via the use of feed pumps. Learn more about the integration of sensors with bioprocess control systems.

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Strategies for feed automation

There are different strategies to automize culture feeding. In a time-based strategy a defined volume of feed solution is added to the culture per time increment. In a sensor-based feeding strategy, a feed solution is added based on a sensor reading. Feed automation can be achieved through monitoring of several different parameters, including the concentration of the substrate (e.g., glucose) itself or the dissolved oxygen (DO) concentration or the respiratory quotient (RQ), which are influenced by the metabolic state of the culture. The Eppendorf bioprocess control software packages DASware® control and BioCommand® facilitate the implementation of tailored feedback control loops for feed automation. Learn more about Bioprocess Feed Automation Enabled through Software Scripts in our ebook.

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Application examples for automated culture feeding in fed batch bioprocesses

Perfusion cell culture: What are cell retention techniques for perfusion culture and which devices can be used for these?

Perfusion processes can deliver more product for a given bioreactor volume as they can maintain higher viable cell densities than traditional fed-batch processes. Smaller bioreactors can be used, saving precious lab space. Cell retention is an essential aspect of perfusion culture. It is used to maintain high cell densities while harvesting media and removing by-products, and can be achieved using several different techniques, including:

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Filtration using spin filters‌

Tangential flow filtration (ATF and TFF)‌

Packed-bed bioreactors‌

Packed-bed bioreactors are filled with a solid growth support on or in which the cells are immobilized. One such support are Fibra-Cel® discs . Fibra-Cel is a porous meshwork of polyester and polypropylene that provides a growth surface for adherent cells and entraps suspended cells. Immobilization of cells in the matrix facilitates the easy harvest of cell-free medium from the bioreactor. Furthermore, Fibra-Cel^® offers a high surface to volume ratio and protects cells from damaging shear forces.

Learn, how packed-bed bioreactors were used for the cultivation of anchorage-dependent Vero cells in perfusion.

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Cell-Lift impeller with decanter column‌

Cell-Lift impellers with decanter columns can be used for perfusion cultivation of cells grown on microcarriers. Cell-Lift impeller rotation creates a negative pressure in the hollow impeller tube causing medium to circulate uniformly in a closed loop. Cells and microcarriers are separated from the medium in the decanter column. The medium is harvested and the cells and microcarriers are transferred back to the bioreactor. Advantages of this system include reduced shear force, high mass transfer of nutrients, and a high oxygen transfer rate.

Many glass and stainless-steel bioreactors from Eppendorf can be equipped with Cell-Lift impellers and decanter columns, including benchtop BioFlo® 320 bioreactors and the CelliGen 510 sterilize-in-place bioprocess system .

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Learn more about the functioning of Cell-Lift impellers with decanter column and how it was used for cultivating Vero cells on microcarriers in perfusion.

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Bioprocess Operation Modes: Batch, Fed-batch, and Continuous Culture