What are orbitally shaken bioreactors (OSRs) and why are they used?

Orbitally shaken bioreactors (OSRs) are systems designed to cultivate cells in a controlled, suspended environment. They are particularly useful in early-stage research and development for bioprocesses due to their simplicity and ability to gently handle sensitive cells like Chinese Hamster Ovary (CHO) cells. They offer a scalable solution for mammalian cell cultivation. However, scaling them up for large-scale production can be challenging, making optimization of their design crucial.

What are baffles in the context of bioreactors, and what purpose do they serve?

Baffles are structures incorporated into orbitally shaken bioreactors (OSRs) to enhance mixing efficiency and oxygen transfer. They work by modifying the flow field within the reactor. The strategic placement of baffles can significantly impact key parameters such as mixing efficiency, oxygen transfer rate, energy transfer, and shear stress. Optimizing baffle design is crucial for improving cell cultivation.

What is Computational Fluid Dynamics (CFD), and how is it used in bioreactor design?

Computational Fluid Dynamics (CFD) is a valuable tool used to simulate and analyze fluid behavior within bioreactors. In the context of orbitally shaken bioreactors (OSRs), CFD allows researchers to virtually test different design parameters, such as baffle configurations, to predict their impact on mixing efficiency, oxygen transfer, and shear stress. This approach is faster and cheaper than physical prototyping, enabling the optimization of bioreactor designs for better cell growth.

What does 'mixing efficiency' mean in the context of bioreactors, and why is it important?

Mixing efficiency refers to how well the contents of a bioreactor are blended. In orbitally shaken bioreactors (OSRs), adequate mixing is essential for ensuring that cells receive a uniform supply of nutrients and oxygen. Poor mixing can lead to gradients within the reactor, affecting cell growth and productivity. Therefore, optimizing mixing efficiency is a critical consideration in bioreactor design.

What is 'shear stress' and why is it a concern in cell cultivation within bioreactors?

Shear stress is the force exerted on cells by the moving fluid within a bioreactor. High shear stress can damage sensitive cells, such as Chinese Hamster Ovary (CHO) cells, hindering their growth and productivity. In the context of orbitally shaken bioreactors (OSRs), it's crucial to design systems that minimize shear stress while maintaining adequate mixing and oxygen transfer. Optimizing these factors ensures a favorable environment for cell cultivation.

Mammalian cells growing in a baffled bioreactor with flowing oxygen molecules

Baffled by Bioreactors? How Optimized Shaking Can Revolutionize Cell Cultivation

Soraya Malik in Tech & Innovation December 2025 • 4 min read.

"Discover how baffled orbitally shaken bioreactors (OSRs) enhance cell growth and oxygen transfer, offering a scalable solution for mammalian cell cultivation."

In the world of biotechnology, cultivating mammalian cells is crucial for producing valuable substances, ranging from life-saving pharmaceuticals to industrial enzymes. Orbitally shaken bioreactors (OSRs) have emerged as a popular tool for this purpose, especially in early-stage research and development. These systems provide a controlled environment where cells can grow in suspension, making it easier to screen and develop bioprocesses. However, scaling up OSRs for large-scale production remains a significant challenge.

Traditional stirred tank reactors (STRs) are often used in large-scale cell cultivation, but OSRs offer a gentler approach that minimizes stress on sensitive cells, like Chinese Hamster Ovary (CHO) cells, commonly used in biopharmaceutical production. The simplified design of OSRs also makes them more attractive for scale-up. To improve mixing and mass transfer within OSRs, researchers have been exploring various vessel geometries. For example, disposable shaken tubes with conical bottoms and helical tracks inside the vessel walls have been designed to enhance oxygen transfer.

One persistent problem with OSRs is balancing adequate mixing with low shear stress. High shear stress, which can damage cells, often accompanies increased mixing. Therefore, there's a pressing need to design OSRs that can provide both efficient mixing and a stress-free environment for cell growth. Computational Fluid Dynamics (CFD) has become a valuable tool for evaluating and optimizing bioreactor designs. This approach allows researchers to predict fluid behavior and assess the impact of different design parameters. This article will dive deep into how CFD is being used to analyze a novel baffled OSR, offering new insights into improving cell cultivation.

How Baffles Boost Bioreactor Performance: A Deep Dive into CFD Analysis

Mammalian cells growing in a baffled bioreactor with flowing oxygen molecules

Researchers have proposed a new type of OSR incorporating a baffle structure. They used a three-dimensional CFD model to analyze how these baffles influence the flow field within the reactor. The key question was: how does the baffle structure affect mixing efficiency, oxygen transfer, and shear stress?

The CFD model allowed the team to test different baffle configurations virtually, which is faster and cheaper than building and testing physical prototypes. The simulations focused on the impact of baffle installation height on several critical parameters:

Mixing Efficiency: How well the contents of the reactor are blended.
Oxygen Transfer: The rate at which oxygen is supplied to the cells.
Energy Transfer: The amount of energy used to agitate the liquid.
Shear Stress: The force exerted on the cells by the moving fluid.

The results indicated that a lower installation height of the baffles was more effective at improving mixing efficiency. Compared to OSRs without baffles, the baffled design significantly enhanced oxygen transfer. Interestingly, the oxygen transfer rate was not significantly affected by the baffle installation height. However, as the baffle installation height increased, the energy transferred for liquid motion decreased. Most importantly, the proposed baffled OSR design created a gentle shear stress environment, which is beneficial for the growth of mammalian cells.

The Future of Bioreactors: Optimized Designs for Better Cell Growth

This research demonstrates the potential of using CFD to optimize bioreactor design. By carefully considering the placement of baffles, it's possible to create OSRs that provide efficient mixing, high oxygen transfer, and low shear stress—all critical factors for successful mammalian cell cultivation. While the current study provides valuable insights, future research should explore the impact of bubble behavior on shear stress, as this could further refine bioreactor designs. With optimized bioreactors, biotechnology companies can improve the efficiency and scalability of cell cultivation, leading to more cost-effective production of essential biopharmaceuticals and other valuable products.