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Cell culture conditions

Cell culture is a major technique in biotechnology and the life sciences that describes removing cells from animal or plant sources and growing them in an artificial environment. For optimization of growth and proliferation of cultured cells, it’s important to maintain basic environmental requirements. Though cell culture conditions vary largely depending on cell types, the artificial environment invariably comprises:

  • A cell culture medium to supply nutrients like carbohydrates, amino acids, vitamins, and hormones
  • Required gases, usually oxygen and carbon dioxide
  • Controlled temperatures

Other requirements are to keep the pH and osmotic pressure within the limits of the specific cell line. Classified as anchorage-dependent, adherent cells require an attachment substrate like microcarriers to grow, while nonadherent ones simply grow in suspension culture.

Bioreactors vs fermentors

Cell cultivation can occur in a broad variety of vessels, including tissue culture dishes, shake flasks, and T-flasks. However, to improve productivity and ensure reproducibility of results from batch to batch for biologic manufacturing, sophisticated systems such as bioreactors and fermentors are used.

Bioreactors support the growth of various cell types that require oxygen, such as mammalian cell lines and insect cells. On the other hand, fermentors allow for the proliferation of microorganisms such as bacteria, yeasts, and fungi. Both fermentors and bioreactors control key parameters for cultivation, including temperature, agitation, and gases.

Types of bioreactors

There are various types of bioreactors, including fixed-bed, rocking, air lift, and stirred tank bioreactors. Some are made of materials that require sterilization after each cell culture process. Small-scale models are often glass systems that can be sterilized in an autoclave.

Larger systems can be categorized as stainless steel bioreactors and single-use bioreactors. Stainless steel reactors require plumbed-in sterilization systems, as they must be cleaned between runs. Single-use bioreactor systems are designed for use with presterilized plastic biocontainers, tubing assemblies, and other single-use components that are discarded after each run. Single-use bioreactors help limit contamination and support use in small-, mid-, and large-scale production.

Stirred tank reactor FAQs

Here are answers to some frequently asked questions.

What are stirred tank bioreactors?

Stirred tank reactors are culture vessels with motor-driven central shafts that support one or more agitators or impellers. They are commonly used to cultivate cells to produce biologics such as antibodies, enzymes, vaccines, and viral vectors.

What is their function?

Stirred tank bioreactors are often used to maintain a uniform physicochemical environment during cell culture processes and to obtain representative cell samples. They allow easy scale-up, optimal fluid mixing, and oxygen transfer. These systems employ mechanical agitation through an impeller to disperse all compounds and achieve a homogeneous concentration.

What are the essential components of a stirred tank reactor?

Basic features of a stirred tank bioreactor include:

  • An agitation system with impellers
  • An oxygen delivery system
  • A foam control system
  • A temperature management system
  • A pH control system
  • Sampling ports
  • A sump and dump line to empty the reactor
  • A cleaning and sanitization system if using stainless steel bioreactors

Cytiva’s stirred tank bioreactors for mammalian cell culture

Xcellerex™ single-use bioreactors are used in many biomanufacturing applications, including:

They can be operated in batch, fed-batch, or perfusion cell culture modes.