There are many different types of bioreactors including: stirred-tank, rocker, air lift, and fixed-bed.
Traditional multiple-use bioreactors require cleaning after each cell culture run. Smaller-scale bioreactors are glass systems and can be sterilized in an autoclave. Larger bioreactors are stainless-steel systems that require additional plumbed-in systems for sterilization, such as cleaning in place (CIP) and steaming in place (SIP).
Single-use bioreactors were introduced into the biopharmaceuticals market around 25 years ago. They are made of single-use, closed, gamma-irradiated biocontainers, fitting on reusable hardware. Single-use bioreactors are increasingly used for small-scale, mid-scale, and large-scale production runs given their many benefits.
Stirred-tank bioreactors are equipped with an impeller for homogenizing culture media and a sparger for delivering oxygen to the cells. Stirred-tank reactors (STRs) are the most widely used bioreactors. These range in size from 15 mL to 2000 L for single-use and are available in sizes larger than 2000 L for stainless-steel. STRs are primarily used to scale up a process from research and development scale to manufacturing scale. The goal is to ensure that a process at a smaller volume can be representative of larger volumes. In addition to scale-up capacity, other key elements to consider are usability and process assurance of the single-use STR at the manufacturing scale.
Rocker bioreactors are offered as single-use systems. They involve a bag on a moving platform and relies on a rocking motion for the mixing. Oxygen diffuses through the headspace via liquid-gas interface, as these bioreactors are not equipped with a sparger. These bioreactors are typically smaller-scale, ranging from a few liters to a maximum 100 L. They are usually used for small-scale production or for seeding into larger bioreactors.
Air lift bioreactors are less frequently used in the biopharmaceuticals industry due to them being lesser known with regulatory processes that are largely unexplored. They rely on air bubbles to aerate and carry the media around the reactor for mixing at the same time.
Fixed-bed bioreactors are used for adherent-cells, involving specialist cells that can only grow when attached to a surface. They usually have strips of fibers (carriers) resulting in a high surface area for the cells to adhere to. These carriers are packed together to make the fixed bed. Aerated culture medium circulates through it. Adherent cells can also be cultivated as suspended cells in stirred-tank, rocker, and air lift bioreactors. However, they need to be attached to 100-micrometer beads (i.e., microcarriers) and put in suspension. Scale up of this process is much more complex and time consuming than the equivalent suspension process or the adherent-cell process in the fixed-bed bioreactors technology.