Packed bed or fixed bed bioreactors are used for culturing adherent or anchorage dependent cells in a 3D environment. Packed bed bioreactors provide more surface area vs other traditional methods such as roller bottles or t-flasks which makes it the bioreactor for culturing massive amounts of adherent cells. he cells are immobilized within macrocarriers which are fixed within the bioreactor vessel.
In any aerobic cell culture, there are two requirements for cells to grow and multiply properly: Nutrient and Oxygen. Nutrient is supplied to the cells through culture medium wherein the fixed bed is continuously submerged in. On the other hand, oxygen is supplied by dissolving oxygen into the medium and then supplying it along with the nutrients.
Packed-bed bioreactor is an efficient system for producing secreted products since the desired product can be harvested along with the media while the unnecessary cells are left behind, making downstream processing easier and less costly. Using a packed-bed bioreactor also protects cells from shear stress. The main challenge however of packed-bed bioreactors is the way that oxygen is supplied.
Oxygen transfer in these packed reactors occur in two steps: air to culture medium then culture medium to cells. This two-step transfer can limit the oxygen intake of cells, thereby inhibiting cell growth and limiting up-scale capability. Also since the media is circulated only in one direction, oxygen distribution is uneven, with one end of the packed bed having very rich oxygen supply while the other end has little to no oxygen supply. This set up might result to hindered cell growth or even cell death.
The Tide Motion System overcomes oxygen limitation via its dual oxygenation scheme. First, the tide motion principle allows the direct exposure of cells to oxygen, allowing direct transfer of oxygen from the air to the cells themselves. Second, even during the nutrition phase of the tide motion, cells are still able to intake oxygen, via the dissolved oxygen in the culture medium. This dual oxygenation allows the linear scalability of the TideXcell™ up to 5,000 L.