HRBR for Adherent Cultures Using 3D Porous Carriers

A moving packed bed bioreactor for cell cultures

Highlighting another patented system based on the patented HRBR technology platform, this packed bed bioreactor is designed for the application of adherent cultures using 3D porous carriers made of ceramic, polyester fiber, polyurethane fiber, etc. The culture vessel of this system features:

• One large special baffle which is tightly sealed to all three contact surfaces of the culture vessel so that the culture medium does not leak through the baffle during the entire rocking process.

• Two sets of two gas ports configured and controlled to allow the respiratory gas to flow in and out through one set while always retaining the gas flow above the liquid phase so that the liquid loading capacity is maximized and no foaming issue created.

• One perforated partition forming a compartment to hold the 3D fibrous carriers as a moving packed bed bioreactor, with which the direct contact of cells in the gas phase can be performed like a roller bottle system than through the bulk liquid phase like in most conventional system, for the best efficiency of oxygenation with minimal shear stress to the cells. 

• The unique moving packed bed enables to easily regulate the concentration of key substrate during the entire culture process to a limiting level which often significantly induces the protein expression for the maximum specific production of biologics.

Packed Bed Bioreactor (PBBR) systems have many advantages over microcarrier systems for adherent cell cultures in terms of cell attachment, medium replacement, and high cell density. In recent years PBBR systems have therefore gained significant popularity for adherent cell cultures. PBBR systems have also served as excellent devices for perfusion cultures because they do not require an external and unreliable cell retaining device.

HRBR is a new class of packed bed bioreactor which overcomes the drawbacks of the current conventional fixed bed bioreactors represented by Eppendorf’s (formally NBS) Celligen Plus and Pall’s iCellis bioreactors which use 3D fibrous carriers to form a fixed packed bed for cells to adhere and grow and apply the pumping effect of an impeller to promote the mixing and aeration. The popular Eppendorf’s (formally NBS’) Celligen plus bioreactor is the pioneer of the packed bed bioreactor using high surface area 3D fibrous carriers to perform high cell density cultures. Both Celligen plus and iCellis systems require high pumping and circulation rate to achieve the sufficient oxygenation but with less efficiency of submerged aeration particularly when the size of bioreactor increases. This also equates to increased shear stress and difficulty of scale up. Another exceptionally desired feature is the ability to easily regulate the concentration of key substrate during the culture process to a limiting level frequently which can often significantly induce the protein expression for maximum specific production of biologics. None of these conventional bioreactors can achieve this objective easily without sophisticated control scheme.

This innovative system uses extremely low rocking (2-3 rpm) from 0 to 180 degrees angle without agitation or pumping using impeller to significantly reduce shear stress while providing excellent mixing using a specially designed baffle and unique gas flow control. Most extraordinarily, this system enables to utilize the moving packed bed performing the unparalleled efficient aeration based on the unique roller bottle principle (see video below) by the direct intermittent aeration of cells in the gas phase rather than through the bulk liquid phase like most conventional bioreactor systems. This inventive bioreactor possesses all characteristics of high cell density fixed packed bed bioreactors but provides superior oxygenation scheme with little to no shear stress to alleviate their limitation of scaling up to large production scale. It is capable of applying the easiest and most effective approach to regulate the substrate concentration to a critical limiting level for maximizing the protein expression. This new class of bioreactor system not only revolutionizes the conventional system for its simplicity in design and configuration but also creates an unparalleled low shear stress environment and enables to apply the unique oxygenation method in all scale of operations, making scale up very easy. As a result of not using an agitator, it is easier to place a bag inside of the vessel adapting it into a single use bioreactor which has gained great popularity in the industry.

How Does it Work?

• Use of a special baffle design: a large baffle is sealed to all contact surfaces assuring little or no leakage of fluid through the baffle contact points and only over the top of it as the vessel rocks. This assures potent mixing with very little shear force. Every rock of the vessel yields 2 complete "turn-overs" of the entire fluid contents of the vessel.

• Two sets of gassing ports alternately controlled to assure that gas passage is in the gas phase for surface aeration as the liquid contents falls over the baffle. The surface aeration avoids foaming concerns.

• The 3D carriers with high surface area are held in the compartment confined by a perforated screen in a section of the vessel. As the vessel is rocked/rotated in 180 degrees,  the cells embedded in the carriers are exposed to air and submerged to the medium intermittently as a roller bottle operation and perform the most efficient and simplest oxygenation.