Given the many mixing technology options available and the variety of applications, it is important to get feedback from end-users.
Keeping this in mind, we interviewed several end-users to see if there are some general messages that need to be addressed
by the suppliers.
When considering mixing technologies, it is important to consider the application. We interviewed a German contract manufacturer
who has been testing disposable mixers (5–200 L) for the last 18 months for ultra and diafiltration applications used in the
GMP manufacture of a human therapeutic protein. They tested the Millipore Mobius system, the LevTech system, and the ATMI
Padmix system. The LevTech system was not retained because of the startup time. "If an operator accidentally switched the
system off, we would lose an hour's production time," said the manufacturer. Although the ATMI Padmix system provided robust
mixing, it was not retained because of the room height required to fit in the paddle for a 200-L system. The system that best
fitted their requirements was the Millipore Mobius because it "works efficiently, is virtually particle free, is not cumbersome,
and takes less than five minutes to set up."
Another end-user selected the ATMI Padmix system for solid-liquid applications because it works efficiently for even the most
difficult mixing applications. Contained powder transfer is also a nice feature of this system. According to this end-user,
the drawbacks of the system are the ceiling height requirement because of the overhead impeller and certain manipulations
of the paddle.
The beauty of the LevTech technology as seen by end-users is that the levitating technology ensures there is virtually no
particulate generation, which makes it the technology of choice for late-stage downstream processing applications. This also
makes it useful for final formulation applications in vaccine manufacturing, when a final sterilizing filtration step may
not be possible. The technology is suitable for a majority of powder-to-liquid applications, although the set up time for
charging the superconductors (40 minutes) is not accommodating to the fast turnaround required in media and buffer preparation.
A veterinary vaccine manufacturer tested both the Padmix and the Hyclone Single-Use Mixer for a viral inactivation step and
found the ATMI Padmix very simple to use and liked the fact that it is a completely contained system. Another factor that
contributed to this end-user's choice of the Padmix was that the mixer driver can be decoupled from the bag container allowing
interchanging of containers. This end-user considers that disposable mixing systems have considerably matured over the last
two years but durability and integrity of the bags can still be an issue.
A major US contract manufacturer tested several mixing systems for blending chromatography column loads. In this case, they
chose the Xcellerex XDM Quad Mixer working at 500-L scale. The selection was based on ease of use, mixing efficiency, and
the fact that it is an all disposable impeller and that the system is reasonably priced.
The last interviewee, a veterinary vaccine manufacturer in France, indicated that they had tested several disposable mixing
systems since 2003 for final bulk formulation working with aluminium gel hydroxide. This was a difficult mixing application,
in which the product had to be maintained in a sterile condition because there was no downstream sterilization before filling.
They tested the Wave Mixer, LevTech Mixer, Stedim Flexel 3D recirculation system, Millipore's Mobius, and ATMI's Padmix. The
Padmix provided robust mixing but was apparently difficult to set up and the LevTech technology was efficient but the length
of start-up time was a major drawback. The company selected the Millipore Mobius Mixer because of the plug-and-play nature
of the technology along with the particle-free nature of the mixing system.