The paddle mixing system has classical probes with a transmitter, while orbital shaking and stirred mixing bioreactors have
optical probes. Optical probes were more stable because they took a measure every five seconds. Bioreactors with disposable
probes have a mixing time higher than traditional bioreactors because disposable probes have a higher response time compared
to traditional ones. Classical probes were less stable and showed variations of around 0.03 pH unit even a few minutes after
Mixing times on all disposable bioreactors were above traditional bioreactors. For the stirred mixing bioreactor, the mixing
time was close to one minute, which is recommended for mammalian cell culture.1 Orbital shaking and paddle mixing were below two minutes.
Nevertheless, after sodium hydroxide injection, pH measured stayed or remained below or close to the final pH value. Even
if the mixing time were longer than usual, cells would not be subjected to high feed or sodium hydroxide concentrations during
Temperature mapping. Temperature mapping was performed because bags could be heated either by a jacket or by a blanket. Thus the temperature mapping
allowed for assessing the efficiency and homogeneity of each heating system. It was measured in water at the maximum working
volume and the agitation speed applied during production process. Temperature set points applied were from room temperature
to 37 °C and from 37 °C to 29 °C (see Table 4).
Table 4. Comparison of temperature mapping measured between disposable bioreactors
Bags are in plastic, which does not conduct heat efficiently. Jackets provided higher temperature performances than blankets
but also generated temperature gradients inside bags during heating and cooling activities.
The water inside the paddle mixing bioreactor jacket was from a water bath. When the system heats, the water bath is at 60
°C, so the temperature inside the bag can be 3°C above the set point. With this equipment, a 0.8 °C difference has been noticed
between equipment temperature probe and calibrated Merck Serono temperature probes.
Merck Serono Biodevelopment performed a four-month study to evaluate disposable bioreactors. Different mixing principles were
assessed in a disposable bag for seeding and fed-batch production processes. Process performances were similar to 250 L seeding
bioreactors, 1,250 L production bioreactors, and 3.6 L process development bioreactors. Either cell growth, viability, molecule
concentration, or quality were quite similar between bioreactors. Bioreactor characterization showed points to be improved
in terms of probes and heating system.
During this project, MSB managed to set up a bioreactor in less than 30 minutes. Within three months, 11 runs were performed
without any internal equipment validation or qualification. No contamination was observed despite filling and removing liquid
several times in the bag. Disposable bioreactors were easy to manipulate and changed cell-culture process down time.
Aurore Poles Lahille is an assistant scientist, specialist new technologies, Richard C is a process specialist, Fisch S is USP production technician, Pedelaborde D is an equipment specialist, Gerby S is a trainee ENSTBB, Perrier V is head of the process development unit, Balbuena D is a process development and QC manager, Trieau R is head of the process improvement unit, Valognes L is the production manager, Peyret D is director of Merck Serono Biodevelopment, all at Merck Serono Biodevelopment, Martillac, France, email@example.com
+33 (0) 557 960 960.
1. Riba JP. Réacteurs enzymatiques et fermenteurs. Traité Génie des procédés, Technique de l'ingénieur. 1998.