Design and development of components of a modular bioreactor

Abstract

Biologic drug manufacturing is traditionally conducted in large-scale, industrial bioreactors. The emergence of interest in disposable, bench-top bioreactors as a viable alternative is due to potential advantages such as lower contamination risk, time and cost savings, and ease of handling. The challenges associated with disposable, bench-top bioreactors include poor mixing, limited oxygen transfer, and a scarcity of non-invasive sensors for process control. This thesis investigates multiple aspects of a disposable, perfusion-capable bioreactor, in order to facilitate an optimal design. In order to determine an impeller configuration that improves the mixing and mass transfer characteristics of a i-liter bioreactor, Computational Fluid Dynamics (CFD) was used. The potential benefits of switching to a dual-Marine impeller system was revealed, which was then validated during fermentation experiments. Further predictions of a merging flow pattern in the i-liter vessel was consistent with the literature based on the impeller spacing. A scaled-up 5-liter vessel was designed with Rushton impellers spaced so as to create a parallel flow pattern, which was later successfully predicted in the CFD simulations. Flow patterns were analyzed at various locations in both vessels to aid future design iterations. Monitoring of process parameters, including liquid level, is important for automated control in bioreactors. Three novel, non-invasive, optical liquid level sensing methods were conceptualized, prototyped, and successfully tested. These solutions relied on self-developed image processing algorithms. Additionally, a magnetic liquid level sensor was also developed and tested that relied on a magnetic float and a series of reed switches. In order to increase the perfusion membrane surface area and reduce complexity, the switch to a hollow-fiber harvest probe was examined. CFD studies guided design iterations by modeling the flow around the probe, giving insight into the stagnation properties and shear forces acting on the fibers. Additionally, experimental testing of the new harvest probe revealed its successful functionality and viability in the bioreactor.