(283g) 3D-Printed Continuous Stirred Tank Mini-Reactor (CSTmR) for Cell Culture Applications

The use of miniaturized reactors for bioprocess development is a promising field, as mini-bioreactors may facilitate and expedite the development and optimization of high-value bioprocesses, such as those performed in the pharmaceutical industry. In addition, the availability of simple, cost-effective mini-bioreaction platforms will greatly contribute to the democratization of biological research. Despite this promise, only a limited number of mini-bioreaction systems are commercially available, and those in existence are prohibitively expensive. Moreover, the in-house construction of miniature devices is often challenging and time consuming.

Here, we describe the design, fabrication, and use of a miniaturized bioreaction platform that integrates a small, portable, do-it-yourself (DIY) incubation chamber for temperature control, a DIY mini-magnetic stirrer, and a 3D-printed continuous stirred tank mini reactor (CSTmR) with an effective volume of 2.5 mL. Our CSTmR features an off-center agitation system that enables homogeneous mixing even in the laminar regime, as demonstrated by tracer experiments and Computational Fluid Dynamics (CFD) simulations. Aeration is achieved by continuously injecting a filtered stream of O₂ into the reactor head space. Oxygen is produced by a portable oxygen generator used for medical applications. We show that this simple system can be used to perform aerobic bacterial culture experiments in both batch and continuous mode. Aiming to demonstrate the feasibility of using this inexpensive system to evaluate and optimize the growth conditions of cells of pharmacological interest, we cultured a recombinant Escherichia coli strain that was engineered to produce an influenza virus antigen. In batch culture mode, we conducted typical experiments to determine the kinetic parameters of the bacteria. These parameters were practically equivalent, in the experimental space explored, to those derived from experiments in 1-L fully instrumented bioreactors. In continuous culture experiments, we successfully achieved a distinct operational steady state at various flow rates.

The miniaturization approach presented here allows for reducing the volume of reagents used, concomitantly decreasing the economic investment during research and development (R&D) activities. This easily fabricated and operated DIY platform enables any lab to mount and operate reliable and reproducible bacterial culture experiments.