Microfluidic flow confinement to avoid chemotaxis-based upstream growth in a biofilm flow cell reactor

Introduction of a bacterial inoculant into a chemostat bioreactor can lead to unwanted contamination of upstream elements via chemotaxis. This can result in biofilm growth in connective tubing, valves and even the medium source reservoir itself, thus complicating the conditions of the applied liquid phase and impeding proper chemostat functionality. Applied to biofilm forming Pseudomonas fluorescens bacteria, we tested two different microfluidic flow confinement methods designed to impede upstream contamination. The first isolated biofilm growth from the relatively stagnant zones within the microchannel corners, and in the second a flow enhancement element was introduced to increase flow velocities and shear forces. Both methods showed improvement over a control design, but flow enhancement showed the best performance by delaying or preventing bacterial contamination of upstream elements, ensuring stability of the applied liquid media conditions for the entire duration of the experiments. This simple passive element has the potential for wide use as it is easy to implement and can be optimised for different experimental requirements.