Details

Autor(en) / Beteiligte

• Rasheed, Fayaz

Titel

Shear Flow Experiments Toward the Development of a Containerless Bioreactor

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

2018

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• Manned space missions of the future will require great self-sufficiency, due to their long duration. A bioreactor onboard a spacecraft or the International Space Station (ISS) can help achieve self-sufficiency for culturing microorganisms to support gut microbiome or grow cells and tissues for medical and research purposes. A bioreactor can also be used for culturing plant growth-promoting bacteria (PGPB), and growth and development of plant protoplasts. Unlike bioreactors with solid walls, a containerless bioreactor in microgravity, in which fluid containment is achieved by surface tension, is advantageous since it readily allows the exchange of gases. Such a bioreactor can be an extension of the ring-sheared drop (RSD) module designed to study shear-induced amyloid formation onboard the ISS, where a 25 mm diameter drop of protein solution will be contained by surface tension and constrained by a pair of sharp-edged tubes, forming two contact rings. Shear in the RSD is imparted by one tube rotating relative to a stationary tube, through the action of surface shear viscosity. To establish a fundamental understanding of shear response, knife edge experiments, where a rotating tube shears the air-water interface with an insoluble monolayer (stearic acid), was used. Shearing was performed under the condition of steady and oscillatory (sinusoidal) forcing, at various Reynolds numbers and Stokes numbers. In the steady flow case, the non-dimensional velocity profiles showed very low dependence on Reynolds number. The oscillatory flow was vital since it enhances mixing, compared to a steady flow. The phase lag in the interfacial velocity near the knife edge in the oscillatory case, at various Reynolds and Stokes numbers, were measured. The phase lag became steeper with increasing forcing frequency and amplitude, and the response of the oscillatory forced system was found to be more sensitive compared to steady. The second set of experiments were performed involving interfacial shearing of protein solution contained in a cylindrical dish, again using a knife edge. Here the fibril formation of protein (human recombinant insulin) with shear and the decrease in concentration of native protein solution with time was studied. The ability of native protein monomers to transport to the interface and be adsorbed to the interface is found to be crucial to shear-induced fibrillization phenomenon. The knife edge protein shearing experiment serves as an analog to the ring-sheared drop experiment onboard the ISS, where the solution of protein in the dish has a similar surface area to volume ratio as the ring-sheared drop experiment. The results and conclusions made from this dissertation are a major step in understanding the science and behavior of fluids under interfacial shear for the development of a containerless bioreactor in space.