Development of CFD models for simulating stem cell cultivation bioreactors

This thesis focuses on the simulation and modeling of flow, mixing, and transport in bioreactors using computational fluid dynamics (CFD), specifically in the context of bioreactors for the proliferation and specialization of stem cells for the production of cultivated meat. Conventional meat production is associated with various problems, including fatal infections, greenhouse gas emissions, land and water consumption, waste production, and antibiotic resistance. As a sustainable and ethical alternative, cultivated meat has gained attention. Plant-based products and cultured meat offer alternatives to conventional meat production, with cultured meat being produced through biotechnological processes in a laboratory. Stirred tank bioreactors are commonly used for both stem cell proliferation and specialization, and they play a crucial role in achieving scalable and economical cultured meat production. To assess the advantages of cultured meat, its environmental impacts are compared to those of conventional meat production. Cultured meat shows significant reductions in greenhouse gas emissions, water consumption, and land use, although it tends to be more energy-intensive. Social aspects and public acceptance are also considered, including security assessments, regulatory policies, and potential economic benefits associated with the cultured meat industry. Challenges such as social acceptance, organoleptic characteristics, and production costs need to be addressed to ensure the successful commercialization of cultured meat. The thesis primarily focuses on the first step of the cultured meat production chain, which involves the proliferation of stem cells in a stirred tank bioreactor. A computational model is developed to study a laboratory-scale bioreactor for stem cell proliferation. The work involves the creation of a single-phase simulation to validate the model predictions and gain insights into the bioreactor's behavior. This analysis includes a first step of grid independence based on the power consumption results,shear rate and mixing index evaluation. Subsequently, a multiphase simulation is performed, for two different geometries, to include both the liquid and gaseous phases, with the gaseous phase consisting of individual bubbles, with a constant diameter, introduced through a sparger. The simulations provide, besides the parameters previously cited, estimations of gas holdup, specific surface area, and mass transfer coefficients. Moreover, it is conducted a fluid-dynamic study of the inside of the bioreactor based on the observation of recirculation phenomena and cavities formation behind the impeller blades to obtain a regime map. Overall, this thesis contributes to the understanding of flow, mixing, and transport in bioreactors for stem cell proliferation in the production of cultured meat. The findings can inform the design and optimization of bioreactor systems, ultimately advancing the development and scalability of sustainable cultivated meat production.