Multiphase microreactors with intensification of oxygen mass transfer rate and mixing performance for bioprocess development

This research is focused on the development of a borosilicate glass-based microbioreactor (MBR) to address two of the challenges that MBRs may be confronted with: poor mixing and mass transfer limitations. To overcome these challenges, a microbubble column-bioreactor (μBC) for biotechnological research was developed and characterized. Pressurized air was supplied through a nozzle (hydraulic diameter 26 μm) at the bottom of the μBC (reactor volume 60 μL). The airflow was accelerated, generating a continuous stream of microbubbles that rose through the μBC. This investigation describes the hydrodynamic and mass transfer characterization of the μBC. The aim of the study was to prove that the pneumatic aeration through a micro nozzle provided sufficient aeration to satisfy the high demand of oxygen of aerobic bioprocesses, and at the same time, it enabled the homogenization of the cultivation broth and avoided the cell sedimentation. For this, the influence of the superficial gas velocity on the volumetric liquid-phase mass transfer coefficient is shown as well as the influence on other mass transport-related parameters, e.g. gas hold-up, Sauter mean bubble diameter, bubble rise velocity, superficial liquid velocity, volumetric power input, and mixing time. Additionally, a simplified computational fluid dynamic model was developed as a complement to this experimental research. The model serves as a supporting numerical tool to estimate the fluid dynamics inside the μBC.