Abstract
Control of dissolved oxygen tension (DOT) in stirred tank bioreactors (STB) is commonly performed by manipulation of gas flow or agitation. However, control systems using this strategy directly alter hydrodynamic conditions thus interrelating oxygen and momentum transfer effects in the culture. The aim of this study was to develop and evaluate an alternative DOT control system using an algorithm that allows further study of oxygen and momentum transfer effects separately. A novel algorithm was designed with three mass flow controllers by manipulating oxygen partial pressure The developed system tightly controlled DOT at 30% in a 3-L bioreactor with Escherichia coli, maintaining constant gas flow and agitation. The energy dissipation rate (EDR) by agitation was maintained at 0.06 W/kg, and EDR variations via bubble wake and bursting were diminished. The accumulated DOT control error was 42% lower than that of a standard commercial controller. Additionally, the system effectively responded to perturbations on set point (30, 50, and 80%) and agitation (200, 500, and 1000 rpm). To the best of authors’ knowledge, this is the first characterization of a DOT controller in terms of EDR and control error that could be used to study oxygen and momentum transfer effects separately in STB.
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