Bioprocess improvement by design-modified bioreactor flow properties

Abstract

The aim of this study was to achieve bioprocess intensification by bioreactor flow field improvement. Two component properties of the flow field, namely, flow and shear are represented by two macroscopic mixing characteristics - impeller pumping capacity, Fl, and rate of kinetic energy dissipation, ε. Mixing rates are affected by impeller design and may be the result of a design-imposed flow modification of characteristics, e.g. higher or lower bioreactor circulation and/or turbulence properties can be achieved. The results illustrated that two basic impeller types - a modified flat-blade and modified inclined blade, could tailor a stirred bioreactor flow field in a pre-selected style. The design modification was aimed at higher oxygen transfer via increased ε or improved ε-distribution in the bioreactor bulk. Zones of different ε were revealed, implying different oxygen tension and bioreaction intensity. For the sake of prognostic evaluation, the mass transfer coefficient kL was determined. The designs of slotted flat and inclined blades were found to be prospective in terms of energy efficiency and can be recommended for design retrofitting of existing bioreactors.