The Examination of Bioreactor Heterogeneity with Rheological Different Fermentation Broths

Abstract

Bioreactor heterogeneity has been studied in a pilot scale airlift reactor (0.3m3), which is multiconfigurable creating different degrees of heterogeneity. Hydrodynamic and oxygen transfer performance of two ring sparger configurations, annulus and draft tube, in combination with a marine propeller fitted at the base of the reactor, are compared using Newtonian baker’s yeast and non-Newtonian Saccharopolyspora erythraea broths. In aerated only systems, cells experience a heterogeneous dissolved oxygen environment with both Newtonian and non-Newtonian fermentations. The use of the marine propeller when used in conjunction with the annulus sparger to draw liquid down the draft tube, was found to produce significant increases in the hydrodynamic and oxygen transfer performance of the vessel. This resulted in reduced dissolved oxygen heterogeneity with both fermentation broths, and increased erythromycin production from S. erythraea. The relationship between superficial gas velocity and gas holdup for different morphological S. erythraea fermentations were found to be significantly reduced when compared to Newtonian yeast broths, but similar to yeast when propeller and aeration operation was compared Thus the effect of morphology, rheological properties and reactor design on overall reactor performance has been demonstrated.