The influence of the configurations of multiple-impeller on canrenone bioconversion using resting cells of Aspergillus ochraceus

Abstract

11 α-Hydroxycanrenone is a key intermediate in the synthesis of eplernone which is a drug that protects the cardiovascular system. It can be obtained by microbial transformation of canrenone using Aspergillus ochraceus. The impeller configuration has a great impact on the microbial transformation efficiency. In this study, three kinds of multiple-impeller including six-blade Rushton turbine (lower) and six-blade Rushton turbine (upper) (RT + RT), six-blade Rushton turbine (lower) and six-arrow blade turbine (upper) (RT + ABT), six-blade Rushton turbine impeller (lower) and six-blade Chemineer CD6 impeller (upper) (RT + CD6) were employed to carry out the microbial conversion process, which was investigated by experiments and computational fluid dynamic (CFD) simulations. The CFD simulation was performed only for the hydrodynamic part of the bioreactor in this article. The results showed that RT + CD6 gave better conversion ratio compared to the other two multiple impellers. It had higher axial flow and better air volume fraction distribution which was benefit for the biotransformation process. A certain amount of cell content should be guaranteed in order to obtain a good substrate conversion (45 % approximately). The final conversion ratio of canrenone was proportional to the content of mycelium at the late stage of conversion, while the content of mycelium at the early stage had a subtle effect. Besides, A. ochraceus resting cells could tolerate the maximum and average shear strain rate in the order of 2598 s−1 and 52 s−1, respectively. The research results provided a guide for the selection of impeller for the biotransformation of canrenone in biopharmaceutical industry.