Study On The Performance Of Canrenone Microbial Conversion Reactor

11α-hydroxycanrenone is a key intermediate in the preparation of eplerenone,which can be synthesized by 11α-hydroxylation of canrenone.In this study,at the level of shake flask and 1 L and 5 L bioreactors,canrenone was used as the substrate.A reasonable impeller structure was designed by Aspergillus ochraceus biotransformation,cold model experiment and computational fluid dynamics.The engineering characteristics and flow field characteristics of canrenone microbial transformation reaction were explored,and the relationship between them was discussed,which provided a reference for the industrial production of 11α-hydroxycanrenone.The main results of this study are as follows.（1）It can be seen from the shake flask,1 L and 5 L bioreactor experiments that the shear stress is crucial to the microbial transformation of canrenone.The results of shake flask showed that the conversion ratio of adding beads was higher and the conversion rate reached87.9%at 60 h.The results of 1 L bioreactor experiment showed that the slow gradient adjustment speed is more conducive to the biotransformation of canrenone.The higher the rotational speed,the greater the shear strength.And the rotational speed can be appropriately increased at 0-20 h in the early stage of biotransformation,and the rotational speed can be appropriately reduced after 60 h in the end of biotransformation.Through the 5 L bioreactor experiment,it can be seen that the number of blades and the diameter of the blades have a significant effect on the conversion of canrenone,and the six-blade impeller and the large-diameter impeller have better conversion effects.（2）From the resting cell transformation experiment,it can be seen that the six-blade Rushton turbine impeller（lower）and six-blade Chemineer CD6 impeller（upper）（RT+CD6）is the most suitable multiple-impeller for the resting cell transformation of canrenone,and it has obtained the highest conversion ratio,which is 47.44%.And good conversion efficiency requires a certain amount of mycelium.（3）Based on the cold model experiment,it can be seen that in the shear thinning fluid,with the increase of rotational speed and ventilation,the three types of multiple-impeller（RT+RT,RT+ABT,RT+CD6）show the trend of increasing gas holdup,shortening mixing time and increasing K_La value.In general,RT+CD6 shows higher gas holdup,mixing characteristics and mass transfer performance.（4）Based on computational fluid dynamics,the numerical simulation results of water-air two-phase flow show that RT+CD6 impeller has faster axial fluid velocity,higher shear strain rate and better gas distribution than six-blade Rushton turbine（lower）and six-blade Rushton turbine（upper）（RT+RT）.Combined with the results of resting cell transformation experiments,it can be inferred that the maximum and average shear strain rates that Aspergillus ochraceus resting cells can tolerate are 2598 s^-1and 52.14 s^-1,respectively.In the two-phase flow of shear-thinning fluid carboxymethyl cellulose aqueous solution-air,RT+RT show the flow field characteristics of fast fluid velocity and average shear rate.The gas distribution of RT+CD6 is homogeneous and the axial velocity of tank wall is higher.The average axial circulation flow rate of six-blade Rushton turbine（lower）and six-arrow blade turbine（upper）（RT+ABT）is higher.In the two-phase flow of xanthan gum aqueous solution-air,the Q_zaveof RT+ABT is higher and the gas distribution is more uniform.It can conclud that the RT+ABT is suitable for the system with large consistency coefficient and small rheological characteristic index.In summary,the RT+CD6 is most suitable for resting cell transformationof canrenone.This study provides a certain reference value for the conversion of canrenone in industrial production.