A concentric airlift reactor and stirred tank reactors have been compared for use with immobilized enzyme. Mixing efficiency, specific power input, shear stress, and enzyme stability were compared and discussed. Immobilized penicillin acylase was used as an example for this study. The airlift reactor was found to be superior to the stirred tank reactors in enzyme stability and specific power requirement. Because of lower shear stress and less broken fine enzyme fragments, using an airlift reactor may also be advantageous for downstream product separation.