AIRLIFT REACTORS: CHARACTERISTICS, APPLICATIONS AND DESIGN CONSIDERATIONS

Bioreactors of the airlift type are a promising design for aerobic fermentations. The basic knowledge required for understanding and predicting the performance of these reactors is only now beginning to emerge. In this review we present our observations and those of other investigators in an attempt to build up a coherent picture of airlift devices. All the major aspects—mixing and hydrodynamics, mass and heat transfer—in these reactors are considered. Comparisons between bubble columns and airlift systems are made where analogies, similarities and/or differences between them provide insight into airlift systems. Throughout, the areas of particular concern and those in need of further research in this field are mentioned. Extensive work on all forms of airlift reactors, particularly in non-Newtonian media—homogeneous and suspensions—remains to be done. Current knowledge does not permit airlift reactor design with a high degree of confidence. However, the technical feasibility of all types of fermentations—plant cell, tissue culture, bacterial, fungal, and those utilizing yeasts—in airlift vessels has been demonstrated.