Immobilized Cell Bioreactors

Immobilization of viable microbial cells, which can be achieved by attachment, aggregation, entrapment, or confinement, localizes the cells into a defined region and allows for the repeated use of their catalytic activity. The ability to design and manufacture immobilized cell particles in many shapes and sizes with the desired density also makes it possible to use these particles as a discrete phase in the bioreactor, and to decouple their hydrodynamic behavior from that of the other existing phases. As a result of these characteristics a whole host of bioreactor configurations including stirred tank, fixed-bed, fluidized-bed, gas-agitated, and membrane bioreactors can be used with immobilized cells and the user could take advantage of other flexibilities such as operation of the bioreactor at short residence times and high loading rates. Prolonged stability, enhanced biomass hold-up, reaction selectivity, increased product yield, and simplification of the downstream processing are other advantageous characteristics of the immobilized cell bioreactors. Research on the basic and applied aspects of cell immobilization has led to the development of many practical applications in the field of environmental bioengineering, production of foods, beverages, pharmaceuticals, and biochemicals, and most importantly biomedical engineering and medicine. This article aims to provide a brief overview of the primary topics as related to cell immobilization and immobilized cell bioreactors.