Mixing in the mechanically agitated bioreactor: ‘A matter of being stirred, not shaken’

Abstract

Variations in the system parameters can in fact give rise to significant differences in mixing requirement, and failure to operate at the right conditions can result in undesirable outcomes. Biological systems are sensitive to bioreactor hydrodynamics since it directly affects transport processes at the molecular level. In addition, extracellular products and filamentous microbes contribute to drastic changes in the broth characteristics over the course of fermentation, that would in turn alter the mixing needs. Poor mixing or over mixing can both have adverse effects on product quality, but inefficient equipment design leading to excessive energy requirement often goes unnoticed if there are no apparent effects on the product. This paper summarizes the basic considerations to be made for given mixing duties so as to enable operations in a calculated rather than random manner.