The engineering effects of fluids flow on freely suspended biological macro-materials and macromolecules.

The manufacture of many biotechnologically important products requires consideration of the physical breakage and biochemical degradation pathways at all stages during processing, storage and transportation. The engineering flow environment in most items of bioprocess equipment has long been recognised as a key factor in determining these pathways and is the focus of the present review. Because of its industrial significance, the detrimental effects of the engineering flow environment on freely suspended bioparticles have been the subject of many scientific investigations over the past few decades. There is a general consensus of opinion that fluid shear and elongational stresses are the two main breakage pathways of relevance to processing of most biomaterials. An additional degradation pathway has also been identified involving significant losses of biological activity of macromolecules at gas-liquid, gas-solid and liquid-liquid interfaces. In such cases, the engineering flow field is shown to have a secondary role in determining the kinetics of inactivation. An equally important consideration in the optimisation of the relevant unit operations is the biomechanical integrity of the flow sensitive material. The biomechanical and biorheological parameters that determine the integrity of biomaterials are poorly defined, their evaluations present future research challenges and are of immediate engineering significance.