Some Fundamental Innovations in Direct Solvent Extraction of Low Molecular Weight Biological Products

Abstract

The separation of low molecular weight biologically produced molecules by fermentation processes is a very important area of development in the pharmaceutical industry and elsewhere. The problems of separation processes for economic exploitation are significant. The use of liquid-liquid solvent extraction as a means of recovering such products is chemically very attractive on account of the high degree of selectivity control which is available by adjustment of both the chemical and physical structure of the solvents. The paper reviews some of the problems arising from using solvent extraction especially in relation to mass transfer processes, physical contacting processes, and product and solvent recovery. The technical and scientific issues surrounding rheology and the presence of surfactants and solid material in the extraction of fermentation solutions are discussed in some detail. The influence of such phenomena on droplet behaviour is a particular source of focus in the paper. The use of novel contacting techniques including intensified electrostatic contact for both dispersion and coalescence purposes is described. The application of these techniques to some well known biological product extractions are reviewed briefly including those for ethanol and penicillin G. The potential application of solvent extraction to some of the more recent biological products including arene cisdihydrodiols is reviewed briefly. Some of the implications for equipment application and, design are also reviewed in relation to direct extraction of biological products.

Keywords:

• Extraction
• bioseparation
• downstream processing