Integrated downstream processing with membranes

Bioprocesses have several disadvantages over chemical processes: for example, they take place under normal conditions and in highly dilute aqueous solutions; in addition, most products inhibit the productivity of biocatalysts already when present in small concentrations. Therefore a continuous process mode and integration of product recovery are the indispensable prerequisites for an economical production on an industrial scale. Being a demanding procedure which requires 60 to 90 per cent of product cost, depending on the product, downstream processing requires special attention. Bioprocesses are ideally suitable for producing mostly low-molecular weight substances - such as propionic acid, gluconic acid, sorbitol, mannitol, vitamine C substrates, especially from waste waters. The optimization of downstream processing, however, is of central importance in such processes. From the multitude of possible unit operations for downstream processing a few typical examples of special interest are presented. For example; membranes and membrane processes like microfiltration, ultrafiltration, reverse osmosis, pervaporation, electrodialysis also combined with other processes such as flotation extraction, distillation, adsorption, chromatography etc. may be utilized in various ways. (IGB