ABSTRACT
The central problem in the extraction of fermentation products from the fermentation broth (‘beer’) is that the required product usually (but not always) forms a small proportion of a complex heterogeneous mixture of cell debris, other metabolic product, and unused portions of the medium. Thus, product recovery equipment and processes are as important as the fermentor in a fermentation industry; and may be expensive. Factors such as the value of the final product, the degree of purity required to make the final product acceptable, bearing in mind its revenue-yielding potential, the chemical and physical properties of the product, the location of the product in the mixture, i.e. whether it is free within the medium or is cell-bound, and the cost-effectiveness or the economic attractiveness of the available alternate isolation procedures, are to be considered in deciding on the best extraction method. The product sought could be the cells themselves, such as in yeast manufacture, lodged in the cells (such as in streptomycin or some enzymes), or free in the medium as with penicillin. This chapter discusses processes for product isolation such as filtration, centrifugation, coagulation, flocculation, foam fractionation, whole broth treatment, cell disruption, liquid extraction, dissociation extraction, ion-exchange adsorption, precipitation, carbon decolorization, crystallization, and drying.
