Isolation of Microbial Natural Products

Microbial fermentations conducted with the express purpose to generate organic molecules are invariably carried out in a liquid medium, and the organic components produced can be distributed between both the solid and liquid phases. A major challenge facing the practitioner attempting to isolate a microbial natural product, where the organic component is extracellular and has been exuded into the medium, is the separation of the desired organic components from the aqueous broth that constitutes the majority of the mass. This chapter places natural products in a medicinal context from a historical perspective, demonstrating that biological activity in natural compounds has a long history. It subsequently goes on to summarize, using appropriate examples, two methods invaluable in the isolation of microbial natural products. The techniques considered are liquid-liquid extraction concentrating on countercurrent methods of separation and liquid-solid extraction focusing on the use of polymeric adsorbents in separation.