Integrating biochemical separation and purification steps in fermentation processes.

Owing to recent developments in molecular biology and biotechnology, we have seen rapid growth in the development of industrial processes to produce valuable substances by microbial means. The idea is not new to the fermentation technologist because they are the means for producing beverages, antibiotics, and many other complex organic materials for commercial use. There are some inherent engineering disadvantages of fermentation processes as compared to conventional chemical processes that need to be solved in order to make these processes economically attractive. The traditional fermentation process involves growing a pure culture of a microorganism that produces the product of interest in a fermenter after sterilization and inoculation. The fermentation can be carried out in batch, semicontinuous, and continuous modes. Depending on whether the desired product is intracellular or extracellular, the harvested broth is then subjected to various separation and purification steps until the specific product of interest is isolated from the fermentation broth. The common steps involved are cell removal, volume reduction, isolation, and purification until the specified product purity has been achieved.' The fermentation and the subsequent recovery steps have traditionally been carried out in separate departments and interaction among these groups has been minimal. Kaufman and Paul2 pointed out the interactive nature of these steps, especially between the fermentation and its subsequent product recovery scheme. In this paper, this interactive nature can be examined and utilized to optimize the entire biochemical process. A hybrid extractive fermentation system developed at the University of Michigan will be used as a model system to illustrate this point.