250 m3. Product isolation was previously based on large-volume extraction of the medium containing the product. Modern isolation and membrane technologies, like reverse osmosis, ultra- and nano-filtration, or affinity chromatography can help to remove salts and by-products, and to concentrate the solution efficiently and in an environmentally friendly manner under mild conditions. The final purification is often achieved by conventional chemical crystallization processes. In contrast to the isolation of small molecules, the isolation and purification of microbial proteins is tedious and often involves a number of expensive large-scale chromatographic operations. Examples of large-volume LMW products made by modern industrial microbial biosynthetic processes are monosodium glutamate (MSG), vitamin B2 (riboflavin), and vitamin C (ascorbic acid). In vitamin B2, riboflavin, the original six- to eight-step synthetic process starting from barbituric acid has been substituted completely by a microbial one-step process, allowing a 95% waste reduction and an approximately 50% manufacturing cost reduction. In ascorbic acid, the five-step process (yield ≈ 85%) starting from D-glucose, originally invented by Tadeus Reichstein in 1933, is being gradually substituted by a more straightforward fermentative process with 2-ketogluconic acid as pivotal intermediate. After the discovery of penicillin in 1928 by Sir Alexander Fleming from colonies of the bacterium Staphylococcus aureus, it took more than a decade before a powdery form of the medicine was developed. Since then, many more antibiotics and other secondary metabolites have been isolated and manufactured by microbial fermentation on a large scale. Some important antibiotics besides penicillin are cephalosporins, azithromycin, bacitracin, gentamicin, rifamycin, streptomycin, tetracycline, and vancomycin. Cell Cultures Animal or plant cells, removed from tissues, will continue to grow if cultivated under the appropriate nutrients and conditions. When carried out outside the natural habitat, the process is called cell culture. Mammalian cell culture fermentation, also known as recombinant DNA technology, is used mainly for the production of complex big molecule therapeutic proteins, a.k.a. biopharmaceuticals. The first products made were interferon (discovered in 1957), insulin, and somatropin. Commonly used cell lines are Chinese hamster ovary (CHO) cells or plant cell cultures. The production volumes are very small. They exceed 100 kg per year for only three products: Rituxan (Roche-Genentech), Enbrel (Amgen and Merck & Co. [formerly Wyeth]), and Remicade (Johnson & Johnson). Fine chemical production by mammalian cell culture is a much more demanding operation than conventional biocatalysis and –synthesis. The bioreactor batch requires more stringent controls of operating parameters, since mammalian cells