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, azythromycin, bacitracin, gentamycin, 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 are heat and shear sensitive; in addition the growth rate of mammalian cells is very slow, lasting from days to several months. While there are substantial differences between microbial and mammalian technologies (e.g., the volume / value relationships are 10 $/kg and 100 tons for microbial, 1,000,000 $/kg and 10 kilograms for mammalian technology; the cycle times are 2–4 and 10–20 days, respectively), they are even more pronounced between mammalian and synthetic chemical technology (see Table 1). The mammalian cell production process, as used for most biopharmaceuticals, is divided into the four main steps: (1) Cultivation, i.e. reproduction of the cells; (2) Fermentation, i.e. the actual production of the protein, typically in 10,000 Liter, or multiples, bioreactors; (3) Purification, i.e. separation of the cells from the culture medium and purification, mostly by chromatography, (4) Formulation, i.e. conversion of the sensitive proteins to a stable form.