(atorvastatin), where the pivotal intermediate R-3-Hydroxy-4-cyanobutyrate is now made with a nitrilase, and Merck & Co.'s Singulair (montelukast), where the reduction of a ketone to S-alcohol, which had required stoichiometric amounts of expensive and moisture sensitive "(-)-DIP chloride" is now replaced by a ketoreductase enzyme catalyst step. Similar rewarding switches from chemical steps to enzymatic ones have also been achieved in steroid synthesis. Thus, it has been possible to reduce the number of steps required for the synthesis of Dexamethasone from bile from 28 to 15. Enzymes differ from chemical catalysts particularly with regard to stereoselectivity, regioselectivity, and chemoselectivity. They can also be modified ("reshuffled") for specific reactions, for use in chemical synthesis. "Immobilized enzymes" are those fixed on solid supports. They can be recovered by filtration after completion of the reaction. Conventional plant equipment can be used with no, or only modest, adaptations. The International Union of Biochemistry and Molecular Biology (IUBMB) has developed a classification for enzymes. The main categories are Oxidoreductases, Transferases, Hydrolases, Lipases (subcategory), Lyases, Isomerases and Ligases, Companies specializing in making enzymes are Novozymes, Danisco (Genencor). Codexis is the leader in modifying enzymes to specific chemical reactions. The highest-volume chemicals made by biocatalysis are bio-ethanol (70 million metric tons), high-fructose corn syrup (2 million metric tons); acrylamide, 6-aminopenicillanic acid (APA), L-lysine and other amino acids, citric acid and niacinamide (all more than 10,000 metric tons). Biosynthesis i.e. the conversion of organic materials into fine chemicals by microorganisms, is used for the production of both small molecules (using enzymes in whole cell systems) and less complex, non-glycosylated big molecules, including peptides and simpler proteins. The technology has been used for 10,000 years to produce food products, like alcoholic beverages, cheese, yogurt, and vinegar. In contrast to biocatalysis, a biosynthetic process does not depend on chemicals as starting materials, but only on cheap natural feedstock, such as glucose, to serve as nutrient for the cells. The enzyme systems triggered in the particular microorganism strain lead to the excretion of the desired product into the medium, or, in the case of HMW peptides and proteins, to the accumulation within so-called inclusion bodies in the cells. The key elements of fermentation development are strain selection and optimization, as well as media and process development. Dedicated plants are used for large-scale industrial production. As the volume productivity is low, the bioreactors, called fermenters, are large, with volumes that can exceed