The production of industrial enzymes

Abstract

This paper reviews the essential features and current techniques used on an industrial scale in the preparation of partly purified or ‘bulk’ enzymes, as opposed to highly purified enzymes for analytical or diagnostic use, which are covered elsewhere in this volume. Industrial enzymes may be derived from a wide variety of plant, animal or microbial sources, although most production processes rely on the last of these. Microbial enzymes are either extracellular, such as the proteases and carbohydrates, which account for a large proportion of total sales, or intracellular, such as glucose oxidase. Intracellular enzymes usually remain associated with the cell and therefore have to be released, unless the microorganism itself is used as the catalyst. Although specific fermentation procedures adopted by manufacturers vary to a degree, there remain only two principal methods of cultivation, i.e. solid-state and submerged fermentation. Most microbial enzymes are produced by aerobic submerged fermentation, which allows greater control of growth factors than solid-state methods. The recovery and purification techniques discussed are typical of those used for fermentation enzymes, although they may be applied, generally, to most extraction and refining operations irrespective of whether the enzyme source is of plant, animal or microbial origin. In particular the following processes are covered; cell disruption, precipitation and solid-liquid separation including concentration by ultrafiltration. It is shown how, by using a combination of these techniques at different stages in the recovery process, it is possible to produce a complete range of product specifications.