Enzymes are biocatalysts produced by living cells to bring about specific biochemical reactions generally forming parts of the metabolic processes of the cells. Enzymes are highly specific in their action on substrates and often many different enzymes are required to bring about, by concerted action, the sequence of metabolic reactions performed by the living cell. All enzymes which have been purified are protein in nature, and may or may not possess a nonprotein prosthetic group. The practical application and industrial use of enzymes to accomplish certain reactions apart from the cell dates back many centuries and was practiced long before the nature or function of enzymes was understood. Use of barley malt for starch conversion in brewing, and of dung for bating of hides in leather making, are examples of ancient use of enzymes. It was not until nearly the turn of this century that the causative agents or enzymes responsible for bringing about such biochemical reactions became known. Then crude preparations from certain animal tissues such as pancreas and stomach mucosa, or from plant tissues such as malt and papaya fruit, were prepared which found technical applications in the textile, leather, brewing, and other industries. Once the favorable results of employing such enzyme preparations were established, a search began for better, less expensive, and more readily available sources of such enzymes. It was found that certain microorganisms produce enzymes similar in action to the amylases of malt and pancreas, or to the proteases of the pancreas and papaya fruit. This led to the development of processes for producing such microbial enzymes on a commercial scale. Dr. Jokichi Takamine (1894, 1914) was the first person to realize the technical possibility of cultivated enzymes and to introduce them to industry. He was mainly concerned with fungal enzymes, whereas Boidin and Effront (1917) in France pioneered in the production of bacterial enzymes about 20 years later. Technological progress in this field during the last decades has been so great that, for many uses, micro-' Presented at Symposium, Society for Industrial Microbiology, Storrs, Connecticut, August, 1956. bial cultivated enzymes have replaced the animal or plant enzymes. For example, in textile desizing, bacterial amylase has largely replaced malt or pancreatin. At present, only a relatively small number of microbial enzymes have found commercial application, but the number is increasing, and the field will undoubtedly be much expanded in the future. PRODUCTION OF MICROBIAL ENZYMES Enzymes occur in every living cell, hence in all microorganisms. Each single strain of organism produces a large number of enzymes, hydrolyzing, oxidizing or reducing, and metabolic in nature. But the absolute and relative amounts of the various individual enzymes produced vary markedly between species and even between strains of the same species. Hence, it is customary to select strains for the commercial production of specific enzymes which have the capacity for produci...
