Bacterial Enzymes
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Bacterial Enzymes WIM J. QUAX
Introduction In the living world, each chemical reaction is catalyzed by its own enzyme. Enzymes exhibit a high specificity, as they are able to discriminate between slightly different substrate molecules. Furthermore, they have the ability to operate at moderate temperature, pressure and pH, which makes them attractive catalysts for industrial and household conversion processes. The first reports on the industrial use of enzyme products go back to the beginning of the last century. It was the German scientist Röhm who introduced the use of bovine pancreas extracts for the removal of stains in dirty clothing (Röhm, 1915; Fig. 1). Around the same time, the Laboratoire Amylo in France experimented with the use of extract from Bacillus for conversion of starch into sugars (Fig. 2). As a result, the company Rapidase (Seclin, France), which is now part of the life science division of DSM, was formed. With the development of microbial fermentations in the second half of the last century, the number of industrial processes performed by enzymes and the amount of enzymes produced have increased sharply. At present, a renewed worldwide research effort has been directed to identifying more sustainable and environmentally friendly biocatalytic processes. The availability of highly specific and cheap enzymes resulting from genetic and protein engineering has been very instrumental in reviving interest in the industrial application of enzymes. Most classically used industrial enzymes are hydrolytic (proteolytic, amylolytic, or lipolytic). Hydrolytic enzymes hardly require any cofactors, which allows their application in a great variety of conditions. These enzymes are usually separated from the cell broth after fermentation and formulated in more or less high concentrations. Recently, more specialized bioconversions have been developed in which enzymatic activity is maintained only by special cofactors that must be regenerated or, even worse, by living cells. In this chapter, the emphasis will be on bacterial enzymes that can be used in isolated form.
The organization of this chapter has focused on application. Owing to the versatility and stability of hydrolytic enzymes, the same enzyme may be used in totally different parts of industrial processes. Table 1 summarizes the current use of enzymes in various industry and household applications. The data are compiled from information provided by enzyme producers, customers, and industry organizations and from information acquired as a result of my involvement with industrial enzyme production for many years. As it relates to products of commercial importance, access to the data is not always possible, and relating the biochemical and genetic characteristics of production strains, which are usually proprietary, to better described strains in the literature is sometimes difficult. Nevertheless, this manuscript should provide an overview of the importance of bacterial enzymes for sustainable and efficient conversion in
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