The large-scale use of enzymes in solution

Many of the more important industrially useful enzymes have been referred to earlier (see Table 2.1). The value of the world enzyme market has rapidly increased recently from £110M in 1960, £200M in 1970, £270M in 1980, £500M in 1985 to an estimated £1000M for 1990, representing an increase from 10% of the total catalyst market in 1980 to almost 20% in the 1990s. This increase has reflected the rise in the number of enzymes available on an industrial scale at relatively decreasing cost and the increasing wealth of knowledge concerning enzymes and their potential applications. As enzyme costs generally represent a small percentage at most, of the cost of the final product, it can be deduced that enzymes are currently involved in industrial processes with annual turnovers totalling many billions of pounds. Several enzymes, especially those used in starch processing, high-fructose syrup manufacture, textile desizing and detergent formulation, are now traded as commodity products on the world's markets. Although the cost of enzymes for use at the research scale is often very high, where there is a clear large-scale need for an enzyme its relative cost reduces dramatically with increased production.

Relatively few enzymes, notably those in detergents, meat tenderisers and garden composting agents, are sold directly to the public. Most are used by industry to produce improved or novel products, to bypass long and involved chemical synthetic pathways or for use in the separation and purification of isomeric mixtures. Many of the most useful, but least-understood, uses of free enzymes are in the food industry. Here they are used, together with endogenous enzymes, to produce or process foodstuffs, which are only rarely substantially refined. Their action, however apparently straightforward, is complicated due to the effect that small amounts of by-products or associated reaction products have on such subjective effects as taste, smell, colour and texture.

The use of enzymes in the non-food (chemicals and pharmaceuticals) sector is relatively straightforward. Products are generally separated and purified and, therefore, they are not prone to the subtleties available to food products. Most such enzymic conversions benefit from the use of immobilised enzymes or biphasic systems and will be considered in detail in Chapters 5 and 7.