The application of enzymes in industry and medicine

* Detergents

Enzymes have been used in the detergent industry since the mid 1960's and are probably the best known application of industrial enzymes especially in laundry products - the so-called "biological" washing powders, liquids and tablets.

The main enzyme activity in biological laundry detergents is protease that acts on organic stains such as grass, blood, egg and human sweat. However, it has become more common in recent years to include a "cocktail" of enzyme activities including lipases and amylases. Lipases are effective on stains resulting from fatty products such as oils and fats whilst amylases help remove starchy food deposits.

More recently, colour enhancing and "anti-bobbling" washing powders have been developed which contain cellulases. It is thought that the Point of action of such cellulases is to remove detached cellulose fibrils, which cause a progressive dulling of the colour as dirt is trapped on the rough surface of the fabric.

Enzymes have become particularly important in products developed for the spot application onto laundry. In these cases soils are loosened by enzyme before they are added to the main wash in a detergent. Such products result in reduced detergent costs and the ability to save energy by lower temperature washing.

The use of enzymes in automatic dishwashing detergents is also becoming popular. Typical enzyme activities are protease and amylase to remove food particles. Such new products are more environmentally friendly as they contain less bleaching agents and phosphates.

* Pulp and Paper

The raw material for all types of paper manufacture is wood. The process of pulping involves the separation of useful cellulose fibres from lignin and other components. Pulping can be performed by mechanical and/or chemical processes. Mechanical pulping gives a high yield of pulp but is of poor quality as lignin components are not significantly solid. Such mechanical pulps are mainly used for the manufacture of newsprint.

Other applications of enzymes in pulp and paper manufacture include pich control, modification of starch for coated papers and cellulose fibre modification to produce softer tissue papers.

* Enzymes in Baking

Bread baking is one of the most common food processing techniques throughout the world although the bread products of different countries vary in their finished form. The basic component of all bread is wheat flour to which is added water, salt and yeast. Other ingredients are sometimes added such as sugar, fats and flavouring components. The main components of wheat flour and their relative abundance are 82% starch, 12% protein and 3% fibre.

The wheat flour has naturally occurring enzymes that modify the starch, protein and fibre fraction of the flour when water is added to the flour to make the dough. Similarly the added yeast also have their enzymes and ferment maltose and other sugars during the "proving" stage to produce carbon dioxide that makes the bread rise. Literally therefore the breadmaking process is an ancient form of fermentation by a combination of enzymes from yeast and wheat, followed by baking. This converts wheat from a difficult to digest material to a basic life need.

Wheat is favoured for breadmaking because the protein fraction in wheat flour contains the special proteins glutenin and gliadin which when mixed together form gluten. Gluten is a large network which is very viscous and elastic. It is this network which gives doughs their unique consistency and holds the gas from yeast fermentation during baking to form the open crumb structure of the finished leavened bread. Other cereals such as barley, rye and soya do not have this type of gluten and so form heavier, denser breads. Modification of this gluten protein with proteases can have a dramatic effect on the appearance of the bread. Proteases are also used to weaken gluten to give more plastic dough properties required for making biscuits.

The non-starch polysaccharides in flour also play an important role in bread quality as they are responsible for much of the water absorption in a dough and interact with the gluten complex. The addition of xylanases and other fibre-degrading enzymes have been shown to have a dramatic effect on the dough and finished bread characteristics.

* Pharmaceuticals and Diagnostics

Enzymes have many roles in the pharmaceutical and diagnostic industries. There are too many applications to cover but typical applications include:

* Enzymes as direct pharmaceutical products such as in the treatment of genetic disorders leading to a specific enzyme deficiency.

* Extraction of medicinally important compounds such as heparin.

* Manufacture of chemical pharmaceuticals where enzymes are used for the interconversion of chemical intermediates or the removal of chiral components.

* Combinatorial biocatalysis.

* Research and development - especially in the field of molecular biology where almost all the processes of nucleic acid manipulation are performed with enzymes (eg. restriction endonucleases and DNA polymerases).

* Diagnostic procedures also frequently utilise enzymes - some examples include luciferase, glucose oxidase.

* Brewing

Beer brewing essentially involves the the production of alcohol by the action of yeasts on plant materials such as barley, maize, sorghum, hops and rice. The yeast cells are capable of converting simple sugars into alcohol and carbon dioxide. However, most of the sugar present in plant materials is in the form of complex polysaccharides such as starch and cannot be readily utilised. Traditionally these nutrients are "released" by the process of malting whereby barley is allowed to partly germinate during which endogenous enzymes are released which degrade starch and protein to simple sugars and amino acids which can be utilised by the yeast cells.

The malting process is a relatively expensive way of manufacturing enzymes and is not always easy to control. Industrial enzymes such as amylases, glucanases and proteases can be added to unmalted barley resulting in the same simple sugars and amino acids that malting would liberate but in a more controlled fashion.

Enzymes also play an important role as filtration improvers. Slow filtration of the mash or final beer often results from the presence of viscous polysaccharides such as xylans and glucans. Pretreatment with xylanases or glucanases break down these viscous polysaccharides thereby increasing filtration rates and preventing fouling of filtration membranes.

* Fruit Juices

Enzymes are used in the processing of noncitrus fruits to maximise the production of clear juice.

Nearly all fruits and berries contain pectins and other polysaccharides such as starch and aribinoxylans. Pectins hold the fruit cells together like a "glue" and result in poor liberation of juice during pulping. The presence of soluble pectins in the subsequent juice also causes hazing. The addition of pectin degrading enzymes (pectin methyl esterase, polygalacturonase and pectin lyase) at the pulping stage increases the yield of juice and helps in the clarification. Pectin degrading enzymes are particularly important in the production of fruit juice concentrates as pectins can form very viscous gels, which delay filtration and concentration to high levels of dissolved solids.

Cellulases also play a role in the extraction of juice from berries where juice yield together with the extraction of colour and flavour components can be difficult.