However, using enzymes in industry also has disadvantages. Enzymes are very sensitive to environmental changes and need controlled temperatures. They are expensive to purify and are often unstable in their purified state.
An important application of immobilised enzymes is in the food and drink industry. This is as they do not contaminate the product and are used by the enzymes being attached to insoluble substances such as alginates, which usually form membranes and the enzymes bind to the outside of it. This would allow the substrate to pass through the alginate and bind to the enzyme. The immobilised enzyme for example lactose would be easier to recover from the remaining membrane e.g. milk. The advantage of using this process is that it can be reused and it can be continuous.
Bread making is one of the most common food processing techniques. Water, salt and yeast are added to wheat flour to make bread. The wheat flour has naturally occurring enzymes that modify the starch, protein and fibre of the flour when water is added to make dough. The yeast also contains enzymes, which ferment maltose and other sugars during the process to produce carbon dioxide that makes the bread rise. Enzymes are used to produce consistent products and make the process more efficient. The enzymes such as protease are added to the dry flour and activated when water is added to make dough. These help handling the dough and control characteristics such as taste and texture. Baking enzymes means they have to be denatured to inactive proteins during the process. Lipases are now becoming more available for bread making. (www.enzymes.co.uk)
Brewing involves the production of alcohol by the action of yeasts on plant material such as barley. The yeast cells can convert the simple sugars into alcohol and carbon dioxide. Endogenous enzymes are released during malting, which degrades the starch and proteins into simple sugars and amino acids which can be utilised by the yeast cells. Malting is an expensive way to manufacture enzymes and not easy to control. Industrial enzymes such as amylase and proteases can be added to unmalted barley, resulting in same simple sugars and amino acids in a more controlled manner.
Enzymes have been used in the detergent industries since the 1960’s. It is one of the best applications of industrial enzymes in laundry products and washing powders. The main enzyme activity in biological laundry detergents is protease. This acts on organic stains like grass and blood. However, in recent years a mixture of enzyme activity including lipases and amylases. Lipases are effective on stains resulting from fatty products such as oils and lipsticks, whereas amylases remove starchy food deposits. More recently, colour enhancing and anti-bobbling washing powders have been developed containing cellulases. Cellulases remove detached cellulose fibrils that cause dulling of colour as dirt is trapped on the rough surface of the fabric. New products are becoming environmentally friendly as they contain less bleaching agents and phosphates.
Enzymes have also been useful in diagnosing medical conditions. A Clinistix are strips of cellulose which have the enzyme glucose oxidase stuck to one end. When dipped in urine containing glucose, the reaction produces hydrogen peroxide. This reacts with another compound to give a colour change. The colour change would show the patient is potentially diabetic. Minimum quantities of protein in fluids such as blood plasma, can be detected by ELISA (Enzyme-linked immunosorbent assay). ELISA’s can diagnose diseases, as specific proteins are detected in blood plasma. This technique has many applications including the detection of pregnancy and viruses. If a certain protein is detected, antibodies known to bind to the certain protein are fixed to a plate. If this protein is present it binds to the antibody, whereas all other proteins would wash away. A second type of antibody is linked to an enzyme is added and binds to the particular protein at a different site to the first antibody. A specific substrate is then added which binds to the active site of the enzyme. The product formed would be detectable e.g. fluorescent, which allows for a diagnosis to be recognised. (Letts Revise As Biology)
The main applications of enzymes in the leather industry are proteases which help in the dehairing of the animal hides and lipases are used for degreasing. In modern textiles, enzymes are commonly used in the finishing of fabrics and clothes. The main component of cotton and other natural fibres is cellulose. The correct application of cellulase enzyme can remove rough particles giving a glossier fabric. This process is known as biopolishing. The finishing of denim jeans is also a popular application for cellulase in textiles. Before, stonewash denim was faded using pumice stones. Cellulase can replace the stones, causing less damage to the denim. The technique is known as biostoning. Stonewashing enzymes are available as acid cellulases and neutral cellulases.
Enzymes are fast, easy techniques that help speed up reactions in biotechnological processes. They are better than traditional techniques where there was more waste and harmful pollution and by-products produced. The main advantage of using enzymes is that they can be reused, which makes them fairly cheap. Enzymes have helped develop the textiles, medical, food and drink industries.
References:
Letts Revise As Biology: John Parker (pages 52 and 53)
A New Introduction To Biology: Indge, Rowland, Baker.
