Enzymes used industrially are obtained from microbial sources such as fungi and bacteria for several reasons, firstly in comparison to their size they produce a lot of enzyme molecules, they are also easy to manipulate genetically. They are able to grow in laboratories anywhere in the world regardless of the world environmental conditions.
Most industrial enzymes are extra cellular enzymes this is when they are secreted by micro organisms.
Fermenters are used to grow micro organisms that produce useful enzymes on a large scale, it is a stainless steel ‘tank’ in which the micro organisms are placed in with nutrients to enable them to reproduce. The nutrients are often carbon, nitrogen sulphur and oxygen as well as extra growth factors such as amino acids and vitamins. Conditions such as pH temperature and oxygen are monitored using probes. The two methods of fermentation are batch and fed batch fermentation, batch fermentation is when the nutrient and micro organisms are kept in the fermenter till all the nutrients are used up nothing but waste gasses are removed during this process. Fed batch however requires environmental factors to constantly change, except the temperature.
The culture media must contain a balanced mixture of nutrients and carbon, nitrogen and oxygen source. If in excess it can inhibit the growth of the micro organisms. Growth factors and buffers are often added.
The culture medium is heated to avoid contamination, also to maintain aseptic conditions the equipment is cleaned with hot water and sterilised with steam, the air supply is sterilised by filtration and the interior surfaces of the fermenter are polished to avoid trapping micro organisms.
The extraction and purification of the end product is called down streaming. It involves processing, filtration to separate cells from solution, centrifugation of the cells and finally drying and packaging.
To allow quick and easy removal of enzymes from end products immobilised enzymes are used, these are enzymes bound to a surface e.g. an insoluble matrix such as collagen, this matrix allows the enzymes to be held together in one place and so can be removed and reused.
Enzymes in industries
1. The textile industry
Enzymes were first used by the textile industry to remove starch paste from fabrics, starch was applied to thread to protect it during weaving. Amylase catalyses the hydrolysis of the starch, it breaks the alpha 1-4 links between the glucose molecules that make up the starch, this forms maltose and a few glucose molecules still bonded together. The process is known as desizing and doesn’t harm the fabric.
Hydrogen peroxide is often used as a bleach before dyeing fabrics such as cotton, it is necessary that this is removed, to do this the enzyme catalyse is added this breaks down the hydrogen peroxide into water and oxygen, this waste is clean and environmentally desirable.
Enzymes have also replaced stones in ‘stone-washing’ this is a designing method used, it has also replaced bleaches, this has resulted in major reduction in power usage as enzymes work at moderate temperatures and do not need to be heated very much. Enzymes have replaced the use of volcanic lava stones in the preparation of Denim these stones damaged both the fabric and the machinery used.
2. Alcohol fermentation
This process has been carried out since ancient times, often unknowing. Fermentation is used to make all alcoholic drinks however some drinks are distilled after fermentation to increase the alcohol content.
The enzymes in the fungus yeast catalyse the hydrolysis of glucose to ethanol (alcohol) and carbon dioxide.
3. The paper industry
For pulps (wood fibres) to be made suitable for the production of paper they must go through a chemical process that uses chlorine as a bleach, this produces chlorinated compounds as waste products. By using the enzyme Xylanases less chlorine can be used during bleaching. Enzymes are also used to remove fine particles from the pulp.
Before recycling paper it is essential that it is de-inked, this can be done using enzymes such as novovym 342 and placing them in water with the paper, the ink particles float to the surface and are removed.
Pitch is a sticky substance present mainly in pulps. Pitch causes problems in paper machines and can be removed by lipases.
4. Tannery
The enzyme protease is used to remove the hair from animal hides. They digest away the protein content of the cells that hold the hair follicles in place, so the hair simply drops out.
The removal of grease from the hide can be carried out using lipase. The use of lipases is a fairly new development in leather industry.
Lipolytic enzymes improve water uptake by the dry skins, removal and degradation of protein and reduces the processing time.
Enzymes are also used to assist the alkaline chemical process. This results in a more environmentally friendly process and improves the quality of the leather.
Finally the protein is partly degraded by the enzyme trypsin to make the leather soft and easier to dye.
5. Medicine
Proteases are also used to extract heparin, which is used to prevent blood clotting during surgery. This is extracted from the intestines of pigs , the lining is scrapped off proteases are added and from the protein breakdown heparin is harvested.
Enzymes are vitally important in preventing excessive blood clotting and reducing the "stickiness" of the platelets and red blood cells.
Trypsin and chymotrypsin are used in fibrinolysis, a process that dissolves blood clots. Enzymes help remove metabolic waste and generally improve circulation.
Thrombosis is what happens when there are blot clots in damaged blood vessels, these clots can be dislodged and carried around and may block a smaller artery causing a heart attack. As blood clots are a net of fibrin (insoluble proteins in which blood cells are trapped), and they can be digested by enzymes such as trypsin and protease as they are proteins and are converted into amino acids, freeing the trapped blood cells and getting rid of the clot. This process is called fibrinolysis.
Enzymes can be used to detect and measure amounts of glucose. The amount of glucose in the blood and urine is a crucial indicator in the diagnosis of Diabetes mellitus, this is when there is a deficiency of insulin resulting in high glucose levels in the blood. It is detected using the enzyme “glucose oxidase” and a biosensor. This instrument uses glucose oxidase as its biological system. The enzyme catalyses the reaction between glucose and oxygen to form gluconic acid. The biosensor then uses the amount of gluconic acid produced to indicate the quantity of glucose and oxygen there was in the blood.
Viruses are cell parasites consisting of nucleic acids covered by a protein film. The protein cover of the viruses can be dissolved or at least inactivated by proteolytic enzyme activity which leads to a loss of viral infectivity.
