Extracellular refers to enzymes secreted by a cell, into the surroundings. So, proteases are secreted by cells into a solution, and are downstream processed for retrieval and use. They are used in biological washing powders as an aid to dirt removal [8] as they help to break down protein stains from blood food and grass [7]. Lipases and amylases are also used, to remove starchy food deposits, and cellulose is also added to brighten fabric colours [9]. Disadvantages of using this enzyme, as well as other extracellular enzymes, is that they can contaminate the end product during processing or use, which can affect washing powders effectiveness, and are more expensive to use, as they cannot be re-used, and so must be fermented [7], and processed very often. Also, some people are allergic to proteases due to enzymes on the skin, such as collagen, that can be irritated when in contact, so precaution must be taken when hiring staff and adding an allergy and adequately rinsing before wear, to reduce effects. However, proteases work at lower temperatures; lowering energy costs, whilst producing a suitable turn-over rate, making it a suitable enzyme for use in washing powders. Also, by adding an enzyme, the use of bleaching agents and phosphates are reduced, thus being more environmentally friendly [9].
A biosensor is a sensory system used to analyse biologically active compounds in solutions. Used as a diagnostic tool, biosensors are used in a variety of fields from forensic science to medicine. The main use of biosensors in medical terms is to enable diabetics to monitor their own blood glucose levels or surgeons to monitor during surgery. Glucose is measured with the use of the enzyme glucose oxidase, an immobilised enzyme, that catalyses the reaction between glucose and oxygen in a solution, to form gluconic acid and hydrogen peroxide. The enzyme is connected to an electrode that measures the change in oxygen concentration as blood glucose levels change [5]. Biosensors can also be used to measure the amount of urea in blood or urine, through entrapping urease and attaching it to the tip of a probe. Advantages include ease of and continuous use (immobilised enzymes can be used over again), speed of response, sensitivity in a narrow range, due to specificity from enzymes, and usefulness in a wide range of fields, lowering workloads for police, doctors etc. by serving well in emergency situations/field [10]. However, there are some limitations such as heat sterilisation is impossible as the enzyme would denature, reduction in activity if exposure to extreme pH/temperature occurs, which could eventually impair it, and bacterium could diffuse through membranes, intoxicating cells [2].
Cellulases and esterases are found in fungi, and can break down cellulose into polysaccharides or glucose, to break down and remove “glues, adhesives and coatings that are introduced to pulp during recycling of paper” [12]. The use of esterase improves the removal of glues in pulps, as they are held by ester bonds. Esterase cuts the glues into small, soluble compounds, assisting in their removal from pulp. As these flexible organic materials can affect the quality of paper, and block machinery which can increase hours and cost, this removal is important. However, drawbacks include only working effectively at moderate temperatures and pH, so conditions must be very specific, the introduction of other chemicals in the pulp can act as inhibitors, and as enzymes are specific, some esterases will only be effective on certain types of ester bonds, so variations may be needed [12]. Cellulases are used for de-inking, and are widely used in other industries such as the drying of coffee beans through hydrolysis, and fermentation of biomass into biofuels.
Enzymes, immobilized, intracellular or extracellular, have numerous applications in industry today, to satisfy the world-wide demand for confectionary sweets, detergents, beer, cheese, bread, biscuits and many other products. Since the development of enzyme technology is fairly recent, there is also high commercial value for finding a suitable enzyme and selling it to the major industries in the world. Growing on a large scale and purifying, enzymes are worth the hardship as they can catalayse specific reactions at low temperatures, are more versatile and cheaper than inorganic catalysts [5], reduce workloads in various industries and in some cases, can be used over and over again, having high ecological value.
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Bibliography
1. Page 2
Biological Sciences Review, Volume 19, No.1, September 2006
Dr. Diane Gull
2. Chapter 8
AQA (A) Biology, 2006
Steve Potter
3.
4.
5. Chapter 7
A New Introduction to Biology, 2001
Bill Indge, Martin Rowland, Margaret Baker
6.
7. http://www.biologymad.com/resources/Bioprocessing.pdf
8. Introduction to Biodeterioration
books.google.com
Dennis Allsopp, Kenneth J. Seal, Christine C. Gaylarde
9.
10.
Resources Library
Public Library
11. Enzymes from fungi
Biological Sciences Review, January 2001
Dr. Geoff Robson, Dr. Marilyn Wiebe
12. http://biotech.about.com/od/whatisbiotechnology/a/EverydayEnzymes.htm
