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Industrial applications Enzymes are used in the chemical industry and other industrial applications when extremely specific catalysts are required. However, enzymes in general are limited in the number of reactions they have evolved to catalyze and also by their lack of stability in organic solvents and at high temperatures. Consequently, protein engineering is an active area of research and involves attempts to create new enzymes with novel properties, either through rational design or in vitro evolution. Application Enzymes used Uses Fungal alpha-amylase Catalyze breakdown of enzymes are normally starch in the flour to sugar. inactivated at about 50 Yeast action on sugar Baking industry degrees Celsius, but are produces carbon dioxide. destroyed during the baking Used in production of white process. bread, buns, and rolls. alpha-amylase catalyzes the release of sugar monomers from starch Biscuit manufacturers use Proteases them to lower the protein level of flour. Baby foods Trypsin To predigest baby foods. They degrade starch and Enzymes from barley are proteins to produce simple released during the sugar, amino acids and Brewing industry mashing stage of beer peptides that are used by production. yeast for fermentation. Widely used in the brewing Industrially produced barley process to substitute for the enzymes natural enzymes found in barley. Amylase, glucanases, Split polysaccharides and Germinating barley used for malt. proteases proteins in the malt. Betaglucanases and Improve the wort and beer arabinoxylanases filtration characteristics. Amyloglucosidase and Low-calorie beer and pullulanases adjustment of fermentability. Remove cloudiness Proteases produced during storage of beers. Acetolactatedecarboxylase Avoid the formation of (ALDC) diacetyl Fruit juices Cellulases, pectinases Clarify fruit juices Rennin, derived from the stomachs of young ruminant Manufacture of cheese, animals (like calves and used to hydrolyze protein. Dairy industry lambs). Microbially produced Now finding increasing use enzyme in the dairy industry. Is implemented during the production of Roquefort Lipases cheese to enhance the ripening of the blue-mould cheese. Roquefort cheese Break down lactose to Lactases glucose and galactose. Meat tenderizers Papain To soften meat for cooking. Amylases, Converts starch into amyloglucosideases and glucose and various syrups. glucoamylases Starch industry Converts glucose into Glucose Fructose fructose in production of Glucose isomerase high fructose syrups from starchy materials. These syrups have enhanced sweetening properties and lower calorific values than sucrose for the same level of sweetness. Paper industry Degrade starch to lower viscosity, aiding sizing and coating paper. Xylanases reduce bleach required for decolorising; cellulases Amylases, Xylanases, smooth fibers, enhance Cellulases and ligninases water drainage, and promote ink removal; lipases reduce pitch and lignin-degrading enzymes remove lignin to soften A paper mill in South Carolina. paper. Used to break down cellulose into sugars that Cellulases Biofuel industry can be fermented (see cellulosic ethanol). Cellulose in 3D Ligninases Use of lignin waste Used for presoak conditions Primarily proteases, and direct liquid applications produced in an extracellular helping with removal of form from bacteria Biological detergent protein stains from clothes. Detergents for machine dish Amylases washing to remove resistant starch residues. Used to assist in the Lipases removal of fatty and oily stains. Laundry soap Used in biological fabric Cellulases conditioners. To remove proteins on Contact lens cleaners Proteases contact lens to prevent infections. To generate oxygen from Rubber industry Catalase peroxide to convert latex into foam rubber. Dissolve gelatin off scrap Photographic industry Protease (ficin) film, allowing recovery of its silver content. Used to manipulate DNA in genetic engineering, important in pharmacology, Molecular biology agriculture and medicine. Restriction enzymes, DNA Essential for restriction ligase and polymerases digestion and the Part of the DNA double helix. polymerase chain reaction. Molecular biology is also important in forensic science. Enzymes in the environment Enzymes perform a wide range of very important functions throughout nature. They are highly specific and efficient, guiding the biochemistry of life with great precision and fidelity. This fidelity is essential in the cells of living organisms, and a multitude of mechanisms have evolved for controlling the activity of these enzymes themselves. Enzymes play a key role in harvesting energy from the sun via photosynthesis, perform a wide range of metabolic functions throughout every living cell in the bodies of plants and animals, and are in fact really the catalysts of all biological processes constituting life on earth. Bacteria and fungi also contain enzymes that are essential to their survival in the environment. These organisms live in a variety of habitats, some fairly moderate (these organisms are called mesophiles) and others in extreme environments such as hydrothermal vents, hot springs, and sulphataric fields (extremophiles). As extremophiles have adapted to these extreme habitats, they produce enzymes (biocatalysts) that are able to function under conditions that their mesophilic counterparts are not able to tolerate, and therefore are highly exploitable in research areas such as bioremediation and biocatalysis. Detoxifying the environment Biodegradation is the natural degradation of matter in the natural environment in the absence of any human intervention. Bioremediation, in contrast, is characterised by human intervention and is the technology of pollution treatment, using biological systems to transform and convert various pollutant species in the environment to less toxic or non-toxic forms. An effective bioremediation will produce harmless water and carbon dioxide as the end products, which are then able to re-enter natural ecosystems. Tiny microorganisms such as bacteria are often the agents of choice for bioremediation. Scientists at Rhodes University have successfully exploited the sulphate reducing bacteria (SRB) and methanogenic producing bacteria (MPB) for treatment of municipal primary sewage and acid mine drainage (AMD) wastes. Both these bacterial populations dramatically increase the rate of hydrolysis of solid wastes under anaerobic conditions, and are also able to work together in a very effective manner: The high levels of sulphate and metals contained in acid mine drainage are removed using SRB, while the sulphide produced by the SRB dramatically increases the rate at which the MPB hydrolyses primary sludge. Biocatalysis by extremophiles Enzymes produced by extremophiles (bacteria and fungi living in harsh conditions) are also highly exploitable in the biocatalytic industry. For example, thermophiles are organisms that live under conditions of extreme high temperature. These produce thermophilic enzymes that are readily exploited in industry, such as amylase, xylanases used in paper bleaching, proteases used in baking, brewing and in detergents, as well as DNA polymerase enzymes used in genetic engineering. Psychrophilic enzymes are present in psychrophiles, organisms that have adapted to very cold climates, such as those microorganisms living in the Artic and Antarctic regions. The psychrophiles are used in cheese maturation and in the dairy industry (e.g. proteases) and biosensors (e.g. dehydrogenases). Similarly, there are a host of other enzymes that are acidophilic (tolerant to low pH), piezophilic (tolerant to high pressure) and metalophilic (tolerant to high metal concentration). There is even a bacterium, Deinococcus radiodurans, which is the most radiation-resistant organism known and is recently being targeted and engineered for the bioremediation of radioactive waste. The sulphate reducing bacteria mentioned previously belong to the class of acidophiles, as they are able to live in highly acidic environments in acid mine drainage rich environments. Monitoring the environment These enzymes may have another important purpose - they can serve as indicators of the "biochemical health" of the environment. Scientists can selectively target and monitor certain molecules in nature which can help them keep track of environmental pollution biodegradation and bioremediation processes in a particular system such as a polluted river or in a waste recycling plant. This is a relative new field of research, but already key molecules have been identified in nature that may provide a lot of information regarding the "metabolic state" of a system. For example, monitoring enzymes responsible for sulphate activation and reduction in anaerobic bacteria living in marine and estuarine sediments can indicate the level of metabolic activity (sulphate activation and reduction) that is occurring in these sediments. At the Department of Biochemistry, Microbiology and Biotechnology at Rhodes University, we are currently investigating enzymes and other biomolecules which can potentially provide more information regarding the metabolic state of natural systems, thereby monitoring the processes of bioremediation more effectively. Novel metabolic pathways in nature Although metabolic pathways in nature have for the most part been well studied and characterised, there are still many pathways that exist in nature that are poorly understood. At Rhodes, scientists are focusing efforts on the natural biodegradative processes at work in nature that are responsible for the cleavage of complex aromatic compounds. There is still much to learn from enzymes, as they continuously surprise scientists with their remarkable adaptability to extreme conditions. As a result of increasingly more recalcitrant chemical pollutants finding their way into the environment, microorganisms, and the enzymes they possess, have to constantly adapt in order to deal with the presence of the pollutants. Microorganisms either respond by implementing and optimising existing metabolic reaction pathways in their genetic make-up to degrade harsh chemical poolutants, or they develop new pathways, degrading these compounds into non-toxic components or elements that can be reassimilated for their own cellular metabolism and survival. SUGAR SYRUPS FROM STARCH Environmental Benefits: Reduced use of strong acids and bases, reduced energy consumption (less greenhouse gas), less corrosive waste, and safer production environment for workers. DAIRY APPLICATIONS Environmental Benefit: Cheese makers are no longer dependent upon enzymes recovered from slaughtered calves, kids and lambs for production of rennet needed for most cheese making. Based on current demand for chymosin, commercial needs for rennet could not be met from animal sources. CLEAR CLEAR FRUIT JUICE Environmental Benefit: The use of enzymes in juice processing helps assure that the maximum amount of juice is removed from the fruit, thereby reducing waste and controlling costs. MEAT TENDERIZING Environmental benefits: Less waste, better use of raw materials. CONFECTIONS Environmental Benefit: Enzymes replace hydrochloric acid in the manufacturing process, thereby eliminating the need for harsh chemical processing and thereby reducing risk to the environment. Elimination of a strong acid also provides a safer workplace. LOWER TEMPERATURE & NO PHOSPHATE CLOTHES Environmental Benefits: Reduced phosphate load to rivers and lakes. Reduced energy consumption with lower temperature washing. ETHANOL FUEL FROM RENEWABLE Environmental benefit: Greater utilization of natural, renewable resources, safer factory working conditions, reduced harmful auto emissions. LEATHER TANNING DEHAIRING BATING Environmental Benefits: Lower chemical load to waste system. Lower odor during processing, DEGREASING OF LEATHER Environmental Benefits: Replaces solvent-based system, lowers volatile organic chemical load. PAPER INDUSTRY Environmental Benefits: Less chlorine bleach, therefore less chlorinated organics in the waste stream. DEINKING OF WASTE PAPER Environmental Benefits: Improved deinking creates more opportunity for recycled paper, less chemical discharge to waste streams, less wash water use, decreased load on landfills and a better utilization of natural resources.
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