2007-2008 b iotechnology. b. biological fuels 1the need for biological fuels 2raw materials these...

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  • 2007-2008 B IOTECHNOLOGY
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  • B. BIOLOGICAL FUELS 1The need for biological fuels 2Raw materials These include wastes and crops; wastes Dry Wastes Wet wastes Crops In the future, crops may be grown specially for energy production, perhaps on land unsuitable for growing foodstuffs. Sugar ca ne is already being grown in Brazil for this purpose.
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  • A. ETHANOL PRODUCTION 1- Substrates include sugar cane, cassava roots, cellulose waste and corn. Cassava roots contain starch which must be hydrolysed to sugars, and cellulose waste, such as timber and straw, needs quite complex pre-treatment with ligno-cellulase enzymes or chemicals. 2- At present, alcohol production is similar to the traditional process but much research is taking place.
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  • It is hoped that more efficient, genetically engineered M.O.s will be developed and that newer fermentor designs and immobilized enzyme technology will improve efficiency. 3- Distillation costs can be reduced by using a cheap fuel, and bagasse (the waste from sugar cane) has proved to be an economical fuel for raising steam for the process by combustion.
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  • 4- A range of M.O.s have been used in the production of ethanol, using many different carbohydrates as substrate. Traditionally, ethanol production has relied upon the use of yeasts, mostly Saccharomyces species. 5- Zygomonas mobilis has been used in South America for many years in the production of tequila, and in Indonesia and Africa to make palm wine.
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  • However, its use in the western world is quite new. Recent research into Zygomonas has shown that it is more efficient than yeasts in converting sugar to ethanol. 6- A technique has been developed to produce ethanol using Zygomonas in a continuous culture process, rather than the more traditional batch culture methods.
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  • 6.4The production of methane (1) Sewage (2) Urban waste, landfill gas (3) Biogas fermentors However, while this is a useful small-scale process, it is unlikely to be commercially avaible on a large scale because : methane can be produced far more cheaply from coal at present;
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  • natural gas is cheaper than microbially produced methane. There are many natural sources of methane Gas is expensive to store, transport and distribute at present. It is expensive and difficult to liquefy.
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  • (4) Agricultural wastes Some farms now place animal manure and other crop residues into anaerobic digestion tanks. Here, the waste is fermented by M.O.s and the methane produced is collected, liquefied and used to power farm machinery. In some cases it may be used to fire boilers, which heat glasshouses and produce early crops of tomatoes, peppers and other vegetables.
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  • C. P HARMACEUTICALS PRODUCED BY M.O. S : 1. Dextrans Dextrans are polysaccharides produced by lactic acid bacteria, in particular members of the genus Leuconostoc (e.g. L. dextranicus and mesenteroides ) following growth on sucrose.
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  • 2- Vitamins, amino acids and organic acids 1. Vitamins Vitamin B2 ( riboflavin ) is a constituent of yeast extract and incorporated into many vitamin preparations. Vitamin B2 deficiency is characterized by symptoms which include an inflamed tongue, dermatitis and a sensation of burning in the feet.
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  • 2. Amino acids Amino acids find applications as ingredients of infusion solutions for parenteral nutrition and individually for treatment of specific conditions. They are obtained either by fermentation processes similar to those used for antibiotics or in cell-free extracts employing enzymes isolated from bacteria.
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  • 3. Organic acids Examples of organic acids (citric, lactic, gluconic) produced by M.O.s. Citric and lactic acids also have widespread uses in the food and drink and plastics industries, respectively. Gluconic acid is also used as a metal- chelating agent in, for example, detergent products.
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  • 3 Iron-chelating agents Growth of many M.O.s in iron-deficient growth media results in the secretion of low molecular weight iron-chelating agents called siderophores, which are usually phenolate or hydroxamate compounds. -The therapeutic potential of these compounds has generated considerable interest in recent years.
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  • 4 Enzymes 1- Streptokinase and streptodornase Mammalian blood will clot spontaneously if allowed to stand : however, on further standing, this clot may dissolve as a result of the action of a proteolytic enzyme called plasmin. Plasmin is normally present as its inactive precursor, plasminogen.
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  • Streptokinase is administered by intravenous or intra-arterial infusion in the treatment of thrombo-embolic disorders.
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  • 2 - L-Asparaginase - L- Asparaginase, an enzyme derived from E. coli or Erwinia carotovora, has been employed in cancer chemotherapy where its selectivity depends upon the essential requirement of some tumors for the amino acid L-asparagine. - Normal tissues do to require this amino acid and thus the enzyme is administered with the intention of depleting tumor of asparagine by converting it to aspartic acid and ammonia.
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  • 3 - Neuraminidase - Neuraminidase derived from Vibrio cholerae has been used experimentally to increase the immunogenicity of tumour cells. -It is capable of removing N-acetylneuraminic ( sialic ) acid residues from the outer surface of certain tumor cells, thereby exposing new antigens which may be tumor specific together with a concomitant increase in their immunogenicity.
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  • - -In lab animals administration of neuraminidase-treated tumour cells was found to be effective against a variety of mouse leukaemias.
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  • 4 -Lactamases - -Latamase enzymes, whilst being a considerable nuisance because of their ability to confer bact. resistance by inactivating penicillins and cephalosporins are useful in the sterility testing of certain antibiotics and, prior to culture, in inactivating various -lactams in blood or urine samples in patients undergo therapy with these drugs.
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  • - One other important therapeutic application is the rescue of patients presenting symptoms of a sev e re allergic reaction following administration of a - lactamase - sensitive penicillin.
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  • 3- A PPLICATIONS OF M.O. S IN THE PARTIAL SYNTHESIS OF PHARMACEUTICALS : 3.1 Production of antibiotics Alexander Fleming's accidental discovery of penicillin in 1929 is well known. He found the mould Penicillium notatum contaminating a Petri dish of pathogenic bacteria and inhibiting their growth.
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  • He isolated penicillin but it was not until the Second World War that it was successfully produced on a large scale. At first, it was grown in static liquid culture in flasks, shallow pans and bottles, but this process was inefficient and it was not possible to produce enough penicillin to meet demand.
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  • Two theories have been proposed to explain antibiotic production. 1- Antibiotics are secondary metabolites, so they may be produced to keep enzyme systems operative when the microbe has run out of nutrients and cell division is no longer possible. Normally, when the substrate has been used up, the enzymes of that particular pathway would be broken down.
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  • - Then, if a new nutrient supply was found, there would be a delay while the necessary enzymes were produced. - It has been suggested that making a secondary metabolite keeps the enzymes active, so that the microbe can quickly take advantage of any new food supply. - 2- Some scientists think antibiotic production is for ridding of the cell toxic metabolic waste.
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  • - - Although not toxic to the organism producing them, these substances could still be highly toxic to other M.O.s. - If the toxin phenylacetic acid is added to a culture of Penicillium, penicillin production is increased. This observation supports this theory. - It is of course, possible that both theories are correct since they are not contradictory.
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  • T HE INDUSTRIAL PRODUCTION OF ANTIBIOTICS ; PENICILLIN PRODUCTION 1- M.O. the organism used for production of penicillin was Penicillium notatum, but the mostly common used is P. chrysogenus. 2- Inoculum Preparation ; a pure inoculum in sufficient volume and in the fast growing ( logarithmic ) phase so that a high population density is soon obt a ined.
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  • 3- The fermenter ; A typical fermenter is closed, vertical, cylinderical, stainless steel vessel with convexly dished ends and 25 - 250 m3 capacity. The height is usually two to three times its diameter. 4- Oxygen supply ; Penicillin fermentation need oxygen, which is supplied as filtered sterilised air from a compressor.
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  • 5- Temperature control ; The production of penicillin G is very sensitive to temperature, the tolerance being less than 1 C. Heat is generated both by the metabolism of nutrients and by the power dissipated in stirring, and has to by removed by controlled cooling. 6- Defoaming agents ; The fermenter system stirred vigorously and aerated usually foam, so provision has to made for adding