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Παραγωγή βιοτασιενεργών ουσιών με χρήση βαρέων κλασμάτων αργού πετρελαίου ως πηγή άνθρακα

Mandalenaki Athina

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Year 2016
Type of Item Diploma Work
Bibliographic Citation Αθηνά Μανδαλενάκη, "Παραγωγή βιοτασιενεργών ουσιών με χρήση βαρέων κλασμάτων αργού πετρελαίου ως πηγή άνθρακα", Διπλωματική Εργασία, Σχολή Μηχανικών Περιβάλλοντος, Πολυτεχνείο Κρήτης, Χανιά, Ελλάς, 2016
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Every year, human activities release between 190 and 706 million gallons of crude oil or refined petroleum products in the sea. The components which dissolve in the water contain a variety of compounds which are toxic to a wide range of marine organisms. There are several methods for cleaning up an oil spill. Booms and skimmers are generally the first choice but can only remove a portion of the spill, which ranges from 10 to 15% when the method is applied shortly after the leak. Hence, it is necessary to implement secondary mechanisms to remove the remaining part of the spill. Bioremediation is the most ‘green’ method for this purpose (bioremediation can also be used as primary method when it is impossible to use mechanic methods). According to the United States EPA (Environmental Pollution Agency), bioremediation is a “treatment that uses naturally occurring organisms to break down hazardous substances into less toxic or non-toxic substances”. Biodegradation of oil is one of the most important processes included in oil weathering and in the final cleanup of the environment, specifically when it comes to the non-volatile components of oil. It is proven that more than 200 species of bacteria and fungi have the ability to degrade hydrocarbons consisting of 10 to 40 carbon atoms.The main purpose of this thesis was to produce biosurfactants of high quality. The carbon source used in the cultures was heavy fraction of crude oil. This fraction has the characteristic that it forms a kind of a solid layer on the surface of the liquid. Because of its difficulty to get dissolved in the water, the idea was created that surfactants isolated from the liquid would not have any oil impurities.The bacteria used for this thesis were derived from a sea area polluted with oil. These microorganisms are 1) a microbial community whose phylogenetic tree is shown in Figure 10, 2) the isolated microorganism Alcanivorax borkumensis SK2 and 3) the isolated microorganism Paracoccus marcusii. All of these microorganisms have the ability to produce biosurfactants and to degrade hydrocarbons. Surfactants are usually organic compounds that are amphiphilic, meaning they contain both hydrophobic groups (their tails) and hydrophilic groups (their heads). Surfactants will diffuse in water and adsorb at interfaces between oil and water reducing thus, the surface tension of the solution. Hence, adding surfactants in areas which are polluted with petroleum increases the solubility of hydrocarbons and like this, the bioavailability of them. By increasing the bioavailability of the oil, it is much easier for the microorganisms to biodegrade it. The biosurfactants which have been isolated during the experiments of this thesis are characterized to be Rhamnolipids which is a category of Glycolipids. Nowadays, Rhamnolipids are considered to be the most effective types of biosurfactants. The solution in which the microorganisms were cultured consisted of artificial seawater ONR7, nutrients such as nitrogen and phosphorus, and heavy crude oil fractions. From the microorganisms which were used, Alcanivorax borkumensis SK2 is the one that produces the highest concentration of Ramnolipids. This concentration is 52,5g/L and its production takes place after 22 days. Furthermore, included in this thesis are the descriptions of some possible applications for every microorganism.

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