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Development of Microorganisms with Improved Biosurfactant Activity

Bagheri Lotfabad, Tayebe | 2009

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 39501 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Roosta Azad, Reza; Rouholamini Najafabadi, Abdolhossein; Akbari Noghabi, Kambiz; Shahcheraghi, Fereshte
  7. Abstract:
  8. This thesis discusses the work on the production of a rhamnolipid-type biosurfactant by Pseudomonas aeruginosa MR01, its structural characterization and environmental applications. First, results from analytical approaches for screening of biosurfactant producers suggested the oil spreading method as the fastest, simplest and most consistent analytical method. The second part of the thesis describes the properties of the most efficient biosurfactant-producing bacteria isolated from oil fields in south of Iran and according to it’s biochemical characteristics and partial sequenced 16S rRNA gene affiliated with Pseudomonas aeruginosa. Time course study indicated that the maximum biosurfactant production occurred and established in the stationary growth phase (after 84 h). The best production of 2.5-2.7 g/l was obtained when the cells were grown on minimal salt medium containing 1% (v/v) olive oil and 0.1% (w/v) sodium nitrate supplemented with 0.1% (w/v) isoleucine at 37 ºC and 200 rpm after 84 h. The MR01 could reduce surface tension to 28 mN/m and emulsified hexadecane up to E24≈70%. The core holder biosurfactant flooding experiments demonstrated that the oil recovery efficiencies varied from 23.7% to 27.1% of residual oil. Fourier Transform Infrared spectrum of extracted biosurfactant indicated the presence of carboxyl, carbonyl and hydroxyl functional groups and rhamnose bands. The extracted biosurfactant was analyzed by thin-layer chromatography (TLC) and revealed the presence of two glycolipid compounds. The structure elucidation of these isolated fractions using 1H nuclear magnetic resonance (NMR) spectroscopy confirmed by the structural variants that exist in the literature for rhamnolipid species. Additional analyzing with liquid chromatography/mass spectrometry (LC/MS) demonstrated that the purified product was a mixture of seventeen different rhamnolipid congeners. Gamma ray mutagenesis created a novel mutant of MR01 strain demonstrated more than one and a half fold increment in biosurfactant production and activity compared to the wild type strain. Rhamnolipid production yield rised to 10 to 12g/l in soybean oil medium
  9. Keywords:
  10. Pseudomonas Aeruginosa Bacteria ; Chemical Analysis ; Oil Recovery ; Rhamnolipid Biosurfactant ; Mutant

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