Solution and Interfacial Characterization of Rhamnolipid Biosurfactant from P.aeruginosa ATCC 9027

Persistent Link:
http://hdl.handle.net/10150/193778
Title:
Solution and Interfacial Characterization of Rhamnolipid Biosurfactant from P.aeruginosa ATCC 9027
Author:
Lebron-Paler, Ariel
Issue Date:
2008
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Rhamnolipid biosurfactants are investigated to determine their role in biological processes, and for discovery of novel, more biocompatible applications in areas related to medicine, agriculture, and environment. Fundamental understanding of the physical and chemical properties of rhamnolipids is needed. Thus, systematic studies on solution and interfacial properties on rhamnolipids from P.aeruginosa ATCC 9027 were undertaken. A purification protocol was developed and a thorough qualitative and quantitative speciation analysis was performed with high performance liquid chromatography-mass spectrometry (HPLC-MS), nuclear magnetic resonance (NMR) spectroscopy and HPLC with evaporative light scattering detection (ELSD). Acid-base properties of the mixture of 30 monorhamnolipid congeners, including both saturated and unsaturated species, were characterized at concentrations below and above the CMC at fixed ionic strength using potentiometry and attenuated total reflectance-Fourier transform infrared (ATRFTIR) spectroscopy. A pKₐ of 4.3 was found for concentrations below 50 μM and a pKₐ of 5.6 above 100 μM. The pKₐ is dictated by aggregation in solution. Molecular areas of monorhamnolid monolayers at the air-water interface are strongly influenced by protonation state, and increase from 31 to 109 Ų/molecule as pH increases from 4 to 8.5 and as ionic strength decreases. Adsorption isotherms of monorhamnolipids on γ-Al₂O₃ were investigated as a function of pH using ATR-FTIR spectroscopy and Frumkin model fits, from which K(ads) values of 1.20 (± 0.10) x 10⁵ M⁻¹ at pH 4.0, 2.14 (± 0.51) x 10⁴ M⁻¹ at pH 6.3 and 1.31 (± 0.09) x 10³ M⁻¹ at pH 8.6 were obtained. Interaction parameters were positive at all pH values. Cooperative adsorption is driven by hydrophobic interactions (physisorption) at any pH including hydrogen bonding and electrostatic interactions. Chemisorption was also observed at high pH values. Formation constants for monorhamnolipid-Pb²⁺ and monorhamnolipid-Cd²⁺ complexes were determined using differential pulse polarography in the low μM concentration range. A modified Lingane equation was developed to account for monorhamnolipid adsorption on the Hg surface. β values for adsorbed metal complexes are ~10^3.2 and ~10^0.8 for Pb²⁺ and Cd²⁺, respectively, compared to previously published β values of 10^8.58 and 10^6.89, respectively. Evidence for 1:1 and 2:1 monorhamnolipid-metal complexes was provided by electrospray ionization-mass spectrometry.
Type:
text; Electronic Dissertation
Keywords:
bioremediation; biosurfactant; P.aeruginosa; rhamnolipids
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Chemistry; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Pemberton, Jeanne E.
Committee Chair:
Pemberton, Jeanne E.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleSolution and Interfacial Characterization of Rhamnolipid Biosurfactant from P.aeruginosa ATCC 9027en_US
dc.creatorLebron-Paler, Arielen_US
dc.contributor.authorLebron-Paler, Arielen_US
dc.date.issued2008en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractRhamnolipid biosurfactants are investigated to determine their role in biological processes, and for discovery of novel, more biocompatible applications in areas related to medicine, agriculture, and environment. Fundamental understanding of the physical and chemical properties of rhamnolipids is needed. Thus, systematic studies on solution and interfacial properties on rhamnolipids from P.aeruginosa ATCC 9027 were undertaken. A purification protocol was developed and a thorough qualitative and quantitative speciation analysis was performed with high performance liquid chromatography-mass spectrometry (HPLC-MS), nuclear magnetic resonance (NMR) spectroscopy and HPLC with evaporative light scattering detection (ELSD). Acid-base properties of the mixture of 30 monorhamnolipid congeners, including both saturated and unsaturated species, were characterized at concentrations below and above the CMC at fixed ionic strength using potentiometry and attenuated total reflectance-Fourier transform infrared (ATRFTIR) spectroscopy. A pKₐ of 4.3 was found for concentrations below 50 μM and a pKₐ of 5.6 above 100 μM. The pKₐ is dictated by aggregation in solution. Molecular areas of monorhamnolid monolayers at the air-water interface are strongly influenced by protonation state, and increase from 31 to 109 Ų/molecule as pH increases from 4 to 8.5 and as ionic strength decreases. Adsorption isotherms of monorhamnolipids on γ-Al₂O₃ were investigated as a function of pH using ATR-FTIR spectroscopy and Frumkin model fits, from which K(ads) values of 1.20 (± 0.10) x 10⁵ M⁻¹ at pH 4.0, 2.14 (± 0.51) x 10⁴ M⁻¹ at pH 6.3 and 1.31 (± 0.09) x 10³ M⁻¹ at pH 8.6 were obtained. Interaction parameters were positive at all pH values. Cooperative adsorption is driven by hydrophobic interactions (physisorption) at any pH including hydrogen bonding and electrostatic interactions. Chemisorption was also observed at high pH values. Formation constants for monorhamnolipid-Pb²⁺ and monorhamnolipid-Cd²⁺ complexes were determined using differential pulse polarography in the low μM concentration range. A modified Lingane equation was developed to account for monorhamnolipid adsorption on the Hg surface. β values for adsorbed metal complexes are ~10^3.2 and ~10^0.8 for Pb²⁺ and Cd²⁺, respectively, compared to previously published β values of 10^8.58 and 10^6.89, respectively. Evidence for 1:1 and 2:1 monorhamnolipid-metal complexes was provided by electrospray ionization-mass spectrometry.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectbioremediationen_US
dc.subjectbiosurfactanten_US
dc.subjectP.aeruginosaen_US
dc.subjectrhamnolipidsen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineChemistryen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorPemberton, Jeanne E.en_US
dc.contributor.chairPemberton, Jeanne E.en_US
dc.contributor.committeememberMaier, Raina M.en_US
dc.contributor.committeememberArmstrong, Neal R.en_US
dc.contributor.committeememberBrusseau, Mark L.en_US
dc.contributor.committeememberWysocki, Vicki H.en_US
dc.identifier.proquest10169en_US
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