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Chapter ten |
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Liquid Chromatography/Mass Spectrometry Analysis of Biosurfactant Glycolipids Secreted by Microorganisms
Alberto Nuñez, Robert A. Moreau, and Thomas A. Foglia
Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, PA 19038
Introduction
Biosurfactant glycolipids are compounds with a sugar residue linked to a lipid hydrophobic moiety by a glycosidic bond; their structures vary in size, complexity, and function and they are part of the larger family of glycoconjugates. Microorganisms such as yeasts and bacteria can secrete large amounts of simple extracellular glycolipids containing a mono- or disaccharide glycosylated to a hydroxy fatty acid (FA) (1). The amphiphilic structure of these products imparts to them surfactant-like properties that make them attractive bioemulsifiers in which there is growing commercial interest (2,3). Although strategies have been developed for their synthesis (4), the natural products secreted by microorganisms are usually preferred for marketing reasons (5). Most of these microorganisms produce a complex mixture of glycolipids and their structural identification requires sophisticated methods of analysis. In this sense, nuclear magnetic resonance (NMR) spectroscopy is usually a good option, but this method of analysis often requires tedious sample purification. Alternatively, mass spectrometry (MS) can provide information on glycolipid structures, especially if it is associated with a chromatographic separation technique. In general, glycolipids have molecular weights that are too large for gas chromatography (GC). The introduction of high performance liquid chromatography (HPLC) associated with mass spectrometry (LC/MS), however, has opened a new dimension in the analysis of glycolipids. Mass spectral characterization using ionization techniques such as electron impact (EI) causes extensive fragmentation of glycolipids, providing little information on molecular size or structural characteristics (6). On the other hand, “soft” ionization techniques such as atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) often permit the identification of pseudomolecular ions and a controlled degree of fragmentation. Using these two ionization methods it is often possible to obtain... |
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Modern Methods for Lipid AnalysiS by Liquid Chromatography/ mass spectrometry and Related Techniques |
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Resources for Lipid Analysis in the 21st Century |
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Contact the corresponding author:
Dr. Alberto Nunez Room 1203A 600 E. Mermaid Ln. ERRC Wyndmoor, PA, 19038-8598
E-mail: anunez@errc.ars.usda.gov Web address: |
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This was a sample page from the book to give you an idea of what is discussed. To learn more about APCI-MS for Sophorolipid Analysis, Buy the Book! |
