Mass Spectrometric Analysis of Bioactive Metabolites from Lactobacilli

  • Author / Creator
    Black, Brenna A
  • Lactobacilli are commonly used in food fermentations. Preservation and changes in food quality due to fermentation arise because of the growth, metabolism and enzymatic activity of these organisms. Enzymatic pathways of lactobacilli can also be exploited for the production of bioactive compounds. In this work, Lactobacillus spp. were used to enzymatically produce hydroxy fatty acids with anti-fungal activities and oligosaccharides with anti-adhesion properties. These bioactive compounds were found to be present as mixtures of geometric and positional isomers. In order to characterize individual isomers with minimal preparatory steps, liquid chromatography/tandem mass spectrometry (LC-MS/MS) methods were developed.
    Lactobacillus hammesii and Lactobacillus plantarum converted linoleic acid into a racemic mixture of anti-fungal 10-hydroxy-cis-12-octadecenoic and 10-hydroxy-trans-12-octadecenoic acid by means of hydratase enzymes. When produced in sourdough bread 10-hydroxy-12-octadecenoic acid and anti-fungal 13-hydroxy-cis-9,trans-11-octadecadienoic acid, the latter which is enzymatically formed by flour lipoxygenase in the presence of reducing agents, increased the mould-free storage-life of the bread. Results from LC-MS/MS methods allowed for conversion pathway elucidation of linoleic acid to conjugated linoleic acid by lactobacilli.
    Lactobacillus spp. containing galactosidase enzymes were used to form composite oligosaccharides with anti-adhesive properties. Using LC-MS/MS analysis, several novel oligosaccharides formed by β- and α-galactosidase were identified. In particular, Galβ-(1→4)-GlcNAc was formed, which is the core structure in human milk oligosaccharides and acts as a competative inhibitor to enteropathogenic Escherichia coli.
    The LC-MS/MS methods developed in this work proved useful in investigating structure-function relationships of anti-fungal lipids and anti-adhesive oliogsaccharides. This research can be further applied to increase the variety of bioactive compounds identified for food protection and health promotion.

  • Subjects / Keywords
  • Graduation date
    Fall 2013
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.