ERA

Download the full-sized PDF of Metabolism of lactic acid bacteria in wheat sourdough and bread qualityDownload the full-sized PDF

Analytics

Share

Permanent link (DOI): https://doi.org/10.7939/R37X23

Download

Export to: EndNote  |  Zotero  |  Mendeley

Communities

This file is in the following communities:

Graduate Studies and Research, Faculty of

Collections

This file is in the following collections:

Theses and Dissertations

Metabolism of lactic acid bacteria in wheat sourdough and bread quality Open Access

Descriptions

Other title
Subject/Keyword
Lactobacillus reuteri
glutaminase
ketoglutarate
propionic acid
Lactobacillus diolivorans
Lactobacillus buchneri
Lactobacillus sanfranciscensis
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Zhang, Chonggang
Supervisor and department
Michael Gänzle (Agricultural, Food and Nutritional Science)
Examining committee member and department
Dr. Thava Vasanthan, Department of Agricultural, Food and Nutritional Science
Dr. Michael Gänzle, Department of Agricultural, Food and Nutritional Science
Dr. Lynn McMullen, Department of Agricultural, Food and Nutritional Science
Dr. Ismail Fliss, Département des sciences des aliments et de nutrition, Université Laval
Dr. Karen Madsen, Department of Medicine
Dr. Lingyun Chen, Department of Agricultural, Food and Nutritional Science
Department
Department of Agricultural, Food, and Nutritional Science
Specialization

Date accepted
2011-09-26T15:55:44Z
Graduation date
2011-11
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Study on metabolism of lactic acid bacteria in wheat sourdough can improve bread quality such as bread flavour, texture and shelf life. This dissertation focused on several metabolic pathways in Lactobacillus strains on both biochemical and genetic level to fulfill three objectives. The first objective was to produce bread preservative propionate from lactate by cometabolism of Lactobacillus buchneri and Lactobacillus diolivorans to extend bread shelf life. The results showed that propionate was formed in cofermentation. Bread containing 20% sourdough from coferementation effectively inhibited growth of three of the four selected moulds for more than 12 days compared to traditional sourdough. The use of 10% experimental sourdough deferred growth of two molds by one day. The second objective was to characterize the metabolism of α-ketoglutarate (α-KG) in sourdough strains. Alpha-KG is an important amino group acceptor for flavour production during sourdough fermentation, however, knowledge on metabolism of α-KG in sourdough strains is lacking. Study of metabolism of α-KG in Lactobacillus sanfranciscensis and Lactobacillus reuteri showed that L. sanfranciscensis and L. reuteri utilized α-KG as electron acceptor, which was converted to 2-hydroxyglutarate in both media and wheat sourdough. The presence of phenylalanine and citrate in addition to α-KG partially redirected the use of α-KG from electron acceptor to amino group acceptor. The third objective was to compare the acid resistance pathways in L. reuteri 100-23. Inducible gene expressions for acid resistance are important survival strategy for Lactobacillus. Genes encoding three glutaminases in L. reuteri 100-23 were studied and compared with adi and gadB to find out the responsible acid resistance pathway under different acidic conditions. Under pH 3.5, ADI pathway is effective in acid resistance. Expression of gls3 was the highest during acid resistance among the three glutaminase genes. Analysis of gene expression in ∆gadB and ∆ gls3 strains showed that deletion of gadB resulted in over- expression of adi and gls3, whereas deletion of gls3 showed over-expression of gls1, gls2 and gadB compared to wild type strains. Gene expression in wheat sourdough showed comparable over-expression of gls3 and gadB.
Language
English
DOI
doi:10.7939/R37X23
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication

File Details

Date Uploaded
Date Modified
2014-04-30T22:18:45.045+00:00
Audit Status
Audits have not yet been run on this file.
Characterization
File format: pdf (Portable Document Format)
Mime type: application/pdf
File size: 1933443
Last modified: 2015:10:12 16:29:49-06:00
Filename: Ph. D thesis of Chonggang Zhang, Sep 21st, 2011.pdf
Original checksum: 39604b0b868159c7172aecb72c4bb8bd
Well formed: true
Valid: true
File author: Van Anh
Page count: 169
File language: en-CA
Activity of users you follow
User Activity Date