Effect Of Probiotic Bacteria On The Conjugated Linoleic Acid Cla Content And Quality Of Yogurt

Author : Eva Rosberg-Cody
Publisher :
ISBN 13 :
Total Pages : 232 pages
Book Rating : 4.:/5 (795 download)

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Download or read book Genetic and Functional Analysis of Conjugated Linoleic Acid Production in Bifidobacteria and Lactic Acid Bacteria written by Eva Rosberg-Cody and published by . This book was released on 2008 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: The overall aims of this thesis were to gain an increased insight into the role and implications of bacterial CLA production both in relation to host health, and also examine the physiological role of CLA production from the bacteria point of view. Initially, we screened neonatal bifidobacteria from faeces of infants with different case histories, e. g full-term/preterm, breast-/formula-fed, in order to isolate novel CLA producing strains. The most commonly isolated strain was Bifidobacterium breve, which were also the most efficient CLA producers. In a subsequent study, we localized, amplified, cloned and overexpressed the putative c9, t11 CLA isomerase from Bifidobacterium breve in both Lactococcus lactis and Corynebacterium glutamicum. The resultant recombinant strains however, showed no isomerise activity, but did convert linoleic acid to hydroxy fatty acids, believed to be intermediates in CLA production. Interestingly, structural comparisons revealed that the putative c9, t11 isomerase and the t10, c12 isomerase from Propionibacterium acnes have almost identical structures. In addition, clones expressing the putative c9, t11 CLA isomerise exhibited increased tolerance to a number of environmental stress including heat and that associated with solvent exposure. In another study, the t10, c12 CLA isomerase from Propionibacterium acnes was cloned and overexpressed in Lactococcus lactis and Escherichia coli. The resultant recombinant strains could convert the substrate linoleic acid to t10, c12 CLA. Indeed, t10, c12 CLA extracted from recombinant lactococci was shown to be strongly anti-proliferative against SW480 colon cancer cells. To investigate if the observed increased tolerance to stress by recombinant strains carrying the putative c9, t11 CLA isomerase also could be observed for clones carrying the active t10, c12 CLA isomerase, recombinant Lactococcus lactis heterologously expressing the t10, c12 CLA isomerase, along with vector controls of Lactococcus were exposed to normally lethal levels of heat, solvent and salt stresses. The results demonstrated that recombinant Lactococcus expressing the isomerase displayed a 100-fold increased survival, which was even more pronounced in the presence of substrate linoleic acid. This increased tolerance to environmental stresses of strains which express the isomerase may be due to changes in membrane fluidity as a result of incorporation of conjugated fatty acids. Finally, the active t10, c12 CLA isomerase was cloned and overexpressed in probiotic Lactobacillus paracasei NFBC 338 (Lb 338) and used in a mice feeding trial together with the substrate linoleic acid. This resultant strain produced CLA in vivo, as shown by a 4-fold increase of the conjugated isomer in adipose tissue compared with mice fed a control strain. To investigate the impact of pure t10, c12 CLA on mice fatty acid profile, this isomer was fed to mice which resulted in many changes in the fatty acid profile, most notably, a 300-700 % increase in the beneficial omega-3 fatty acids, EPA, DPA and DHA in most tissues.