Effet de la digestion gastrique sur la viabilité et l'expression de gènes de stress de bactéries probiotiques dans une matrice de sève d'érable

Authors: Hamelin, Laurie
Advisor: Roy, Denis; Roblet, Cyril Roland
Abstract: The probiotic bacteria must be able to survive during gastric digestion in order to reach the colon and thus provide human health benefits. The potential of dairy matrices to support probiotics hasoften been described, but plant products such as maple sap for this application remains little known,while the interest for these products is growing. The objective of this thesis was to evaluate cell viability by the use of propidium monoazide (PMA) coupled to qPCR, as well as to evaluate the expression offive genes linked to stress atpA, dnaK, galK, groEL and hrcA by RT-qPCR during in vitro gastricdigestion (TIM-1) of three commercial strains (Bifidobacterium animalis ssp. lactis A026,Lacticaseibacillus paracasei A234, Lacticaseibacillus rhamnosus A119) as well as the reference strain Lacticaseibacillus rhamnosus GG (ATCC 53103) delivered in maple sap. The results indicated that all strains maintained a high survival rate after gastric digestion; B. animalis subsp. lactis A026 (7.14 log ofviable cells/mL), L. paracasei A234 (8.12 log of viable cells/mL), L. rhamnosus A119 (8.48 log of viablecells/mL), and L. rhamnosus GG (8.36 log of viable cells/mL) and that the expression of certain target stress genes was modulated during gastric digestion. Only L. rhamnosus GG strain showed modulationin the expression of all target genes. Overall, the expression of at least one gene associated with the stress response was modulated for all probiotic strains during gastric digestion in the maple sap matrix. Faced with the stress of gastric digestion, the different responses of the metabolism of probiotic bacteria allow better cell survival. Ultimately, these four strains have the potential to be used asprobiotics in a maple sap matrix, which could lead to the development of a functional drink.
Document Type: Mémoire de maîtrise
Issue Date: 2021
Open Access Date: 5 July 2021
Permalink: http://hdl.handle.net/20.500.11794/69523
Grantor: Université Laval
Collection:Thèses et mémoires

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