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Physiological responses of bifidobacteria subjected to acid, cold and gastro-intestinal stress in organic and conventional milks

Abstract : Bifidobacteria are exposed to various stress, as a result of environmental conditions encountered during fermented milk production, cold storage and during digestion of the products inside gastrointestinal tract. In order to improve their survival, this study aimed at understanding the degradation mechanisms of the physiological state of various Bifidobacterium strains when exposed to cold, acid and in vitro simulated gastrointestinal stress. It also intended to establish relationships between stress resistance and milk and membrane fatty acids contents, in organic and conventional milks. The results showed that acidification activity of bifidobacteria was strain-dependent and increased when bifidobacteria were associated to yogurt cultures, when organic milk was used and when incubation temperature was set at 42°C instead of 37°C. Cultivability and survival of the Bifidobacterium strains were determined after fermentation, after storage at 4°C for 7 to 28 days, and during in-vitro digestion that was simulated in a dynamic gastrointestinal tract model. These characteristics were improved in organic fermented milks as compared to conventional products, when fermentation was performed at 42°C until pH 4.4, and when the fermented milks were kept at 28°C for 12 hours before being cooled to 4°C. These specific manufacture procedures thus generated physiological adaptation of the bifidobacteria to the stress. During in-vitro digestion, cultivability of bifidobacteria was less deteriorated when they were grown in organic instead of conventional milk, and to a less extent, when the adaptation procedures were applied during fermented milk manufacture. These results were related to the higher unsaturated fatty acids content, including trans-vaccenic, conjugated linoleic and α-linoleic acids that characterize organic products. These particular fatty acids profiles of organic milks allowed bifidobacteria to modify their membrane fatty acids composition, by increasing their unsaturated fatty acids contents and by shortening the length of medium chain saturated fatty acids, thus adapting their membrane fluidity. When specific manufacture procedures were carried out to trigger physiological adaptation of the bifidobacteria, membrane fatty acid composition changed différently from what is observed in organic milk. This difference indicates that other biological adaptation mechanisms are probably involved, especially at the proteomic level. Finally, this study demonstrated that modifications at membrane level contribute to modulate resistance against technology and gastro-intestinal stress of Bifidobacterium strains to better withstand technological and gastro-intestinal stress.
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Submitted on : Friday, August 1, 2014 - 12:44:09 PM
Last modification on : Friday, August 5, 2022 - 2:38:10 PM
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  • HAL Id : pastel-01053733, version 1


Ana Carolina Rodrigues Florence. Physiological responses of bifidobacteria subjected to acid, cold and gastro-intestinal stress in organic and conventional milks. Microbiology and Parasitology. AgroParisTech, 2013. English. ⟨NNT : 2013AGPT0033⟩. ⟨pastel-01053733⟩



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