Dynamic analysis of <Emphasis Type="Italic">Lactobacillus delbrueckii</Emphasis> subsp. <Emphasis Type="Italic">bulgaricus</Emphasis> CFL1 physiological characteristics during fermentation |
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Authors: | Aline Rault Marielle Bouix Catherine Béal |
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Institution: | (1) AgroParisTech, INRA, UMR 782 Génie et Microbiologie des Procédés Alimentaires, CBAI, 78850 Thiverval-Grignon, France;(2) ARILAIT Recherches, 42 rue de Chateaudun, 75314 Paris cedex 09, France |
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Abstract: | This study aimed at examining and comparing the relevance of various methods in order to discriminate different cellular states
of Lactobacillus bulgaricus CFL1 and to improve knowledge on the dynamics of the cellular physiological state during growth and acidification. By using
four fluorescent probes combined with multiparametric flow cytometry, membrane integrity, intracellular esterase activity,
cellular vitality, membrane depolarization, and intracellular pH were quantified throughout fermentations. Results were compared
and correlated with measurements of cultivability, acidification activity (Cinac system), and cellular ability to recover
growth in fresh medium (Bioscreen system). The Cinac system and flow cytometry were relevant to distinguish different physiological
states throughout growth. Lb. bulgaricus cells maintained their high viability, energetic state, membrane potential, and pH gradient in the late stationary phase,
despite the gradual decrease of both cultivability and acidification activity. Viability and membrane integrity were maintained
during acidification, at the expense of their cultivability and acidification activity. Finally, this study demonstrated that
the physiological state during fermentation was strongly affected by intracellular pH and the pH gradient. The critical pHi
of Lb. bulgaricus CFL1 was found to be equal to pH 5.8. Through linear relationships between dpH and cultivability and pHi and acidification
activity, pHi and dpH well described the time course of metabolic activity, cultivability, and viability in a single analysis. |
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Keywords: | Lactic acid bacteria Physiological state Viability Acidification activity Flow cytometry |
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