Abstract
Background Propionibacterium freudenreichii is an Actinobacterium widely used in the dairy industry as a ripening culture for Swiss-type cheeses, for vitamin B12 production and some strains display probiotic properties. It is reportedly a hardy bacterium, able to survive the cheese-making process and digestive stresses.ResultsDuring this study, P. freudenreichii CIRM-BIA 138 (alias ITG P9), which has a generation time of five hours in Yeast Extract Lactate medium at 30 °C under microaerophilic conditions, was incubated for 11 days (9 days after entry into stationary phase) in a culture medium, without any adjunct during the incubation. The carbon and free amino acids sources available in the medium, and the organic acids produced by the strain, were monitored throughout growth and survival. Although lactate (the preferred carbon source for P. freudenreichii) was exhausted three days after inoculation, the strain sustained a high population level of 9.3 log10 CFU/mL. Its physiological adaptation was investigated by RNA-seq analysis and revealed a complete disruption of metabolism at the entry into stationary phase as compared to exponential phase.Conclusions P. freudenreichii adapts its metabolism during entry into stationary phase by down-regulating oxidative phosphorylation, glycolysis, and the Wood-Werkman cycle by exploiting new nitrogen (glutamate, glycine, alanine) sources, by down-regulating the transcription, translation and secretion of protein. Utilization of polyphosphates was suggested.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3367-x) contains supplementary material, which is available to authorized users.
Highlights
Propionibacterium freudenreichii is an Actinobacterium widely used in the dairy industry as a ripening culture for Swiss-type cheeses, for vitamin B12 production and some strains display probiotic properties
Enumeration, DO, pH The results of bacterial enumerations and pH measurements (Fig. 1a) confirmed that CIRM-BIA 138 survived well during 11 days, even under conditions of nutritional shortage, as it had been observed during a previous study [13]
When inoculated at 7 log10 Colony forming unit (CFU)/mL, the P. freudenreichii culture entered the exponential growth phase to reach a maximum population of 9.3 log10 CFU/mL 3d post-inoculation, corresponding to entry into the stationary phase
Summary
Propionibacterium freudenreichii is an Actinobacterium widely used in the dairy industry as a ripening culture for Swiss-type cheeses, for vitamin B12 production and some strains display probiotic properties. It is reportedly a hardy bacterium, able to survive the cheese-making process and digestive stresses. Propionibacterium freudenreichii is an Actinobacterium widely used in the dairy industry and responsible for aroma development and opening (eyes) in Swiss-type cheeses. P. freudenreichii can produce ATP and NAD(P)H via fermentation utilizing an unique metabolic pathway (the Wood-Werkman cycle), leading to propionic acid. Several genes involved in polyphosphate and pyrophosphate utilization are found in the genome of CIRM-BIA1, the type strain for P. freudenreichii, suggesting a storage of energy in these forms [7].
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