Système protéolytique de surface de "streptococcus thermophilus" : variabilité des capacités d'hydrolyse des caséines : caractérisation d'un nouveau système de transport de peptides

Abstract : S. thermophilus is a widely used bacterium in the manufacture of dairy products. The capacity of S. thermophilus to generate bioactive peptides from bovine caseins was studied. Ten strains expressing different levels of the cell envelope protease, PrtS, were incubated with [alpha]s1-, [alpha]s2- or [beta]-casein. Number and type of peptides released were strain-dependent. Peptides known as bioactive peptides were detected: 13 peptides were generated from [beta]-casein, 5 peptides from [alpha]s2-casein and 2 peptides from [alpha]s1-casein. The use of this bacterium for the production of such peptides in the food products requires the least internalization of these peptides by this bacterium. We were interested in knowing the peptide transport system present in the species S. thermophilus. A collection of 22 strains of S. thermophilus was chosen to study the genetic variability of peptide transport systems present within the species. First of all, we evaluated the phylogenetic proximity between selected strains by MLST, and then the genetic variability of the transport system of oligopeptides Ami and di- and tripeptides transporter, DtpT were studied in this collection. A cluster consisting of four genes, annotated as ABC transporter of peptides and nickel was detected in the genome of strain LMD-9, and called Ots. It is present in 9 of 22 strains of S. thermophilus and is transcribed throughout the growth in M17 medium. The Ots system seems to be involved in the internalization of smaller sized peptides
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Nawara Jameh Galia. Système protéolytique de surface de "streptococcus thermophilus" : variabilité des capacités d'hydrolyse des caséines : caractérisation d'un nouveau système de transport de peptides. Alimentation et Nutrition. Université de Lorraine, 2012. Français. ⟨NNT : 2012LORR0197⟩. ⟨tel-01749262⟩

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