Streptococcus thermophilus et Lactococcus lactis : des bactéries lactiques comme outils de production de peptides bioactifs ? Impact du système protéolytique sur la stabilité des peptides et production hétérologue d'un peptide anxiolytique, l'[alpha]-casozépine

Abstract : The designing of novel fermented milk products functionalized with bioactive peptides is one of the promising strategies to develop functional foods. The objective of the thesis is thus the development of fermented milks comprising of an anxiolytic peptide, alpha-casozepine (f91-100 of bovine alpha s1 CN) or its shorter fragment (f91 97). Firstly, we studied the stability of different bioactive peptides towards two strains, with PrtS+ (LMD¬9) and PrtS- (CNRZ1066) phenotypes, of S. thermophilus, a starter bacterium widely used for the manufacture of yogurt. It was revealed that both strains hydrolysed the peptides into shorter fragments by surface peptidases. The hydrolysis was neither due to intracellular peptidases eventually released from cell lysis nor to extracellular chaperone protease HtrA, since mutant LMD-9-deltahtrA also showed the same type of hydrolysis. Aminopeptidase, X-prolyl dipeptidyl peptidase, peptidyl dipeptidase and carboxypeptidase activities associated to the cell-surface of both strains were observed. Therefore, addition of bioactive peptides in fermented milks requires well prior characterization of the proteolytic potential of lactic acid bacteria. Finally, in order to add only one type of peptides instead of a peptide fraction, we expressed heterologously alpha-CZP in multimeric form in L. lactis using NICE system. It was revealed by ELISA test that a small quantity of recombinant alpha-CZP multimer was produced by both nisin-induced as well as non-induced cells. The significant decrease in the growth of nisin-induced recombinant L. lactis suggests that the peptide multimer has toxic effects on the cells
Document type :
Theses
File URL :
http://docnum.univ-lorraine.fr/prive/DDOC_T_2013_0184_HAFEEZ.pdf
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https://hal.univ-lorraine.fr/tel-01750439
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Submitted on : Thursday, March 29, 2018 - 12:46:15 PM
Last modification on : Friday, March 30, 2018 - 1:32:24 AM

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  • HAL Id : tel-01750439, version 1

Citation

Zeeshan Hafeez. Streptococcus thermophilus et Lactococcus lactis : des bactéries lactiques comme outils de production de peptides bioactifs ? Impact du système protéolytique sur la stabilité des peptides et production hétérologue d'un peptide anxiolytique, l'[alpha]-casozépine. Alimentation et Nutrition. Université de Lorraine, 2013. Français. ⟨NNT : 2013LORR0184⟩. ⟨tel-01750439⟩

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