Article

Florence Algaron, Guy Miranda, Dominique Le Bars, Véronique Monnet
2003 Le Lait  
The proteolytic system of lactic acid bacteria has been characterised in detail and numerous modified strains with null or increased specific proteolytic activities have been constructed or identified among natural strains. Based on this knowledge, our objective was to ferment milk with modified strains and produce mixtures of peptides with specific features corresponding to potential bio-activities. We used a collection of Lactococcus lactis negative mutants for peptidase activities available
more » ... tivities available in the laboratory to ferment the milk. In particular, we focused our work on mutants lacking either aminopeptidase N, X-prolyl dipeptidyl aminopeptidase or tripeptidase in order to test their ability to form peptides with immunomodulating or antihypertensive activities. At the end of fermentation, supernatants were fractionated by RP-HPLC. Each fraction collected was analysed by Maldi-Tof MS and sequencing. We observed that mutants accumulated specific peptides consistent with the specificity of the missing peptidases. Some of the peptides identified present similarities with peptides having immunomodulating or anti-hypertensive effects. One of these was quantified. At the same time, we observed that the inhibition of angiotensin converting enzyme was stronger in supernatants obtained with mutant strains than in supernatant obtained using the wild-type strain. In conclusion, we showed that in some cases, modifications to the proteolytic system of Lactococcus lactis gave rise to significant differences in the mixtures of peptides produced during milk fermentation. The differences in bio-activity of these peptide mixtures were only partially determined in vitro and evidently need to be demonstrated in vivo. Exploitation of the biodiversity of the proteolytic system of lactic acid bacteria may enable a direct application of this work and undoubtedly a promising means of directly producing natural bio-active peptides in fermented milk products. Milk fermentation / Lactococcus lactis / bio-active peptide / proteolysis / mutant Résumé -Conséquences de modifications du système protéolytique de Lactococcus lactis sur l'accumulation de peptides potentiellement bio-actifs pendant la fermentation du lait. Le système protéolytique des bactéries lactiques a été caractérisé en détail et de nombreuses souches aux activités protéolytiques modifiées ont été construites ou identifiées parmi des souches sauvages. Notre objectif est de produire des mélanges de peptides ayant des activités biologiques, en utilisant ces souches modifiées pour fermenter le lait. Pour cela, nous avons utilisé une collection de mutants de Lactococcus lactis dont certaines activités peptidasiques ont été supprimées. En particulier, nous nous sommes intéressés à des souches n'ayant plus l'aminopeptidase N, la X-prolyl-dipeptidyl aminopeptidase, ou la tripeptidase pour tester leur aptitude à former des peptides ayant des activités * Corresponding author: algaron@jouy.inra.fr 116 F. Algaron et al.
doi:10.1051/lait:2003034 fatcat:lsd64ztfhza5jawzxrwea26za4