Peptidase activities in different strains of Lactobacillus helveticus.

Special Symposium - Innovations in Food Technology (LMC Congress)

Innovations in Food Technology - Poster Session (LMC/Food - P1)

MSc Marie Penderup Jensen
Copenhagen University
Dpt. of Food Science; Faculty of Life Sciences
Rolighedsvej 30, 5.
1958 Frederiksberg C
Denmark

Asc. Prof Finn Kvist Vogensen
University of Copenhagen
Dpt. of Food Science, Faculty of Life Sciences
Rolighedsvej 30, 5.
1958 Frederiksberg C
Denmark

Prof Ylva Ardö
Faculty of Life Sciences, copenhagen University
Department of Food Science, Dairy Technology
Rolighedsvej 30
DK-1958 Frederiksberg C
Denmark

Keywords: Lactobacillus helveticus, Peptidase activities, Strain dependence, Synthetic substrates

Background
Lactobacillus helveticus is a fastidious lactic acid bacterium that is auxotrophic for several amino acids. In order to grow in milk Lb. helveticus is dependent on its proteolytic/peptidolytic system for the release of essential amino acids. The proteolytic and the peptidolytic activities as well as amino acid catabolism is important for cheese flavour development.
The objective of this study was to examine the peptidolytic activity of different strains of Lb. helveticus.

Materials & methods
Seven different strains of Lb. helveticus were selected on the basis of their rep-PCR profiles. The seven different strains were Lb. helveticus CNRZ32, Lb. helveticus CNRZ303, Lb. helveticus LHC2, Lb. helveticus ATCC15009 and Lb. helveticus L100 and two strains isolated from the cheeses Arla Kadett and Cougar Gold respectively.
The bacterial strains were grown in MRS and cell free extracts were prepared using a French Press. The peptidolytic activity of the cell free extracts was measured using synthetic substrates (p-nitroanilides).

Results
The highest activity expressed by all strains was observed towards Gly-Pro-pNA, Lys-pNA and Leu-pNA. Moderate activity was observed against Bz-Phe-Val-Arg-pNA, Pro-pNA and Gly-pNA while the lowest activity was observed for Phe-pNA and Glu-pNA. Additionally, significant strain variations were observed.

Conclusion
The Lb. helveticus strains all possessed general aminopeptidases, peptidases with proline activity and endopeptidases and the activity level was strain dependent.

Acknowledgement
This study was kindly supported by the Danish Dairy Research Foundation, Arla Foods Innovation and Thise Mejeri.

Presented Wednesday 19, 13:30 to 15:00, in session Innovations in Food Technology - Poster Session (LMC/Food - P1).