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Comparison of proteolytic activities in various lactobacilli
M Sasaki1, B W Bosman, P S Tan
1Snow Brand European Research Laboratories BV, AN Groningen, The Netherlands.
The Journal of Dairy Research
|November 1, 1995
Summary
Lactobacillus and Lactococcus lactis strains exhibit varied peptidase activities. Lactobacillus helveticus showed the highest activity, while Lb. fermentum and Lb. brevis were weakly proteolytic.
Area of Science:
- Food Microbiology
- Enzymology
- Dairy Science
Background:
- Lactobacillus and Lactococcus lactis are key bacteria in dairy fermentation.
- Peptidases play crucial roles in flavor development and protein breakdown in milk products.
- Understanding the peptidase profiles of these bacteria is essential for optimizing dairy fermentation.
Purpose of the Study:
- To evaluate and compare the peptidase activities of various Lactobacillus species and Lactococcus lactis strains.
- To identify strains with high proteolytic potential for dairy applications.
- To investigate the diversity of peptidase enzymes within and between these bacterial groups.
Main Methods:
- Isolation of 169 Lactobacillus strains (12 species) and 9 Lactococcus lactis strains from raw milk and dairy products.
- Assay of cell-free extracts for peptidase activity using five chromogenic substrates and a tryptic digest of casein.
- Comparative analysis of hydrolytic activities across different species and strains.
Main Results:
- Significant variations in peptidase activity were observed among strains within the same species and between Lactobacillus and Lactococcus lactis.
- Lactobacillus helveticus demonstrated the highest hydrolytic activity across all tested substrates, indicating potent aminopeptidases, X-prolyl-dipeptidyl aminopeptidases, and proline iminopeptidases.
- Lactobacillus delbrueckii subsp. bulgaricus showed high activity towards proline-containing substrates. Lactobacillus fermentum and Lactobacillus brevis exhibited weak proteolytic activity.
- Lactobacillus strains generally had lower hydrolytic action on glutamyl-glutamic acid compared to Lc. lactis, suggesting a lack of glutamyl aminopeptidase.
Conclusions:
- Peptidase activity is highly variable among Lactobacillus and Lactococcus lactis strains, offering opportunities for strain selection in dairy processing.
- Lactobacillus helveticus and Lactobacillus delbrueckii subsp. bulgaricus are promising candidates for applications requiring high proteolytic activity.
- The absence of significant glutamyl aminopeptidase in lactobacilli warrants further investigation for specific dairy fermentation processes.